Vol. 92, Issue 3, 997-1003, March 2002
Therapeutic effects of DCDDP, a calcium
channel blocker, on chronic pulmonary hypertension in rat
Zhi-Chao
Li,
Fu-Qin
Zhang,
Jing-Chun
Song,
Qi-Bing
Mei, and
De-Hua
Zhao
Department of Pathophysiology, Fourth Military Medical University,
Xi'an 710032, China
 |
ABSTRACT |
To explore the effect of
dimethyl
4-(2-chlorophenyl)-1,4-dihydro-2,6-dimethyl-3,5-pyridinedicarboxylate
(DCDDP) on pulmonary hypertension (PH) induced by
monocrotaline (MCT), the parameters of pulmonary hemodynamics, the
contents of endothelin-like immunoreactivity, nitric oxide (NO),
malondialdehyde, and superoxide dismutase in plasma and pulmonary
homogenate were measured. DCDDP was administered in 5, 50, and 500 µg · kg
1 · day1
ip doses, once a day for 28 days. The antiserotonin effect of DCDDP
was investigated by using immunohistochemistry, image analysis, and
cell culture technique. The results showed that pulmonary arterial
pressure was significantly dropped and pulmonary resistance was
decreased in DCDDP groups, compared with the MCT group. DCDDP had no influence on endothelin-like immunoreactivity levels in plasma
and pulmonary homogenate but reduced the contents of NO, superoxide
dismutase, and malondialdehyde in pulmonary homogenate enhanced by MCT.
DCDDP also significantly inhibited the increase in numbers of
5-hydroxytryptamine (5-HT) and 5-HT receptor-positive cells in
pulmonary tissue of PH rats induced by MCT. The proliferation and
contraction of pulmonary arterial smooth muscle cells and the increase
in concentration of free Ca2+ in them evoked by 5-HT were
inhibited significantly by DCDDP. The results suggest that
DCDDP reduces the production of free radicals and content of 5-HT
and 5-HT receptor and the increase in NO in pulmonary tissue, which
underlies the mechanisms of DCDDP against MCT-induced PH.
5-hydroxytryptamine; calcium ion channel blocker; pulmonary artery; monocrotaline
| |
INTRODUCTION |
PULMONARY
HYPERTENSION (PH) has been widely investigated, but its
pathogenesis and therapeutics are still not clear (8). In
clinics, Ca2+ channel blockers are effective drugs for the
acute PH and acute attack of the chronic PH. However, the
Ca2+ antagonist is not satisfactory in the treatment of
chronic PH because of the side effect of decreased systemic blood
pressure and the limit for long-term administration (7).
The inhalation of nitric oxide (NO) at a lower concentration can
selectively relax pulmonary arteries and decrease pulmonary circulation
pressure and resistance (9), but special instruments are needed.
Dimethyl
4-(2-chlorophenyl)-1,4-dihydro-2,6-dimethyl- 3,5-pyridinedicarboxylate
(DCDDP) is one of the dihydropyridine calcium channel blockers.
Mahmoudian and Richards (18) reported that DCDDP could
relax ileal smooth muscle in preparations. Bossert and Vater
(1) found that DCDDP could also relax systemic
vascular smooth muscle and depress the systemic circulating pressure.
However, the underlying mechanism of DCDDP on the systemic vascular
smooth muscle is still unclear. We hypothesize that, during chronic PH, DCDDP could intensify relaxation of pulmonary vascular smooth muscle by blocking Ca2+ from entering the pulmonary
vascular smooth muscle cells and reducing free radicals, thereby
inhibiting the response of the pulmonary artery to the constricting
factors. The present study was designed to explore the therapeutic
effect and elucidate the mechanism on long-term use of DCDDP on
chronic PH induced by monocrotaline (MCT) in the rat.
| |
METHODS |
Animals and treatment protocol.
