MINOXIDIL REDUCES PULMONARY VASCULAR-RESISTANCE IN DOGS AND CATTLE

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  • 1 January 1976
    • journal article
    • research article
    • Vol. 88  (6) , 885-894
Abstract
Minoxidil has a direct dilator effect on the systemic arterial smooth muscle. It is potentially an important drug in the treatment of systemic hypertension, especially when combined with .beta. blockade, which is used to control the associated tachycardia and increase in cardiac output. Because minoxidil might cause pulmonary hypertension, the acute effect of monoxidil and propranolol, separately and in combination, was examined on the pulmonary vasculature of the anesthetized dog and the awake calf during normoxia and hypoxia. In both species minoxidil reduced pulmonary vascular resistance. In the dogs this appeared to be the result of a direct action on the pulmonary vascular smooth muscle and in the cattle it was secondary to .beta.-receptor stimulation. Propranolol alone in the cattle increased the pulmonary pressor response to hypoxia. Although the possibility that chronic administration of minoxidil might cause pulmonary hypertension by some other mechanism was not examined, a reduction rather than an increase, in pulmonary vascular resistance could have occurred. Furthermore, there seems to be a species difference in the mode of its action in dogs and cattle.