Hypotensive effect of heparin on experimental chronic pulmonary hypertension in rats.

Daily heparin injections (300 mg s.c.) during four weeks of hypoxic exposure resulted in a smaller rise in pulmonary artery pressure as compared with otherwise nontreated rats exposed to the same regimen of hypoxia. Heparin treatment did not significantly affect the systemic arterial pressure of the hypoxic rats. In spite of the different pressure load of the right ventricle after hypoxia in treated and control rats, there was no difference in parameters indicative of the degree of right ventricular hypertrophy between these two groups of hypoxic rats. This finding suggests that the difference in pressure load between the two groups of hypoxic rats occurred late in the course of hypoxic exposure.