The experiments were performed on male Sprague-Dawley rats, weighing
between 180 and 220 g at the age of 8 wk (from Laboratory Animal
Center of Fourth Military Medical University, Xi'an, China). The
animals were randomly divided into six groups. In the control (Ctl)
group (n = 10), the rats were treated with saline
(single subcutaneous injection). In the MCT group (n = 10), the rats were injected subcutaneously with 60 mg/kg MCT once a day
for 28 days. In the three DCDDP groups (n = 8 each), DCDDP was applied in 5 [low (DCDDPL)], 50 [medium (DCDDPM)], and 500 µg/kg doses [high (DCDDPH)], respectively. DCDDP was administered
intraperitoneally 30 min before and after MCT injection once a day for
28 days. In the nitrendipine (NIT; Sigma Chemical) group
(n = 10), 10 mg/kg NIT, as a positive control drug,
which can effectively reduce the pulmonary arterial pressure (Ppa), was
administered intraperitoneally 30 min before and after MCT injection
once a day for 28 days.
To make the MCT solution, 200 mg of MCT were first dissolved in 1.2 ml
of 1 M HCl and then diluted with distilled water to ~5 ml and
neutralized with 0.5 M NaOH. The total volume was adjusted to 10 ml
with distilled water. DCDDP was synthesized by our laboratory. The
structure of DCDDP was confirmed with mass spectrometry and nuclear
magnetic resonance spectrometry, and the purity was measured as >98%
by HPLC. For experimental use, DCDDP was dissolved in dimethyl
sulfoxide and diluted with a mixture of ethanol, polyethyleneglycol, and distilled water (1.5:3.0:5.5).
Measurement of hemodynamics and right ventricular hypertrophy.
The animals were anesthetized with urethane (1 g/kg ip) and placed on
an animal respirator after 4 wk of MCT injection. Carotid arterial
pressure (CAP; stands for systemic arterial pressure), Ppa, and
pulmonary blood flow (PBF) were recorded by a microcomputer via
transducers. CAP and Ppa were obtained through catheterizations of the
carotid artery and the main pulmonary artery separately. PBF was
recorded at the ascending aorta using a blood flowmeter (MF2100,
Japan). Pulmonary vascular resistance (PVR) was calculated using the
formula PVR = Ppa/PBF. Right ventricular hypertrophy was estimated
by the ratio of the right ventricular (RV) weight to the sum of the
left ventricular and septal weights.
Measurement of endothelin-like immunoreactivity and
NO.
To determine endothelin (ET)-1 of the plasma and pulmonary homogenate,
each blood sample was placed in chilled tubes containing 30 µl of
10% EDTA · 2Na and 20 µl of aprotinin and centrifuged at 900 g for 10 min at 4°C. The plasma was stored at 
40°C.
For the measurement of ET-like immunoreactivity (ir-ET), 10 mg of right
lower lung tissue were placed in a tube containing 1 ml of 1 M acetic
acid, boiled for 10 min, and homogenized for 1 min. The homogenate was
then centrifuged at 900 g for 15 min at 4°C. The
supernatant was diluted with phosphoric acid buffer and stored at
40°C. ir-ET levels of the plasma and pulmonary homogenate were
measured by RIA (10) (RIA kit was purchased from the
institute of Eastern Asia, General Hospital of PLA, China).
Each blood sample was placed in heparinized tubes and centrifuged at
900 g for 20 min to obtain the plasma. The 10 mg of lung tissue were homogenized with a homogenizer for 1 min in 1 ml of saline,
and the homogenate was centrifuged at 900 g for 20 min. The
method of Inoue et al. (13) was employed to measure the contents of NO in the plasma and pulmonary homogenate.
Measurement of superoxide dismutase and malondialdehyde.
Venous blood samples anticoagulated with heparin were centrifuged at
900 g for 15 min at 4°C to obtain the plasma. Pulmonary tissue taken from the right lower lung (adding 1 ml of cold saline) was
homogenized with a homogenizer in an ice water bath. The homogenate was
centrifuged at 900 g for 15 min at 4°C to obtain the
supernatant. The method of hydroxylamine hydrochloride
(14) and thiobarbituric acid reaction (20)
was employed to measure activities of superoxide dismutase (SOD) and
concentrations of malondialdehyde (MDA) in plasma and pulmonary
homogenate, respectively.
