Journal of Applied Physiology, Vol 61, Issue 6 2081-2087, Copyright © 1986 by American Physiological Society
Late pulmonary responses induced by Ascaris allergen in conscious squirrel monkeys
R. Hamel, C. S. McFarlane and A. W. Ford-Hutchinson
This study presents an antigen-dependent model of biphasic pulmonary
changes to Ascaris suum in conscious squirrel monkeys. Animals with strong
positive skin reactivity towards A. suum were trained to sit quietly in
chairs and to breathe through face masks. Dynamic compliance (Cdyn) and
pulmonary resistance (RL) were measured in these conscious animals before
and for a period of 11 h after administration of an aerosol of Ascaris or
ragweed antigen. The aerosol of Ascaris antigen induced reproducible
increases (42%) in RL (P less than 0.001) and decreases (17%) in Cdyn (P
less than 0.01) that peaked respectively 5 and 35 min after antigen
challenge and lasted 60-90 min. After recovery, a second
bronchoconstriction began between 2 and 8 h and peaked between 4 and 10 h
after antigen challenge. Decreases in Cdyn (41%) were significantly greater
(P less than 0.003) whereas mean increases in RL (44%) were similar during
the late phase as compared with the first phase. The mean Cdyn decreases
lasted a minimum of 2 h, whereas RL increases lasted less than 60 min. The
time course of the responses varied from animal to animal but changes in
individual animals were reproducible over a period of 6 mo. No significant
correlation was observed between the cutaneous and the pulmonary responses
to Ascaris and the late response was not reversed by aerosol administration
of salbutamol (1.0 mg/ml). As a negative control animals were exposed to an
aerosol of ragweed extract after which no immediate or late pulmonary
response were observed. The results suggest that this primate model may be
useful to study the pathophysiology of asthma in humans.
