Perinatal History of Hypoxia Leads to Lower Vascular Pressures and Hyporeactivity to Angiotensin II in Isolated Lungs of Adult Rats
V. Hampl, J. Bíbová, J. Herget
Department of Physiology, Second Faculty of Medicine, Charles University,
Prague, Czech Republic
Received February 29, 2000
Accepted April 3, 2000
Summary
The most dramatic changes in pulmonary circulation occur at
the time of birth. We hypothesized that some of the effects of perinatal hypoxia
on pulmonary vessels are permanent. We studied the consequences of perinatal
exposure to hypoxia (12 % O2 one week before and one week after
birth) in isolated lungs of adult male rats (~12 weeks old) perfused with
homologous blood. Perfusion pressure-flow relationship was tilted towards lower
pressures in the perinatally hypoxic as compared to the control, perinatally
normoxic rats. A non-linear, distensible vessel model analysis revealed that
this was due to increased vascular distensibility in perinatally hypoxic rats
(4.1±0.6 %/mm Hg vs. 2.3±0.4 %/mm Hg in controls, P = 0.03).
Vascular occlusion techniques showed that lungs of the perinatally hypoxic rats
had lower pressures at both the pre-capillary and post-capillary level. To
assess its role, basal vascular tone was eliminated by a high dose of sodium nitroprusside (20 µM). This reduced perfusion pressures only in the lungs of
rats born in hypoxia, indicating that perinatal hypoxia leads to a permanent
increase in the basal tone of the pulmonary vessels. Pulmonary vasoconstrictor
reactivity to angiotensin II (0.1-0.5 µg) was reduced in rats with the history
of perinatal hypoxia. These data show that perinatal hypoxia has permanent
effects on the pulmonary circulation that may be beneficial and perhaps serve to
offset the previously described adverse consequences.
Key words
Perinatal hypoxia · Vascular
pressure · Pulmonary circulation · Angiotensin II
Reprint requests
Dr. V. Hampl, Department of Physiology, Second Faculty of
Medicine, Charles University, Plzeňská
130/221, 150 06 Prague 5-Motol, Czech Republic, e-mail: vaclav.hampl@lfmotol.cuni.cz
|