Remodeling of pulmonary small arteries.
A block of tissue of the left lower lung was taken and embedded in
paraffin wax by the method of Farhat et al. (5). Three sections at 4-µm thickness were prepared. One was stained with hematoxylin and eosin, the second one was stained with
Verhoeff's elastin, and the third one was DNA stained by the
method of Feulgens (26). With the use of a color image
analysis system (Quantmet 570, Leica), the number and medial thickness
of arteries (<100 µm in diameter) in 10 consecutive fields (with
0.0627 mm2 on the average) in each animal were determined.
The percentage of medial thickness of circular or quasi-circular
vessels (10 vessels/each group) was calculated. DNA content and 2c, 3c,
4c, and 5c DNA-ploid were recorded and calculated by an image analysis system.
Labeling of 5-hydroxytryptamine and 5-hydroxytryptamine receptor.
With the use of the immunohistochemistry technique, 5-hydroxytryptamine
(5-HT) and 5-HT receptor (5-HTR)-positive cells in pulmonary tissue
were labeled. The primary antibodies (anti-5-HT antibody and
anti-5-HT/anti-5-HTR antibody) were provided by Dr. W. Q. Huang,
Department of Histology and Embryology, Fourth Military Medical
University, Xi'an, China. Biotin-labeled sheep anti-rabbit antiserum
and avidin-biotin complex were from Bako. Staining procedures were
performed as described by Hsu et al. (12). In the
alternative sections, 5-HT (1:5,000) or 5-HT/5-HTR (1:100) were
incubated, respectively. In Ctl subjects, the primary antibody was
replaced with normal rabbit serum. By using the image analysis system
(Quantimet 570, Leica), the number of 5-HT and 5-HTR-positive cells was
counted in 10 consecutive fields for each slide (1 slide/rat,
n = 5). The optical density level was also determined
with software of the image analysis system (Quic; at ordinary light and
blue light filter) from a total of 150 5-HT and 5-HTR-positive cells
(30 cells/rat, n = 5).
Culture of pulmonary arterial smooth muscle cell.
Pulmonary arterial smooth muscle cells (PASMCs) of rat were cultured by
the method of Chamley-Campbell et al. (3). Male Sprague-Dawley rats weighing between 100 and 110 g
(n = 8) were anesthetized with pentobarbital sodium (30 mg/kg, administered ip). The heart and lung were extracted using a
sterile technique and put in a culture dish with D-Hanks' fluid
(Hanks' solution free of calcium and magnesium anion). The
extrapulmonary artery was isolated, and the endothelium was removed.
After two washes with D-Hanks' fluid, the middle lamella smooth muscle
was cut into 1-mm3 blocks, which were cultured using the
method of Chamley-Campbell et al. PASMCs reached confluence in 4-6
days in medium RPMI-1640 with 20% fetal calf serum (FCS). Cells used
for these studies were between passages 3 and 6.
Unless otherwise noted, the culture medium was replaced every other day
with fresh RPMI-1640 containing 10% FCS.
Functional experiment on cultured PASMCs.
The passage 3 PASMCs were enzymatically removed from the
surface with 0.3% trypsin. The cellular suspension was uniformly placed in 12-well tissue culture clusters with cover glass and cultured
for 48 h. The confluent PASMC monolayers (from the same rat) were
exposed to a single administration of 5-HT (10 µM) with or without
DCDDP (1, 10, or 100 nM) for 30 min. After the medium fluid was
absorbed, the adherent cells on the cover glass were stained with 1%
of eosin, and the length was measured with the microscope
(24).
Proliferation experiment of PASMCs.
PASMCs from passages 3-6 were placed with a density of
~5,000 cells/well in 96 multiwell plates and cultured for 24 h.
