Journal of Applied Physiology, Vol 65, Issue 2 776-781, Copyright © 1988 by American Physiological Society
Blood-brain barrier to hydrogen ion during acute metabolic acidosis in piglets
L. C. Wagerle, S. P. Kumar, J. Belik and M. Delivoria-Papadopoulos
Department of Physiology, University of Pennsylvania School of Medicine, Philadelphia 19104.
The present study investigates the integrity of the blood-brain barrier to
H+ or HCO3- during acute plasma acidosis in 35 newborn piglets anesthetized
with pentobarbital sodium. Cerebrospinal fluid acid-base balance, cerebral
blood flow (CBF), and cerebral oxygenation were measured after infusion of
HCl (0.6 N, 0.191-0.388 ml/min) for a period of 1 h at a constant arterial
PCO2 of 35-40 Torr. HCl infusion resulted in decreased arterial pH from
7.38 +/- 0.01 to 7.00 +/- 0.02 (P less than 0.01). CBF measured by the
tracer microsphere technique was decreased by 12% from 69 +/- 6 to 61 +/- 4
ml.min-1.100 g-1 (P less than 0.05). Infusion of 0.6 N NaCl as a hypertonic
control had no effect on CBF. Cerebral metabolic rate for O2 and O2
extraction was not significantly changed from control (3.83 +/- 0.20
ml.min-1.100 g-1 and 5.7 +/- 0.6 ml/100 ml, respectively) during acid
infusion. Cerebral venous PO2 was increased from 41.6 +/- 2.1 to 53.8 +/-
4.0 Torr by HCl infusion (P less than 0.02) associated with a shift in
O2-hemoglobin affinity of blood in vivo from 38 +/- 2 to 50 +/- 1 Torr.
Cisternal cerebrospinal fluid pH decreased from 7.336 +/- 0.014 to 7.226
+/- 0.027 (P less than 0.005), but cerebrospinal fluid HCO3- concentration
was not changed from control (25.4 +/- 1.0 meq/l). These data suggest that
there is a functional blood-brain barrier in newborn piglets, that is
relatively impermeable to HCO3- or H+ and maintains cerebral perivascular
pH constant in the face of acute severe arterial acidosis. (ABSTRACT
TRUNCATED AT 250 WORDS)
