Effects of verapamil and BAY K8644 on the hypoxic contraction of the isolated human pulmonary artery.

Abstract
To examine the effect of hypoxia on the human pulmonary artery (HPA), HPA segments (2 mm, o.d.) were suspended and changes in isometric force with hypoxia (PO2 = 44 .+-. 3 mmHg, mean .+-. S.E.) were measured. HPA contracted with hypoxia and the tension developed with 15 min of hypoxia was 127 .+-. 36 (mean .+-. S.E.) mg. Verapamil at 10-6 M inhibited and 10-6 M BAY K 8644 enhanced the hypoxic response by 47 .+-. 10% (p < 0.01) and 396 .+-. 106% (p < 0.05), respectively, compared with preceding values. These results show that activation of voltage-dependent Ca2+ channels also plays an important role in the mechanism of hypoxic pulmonary vasoconstriction in man.