The culture medium was then replaced with fresh RPMI-1640 containing 5% FCS added with 10 µM 5-HT (final concentration). The effect of
DCDDP and NIT on the proliferation enhanced by 5-HT was observed using the dosages of 1, 10, and 100 nM with 5-HT. Proliferation of
PASMCs was measured by performing the
3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT;
thiazolyl blue) microculture tetrazolium colorimetric assay based on
the ability of viable cells to reduce the MTT compound to a blue
formazan product. After 44 h of culturing, the cellular culture
medium was added, 20 µl of 0.5% MTT. After 24 h, the cell culturing was continued for an additional 4 h in a new medium with
the same concentration of DCDDP, NIT, or 5-HT. Finally, the culture
medium was aspirated from each well and vibrated in 150 µl of
dimethyl sulfoxide for 10 min. Absorbance of each well was determined
by enzyme-linked ELISA at 490 nm of wavelength.
Measurement of free
Ca2+ in cultured
PASMCs.
PASMCs from passages 3-6 were placed in six multiwell
plates and cultured for 24 h. The culture medium was replaced with
fresh RPMI-1640 containing 5% FCS. The effect of 5-HT (10 µM) with
and without DCDDP (10 nM) or NIT (10 nM) on the intracellular free Ca2+ concentration was assessed. DCDDP or NIT was added
and preincubated in cultured PASMCs for 30 min before 5-HT treatment.
The cell monolayer was washed twice with sterile
Ca2+-Mg2+-free Hanks' balanced salt solution
to remove nonadherent cells. The adherent cells were enzymatically
removed from the surface with 0.3% trypsin and adjusted to the density
of ~2 × 109 cells/l. The cell survival rate was
>90%, which was determined by trypan blue exclusion reaction. One
milliliter of cellular suspension was incubated with 10 µM fura
2-acetoxymethyl ester (final concentration) at 37°C for 45 min and
then centrifuged at 100 g for 5 min. After the supernatant
was abandoned, the cells were rinsed twice with sterile
Ca2+-Mg2+-free Hanks' balanced salt solution.
Finally, 1 ml of cellular suspension was incubated for 10 min, and the
concentration of free Ca2+ in PASMCs was determined by
fluorophotometry (22).
Statistics.
All data are expressed as means ± SD. Group means were compared
using an unpaired Student's t-test. A value of
P < 0.05 was accepted as statistically significant.
| |
RESULTS |
Changes in pulmonary hemodynamics.
MCT greatly affected the mean Ppa (MPAP) and PVR in the
experimental rats (Table 1).
After 28 days of administration of MCT, MPAP was increased by 114%
(2.1 ± 0.4 kPa in Ctl vs. 4.5 ± 0.9 kPa in MCT;
P < 0.05), whereas PVR was elevated by 162% (45 ± 10 kPa · min1 · l1 in
Ctl to 118 ± 17 kPa · min1 · l1 in MCT;
P < 0.05). DCDDP could effectively block the
effect of MCT on the MPAP and PVR. Compared with the MCT group, the
MPAP was reduced by 29, 23, and 16% in DCDDPL,
DCDDPM, and DCDDPH groups (P < 0.05), respectively. Meanwhile, PVR dropped by
45, 42, and 36%, respectively, in these three DCDDP groups
(P < 0.05). NIT had a similar effect on the pulmonary
hemodynamics, as DCDDP did. The mean CAP and PBF were not
significantly affected by DCDDP and NIT (Table 1).
Effects on contents of ir-ET, MDA,
NO, and activity of SOD.
In the MCT group, the content of ir-ET and NO was dramatically
increased in plasma (P < 0.05) (Fig.
1) but decreased in pulmonary homogenate,
compared with that in the Ctl group. In both venous plasma and
pulmonary tissue, the content of MDA was significantly increased,
whereas the activity of SOD dramatically decreased. DCDDP did not
affect the content of ir-ET in either plasma or pulmonary tissue.
Compared with that in the MCT group, in all three DCDDP groups, the
NO level was decreased in plasma but increased in pulmonary tissue; the
content of MDA was reduced to normal levels in pulmonary tissue but
remained high in plasma. DCDDP also significantly elevated the
activity of SOD in both plasma and pulmonary homogenate. After NIT
treatment, the effects on ir-ET, NO, MDA, and SOD were basically
similar to those produced by DCDDP (Figs.
1-4).
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Fig. 1.
Effects of dimethyl
4-(2-chlorophenyl)-1,4-dihydro-2,6-dimethyl-3,5-pyridinedicarboxylate
(DCDDP) on the contents of endothelin-like immunoreactivity (ir-ET)
and nitric oxide (NO) in plasma. Experimental groups: 1, control (Ctl);
2, monocrotaline (MCT); 3, low-dose DCDDP (5 µg/kg;
DCDDPL); 4, medium-dose DCDDP (50 µg/kg;
DCDDPM); 5, high-dose DCDDP (500 µg/kg;
DCDDPH); 6, nitrendipine (NIT). * Significant
difference frome Ctl (P < 0.05); # significant
difference from MCT (P < 0.05).
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Fig. 2.
Effects of DCDDP on the contents of superoxide
dismutase (SOD) and malondialdehyde (MDA) in plasma. Experimental
groups are as described in Fig. 1 legend. * Significant difference
from Ctl (P < 0.05); # significant difference from
MCT (P < 0.05).
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Fig. 3.
Effects of DCDDP on the contents of ir-ET and NO in
pulmonary homogenate. Experimental groups are as described in Fig. 1
legend. * Significant difference from Ctl (P < 0.05); # significant difference from MCT (P < 0.05).
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Fig. 4.
Effects of DCDDP on the contents of SOD and MDA in
pulmonary homogenate. Experimental groups are as described in Fig. 1
legend. * Significant difference from Ctl (P < 0.05); # significant difference from MCT (P < 0.05).
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Effects of DCDDP and NIT on the
pulmonary artery and DNA in PASMCs.
After 4 wk of MCT treatment, there were a number of inflammatory cells
in which monocytes and lymphocytes were predominant around vascular
vessels. MCT made the walls of the small pulmonary artery (<100 µm
in diameter) thicker. The average percent ratio of medial thickness to
vessel diameter of 10 circular vessels increased by ~70% in the MCT
group (Table 2). DCDDP had an
inhibitory effect on the change in thickness produced by MCT. In the
MCT group, DNA contents of PASMCs and the percentage of 3c to 4c
DNA-ploid were significantly increased, compared with that in the Ctl
group. DCDDP eliminated DNA changes in PASMCs produced by MCT
(Table 3). NIT also had a similar reverse
effect on the thickness of small pulmonary arteries and DNA contents in
PASMCs (Tables 2 and 3).
Effects of DCDDP and NIT on
5-HT.
In MCT-induced PH, 5-HT-positive cells in pulmonary tissue were
tremendously enhanced (0.004 ± 0.002 cells/µm2 in
Ctl vs. 0.127 ± 0.021 cells/µm2 in MCT;
P < 0.05); 5-HTR-positive cells also significantly
increased but to a lesser extent (0.003 ± 0.001 cells/µm2 in Ctl vs. 0.015 ± 0.003 cells/µm2 in MCT; P < 0.05). The
relative contents of 5-HT and 5-HTR-positive cells expressed with
optical density value also significantly increased (Table
4). Both DCDDP and NIT greatly
reduced the number of positive cells and the amount of 5-HT and 5-HTR
induced by MCT, but they were still higher than those in the Ctl group
(Table 4).
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Table 4.
Effects of DCDDP on the numbers and relative content of 5-HT and
5-HTR-positive cells in pulmonary tissue in MCT-induced PH
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Effects of DCDDP and NIT on
proliferation, constriction, and free
Ca2+ content of PASMC.
MTT reduction assay showed that 5-HT could induce hyperplasia and
constriction of PASMCs. After 10 µM 5-HT treatment, the absorbance at
490 nm of wavelength of PASMCs was elevated by 38%, from 0.098 ± 0.021 (in Ctl) to 0.135 ± 0.008 (P < 0.05).
DCDDP and NIT had a reverse effect on 5-HT to varying extents,
compared with that in the Ctl group (Table
5).
After administration of 10 µM 5-HT, the average length of PASMCs
shortened from 184 ± 49 µm (in Ctl) to 106 ± 23 µm
(P < 0.05). DCDDP (10 and 100 nM) downregulated
pulmonary arterial constriction produced by 5-HT by 25-30%
(P < 0.05), compared with the length of 5-HT-treated
PASMC (Table 5). However, NIT had only a weak effect (Table 5).
After the treatment with 10 µM 5-HT in cultured PASMCs, the
intracellular free Ca2+ concentration increased by
~150%, compared with that in the Ctl group. This effect could be
partially blocked by either DCDDP or NIT. DCDDP (10 nM) and NIT
(10 nM) reduced the intracellular free Ca2+ concentration
by ~50% (Fig. 5).
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Fig. 5.
Effects of DCDDP and NIT on the intracellular
concentration of Ca2+ ([Ca2+]) induced by
5-hydroxytryptamine (5-HT) in cultured pulmonary arterial smooth muscle
cells (PASMCs). * Significant difference from Ctl (P < 0.05); # significant difference from pure 5-HT-treated group
(P < 0.05).
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| |
DISCUSSION |
The MCT-induced PH is an ideal animal model for investigating the
mechanism on PH (11, 18). PH is characteristic of the remodeling and abnormal response of pulmonary vessels. In the present
study, the dramatic changes in morphology and functional metabolism of
pulmonary vessels were observed in MCT-induced PH, such as the increase
in MPAP and PVR, the wall thickness of the right ventricle, the
thickness of small pulmonary arterial vessels, and DNA contents in
PASMCs as well. DCDDP could modify the changes in pulmonary
hemodynamics and morphology in MCT-induced PH and restore the content
of DNA to the normal level. Basically, NIT had a similar effect as
DCDDP did on chronic PH. The therapeutic effects of DCDDP could
be related to relaxing the PASMCs, protecting endothelial cells from
damage, and inhabiting the DNA synthesis of PASMCs as well.
Vascular endothelial cells play an important role in regulating the
vascular smooth muscular tension by releasing NO and ET. Dysfunction of
vascular endothelial cells is associated with the development of PH.
Changes in ET, NO, MDA, and SOD activity in plasma and pulmonary tissue
were observed in MCT-induced PH in the present study. Vascular
endothelial cells are the main origin of ET and NO in the normal
condition. Our study showed that the content of ir-ET and NO was
dramatically increased in plasma but decreased in pulmonary homogenate
in the MCT group, compared with that in the Ctl group. We speculate
that the differences might be caused by selective roles of MCT, which
damage pulmonary vascular endothelial cells but only stimulate systemic
vascular endothelial cells. Our experimental data show that damages of
pulmonary endothelial cells are more serious than those of systemic
endothelial cells, such as abdominal artery and renal artery, which
may, at least in part, explain the differences in ir-ET and NO between
plasma and pulmonary homogenate. But the detailed causes of these
differences in ir-ET and NO between plasma and pulmonary homogenate
need to be studied further. The change in ET and NO was out of
proportion in pulmonary tissues, and NO content was decreased much more
(97%), compared with ET (49%), from control. Functionally, the
injured pulmonary vascular endothelial cells can impair the formation and metabolism of NO. The dramatic decrease in activity of SOD and
increase in content of MDA in venous plasma and pulmonary homogenate
indicated an enhanced production of free radicals [especially superoxide anion (O
·)] and an intensified lipid
peroxidation response. Because SOD is a scavenger of
O·, the content of O·
increased, whereas the activity of SOD significantly decreased. The
excessive O· can not only injure vascular
endothelial cells and inhibit NO generation, but also inactivate NO
(16,21) and produce a more poisonous free radical,
peroxynitrite anion (23), by combining with NO.
Peroxynitrite anion could weaken vascular relaxation and intensify the
injury of endothelial cells. Li et al. (17) also reported
that O· can cause dose-dependent constriction of
the intrapulmonary artery. Because MDA is a product of lipid
peroxidation, the increase in MDA indicates intensification of
lipid peroxidation and the injury of the cellular membrane. In
MCT-induced PH, there were increasing numbers of inflammatory cells, in
which monocytes and lymphocytes were predominant around vascular
vessels. These inflammation cells may be the main source of free
radicals. DCDDP, a Ca2+ channel blocker, can protect
the endothelial cells from damage by intensifying the lipid
peroxidation of pulmonary tissue, which may be related to the elevated
NO and ET in pulmonary homogenate with the treatment of DCDDP in
MCT-induced PH.
In 1965, Furner and Lalich (6) proposed that 5-HT released
from mast cells could result in PH. However, Kanai et al.
(15) reported that the elevation of 5-HT in blood was only
a temporary phenomenon, and 5-HT recovered to normal levels within 3 days after subcutaneous injection of MCT. The response to 5-HT in the pulmonary artery was stronger in MCT-induced PH, which suggested that
the density of 5-HTRs in the pulmonary artery be upregulated. Our
experiment provided further evidence that both 5-HT and 5-HTR-positive cells and their relative contents in lung tissue were significantly increased after 4 wk of treatment with MCT in PH. 5-HT can produce proliferation of pulmonary small vessels, either directly or
indirectly, by stimulating alveolar macrophage. In cell culture, 5-HT
was also found to enhance the constriction and proliferation of PASMCs, while the level of Ca2+ in PASMCs was elevated. All of
these results suggest that the increase in the amount of 5-HTRs in
pulmonary tissue underlies the mechanism by which the pulmonary artery
response to 5-HT was intensified in MCT-induced PH.
It has been reported that NIT could inhibit constriction of sheep
pulmonary arterial strip produced by 5-HT (4). Felodipine could increase relaxation of the pulmonary artery in MCT-induced PH in
rat (25) and improve pulmonary hemodynamics in chronic obstructive pulmonary disease, at least in part, by decreasing the
maximum constriction effect of the human pulmonary artery to 5-HT
(19). The present study showed that both DCDDP and NIT can not only reduce pulmonary arterial constriction and proliferation induced by 5-HT at 10 µM, but also decrease 5-HT and 5-HTR-positive cells in lung tissue. The function of DCDDP is attributed to
protecting the endothelial cells, in which 5-HT is decomposed and
decreasing the Ca2+ concentration in PASMCs. These
effects are the therapeutic mechanisms of DCDDP in MCT-induced PH.
In summary, as a Ca2+ channel blocker, DCDDP is a more
effective drug than NIT for PH induced by MCT in rat. The mechanism of DCDDP for treatment is that DCDDP can protect predominantly the endothelial cells from injury by a free radical derived from lipid peroxidization. DCDDP is also related to the alteration of 5-HT metabolism and PASMCs response to 5-HT, as well as the dysfunction of
the Ca2+ channel.
| |
ACKNOWLEDGEMENTS |
The authors are grateful to Drs. Wen-Zhi Zhan, Ben-Tao Sun, and
Wen-Quan Huang for comments on the manuscript and for assistance in
some of the studies.
| |
FOOTNOTES |
This research was supported by grants from the Fourth Military Medical University.
Address for reprint requests and other correspondence: Z.-C.
Li, Dept. of Pathophysiology, Fourth Military Medical Univ., Xi'an
710032, China (E-mail: Lizhic{at}fmmu.edu.cn).
The costs of publication of this
article were defrayed in part by the
payment of page charges. The article
must therefore be hereby marked
"advertisement"
in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
10.1152/japplphysiol.00237.2001
Received 13 March 2001; accepted in final form 12 November 2001.
| |
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