A Study on the Effect of Progesterone on Coronary and Femoral Blood Flow in Prepubertal Female Anesthetized Dogs

This work was undertaken to study the effects of progesterone on the coronary and
femoral blood flow. In 18 prepubertal female dogs anesthetized with thiopental
sodium, changes in the coronary and femoral flow caused by intravenous infusion of
progesterone were assessed by collecting blood through Mrowtiz cannula form
coronary sinus and femoral blood through a catheter inserted inside the femoral vein
after ligation of the external iliac artery. In 6 dogs, infusion of 1 mg/kg of
progesterone increased the coronary and femoral blood flow. The vasodilator effects
of the hormone were enhanced by graded increases in the dose between 1, 2 and 3
mg/kg. The mechanisms of these responses were studied in the dogs by repeating the
experiment after the arterial blood pressure and heart rate had returned to the
control values before infusion. After administration of α blocker (phentolamine) or β
blocker( propranolol), they did not affect the responses elicited by progesterone in the
femoral blood flow. Also, injection α, β sympathetic blocker and cholinergic blocker
(atropine) did not abolish the effect of progesterone on the coronary flow. Injection of
N-nitro-L-arginine methyl ester (L-NAM) alone or with progesterone into the
coronary or the femoral artery caused prevention in the increase in the coronary and
femoral flow. The present study showed that, intravenous infusion of progesterone
dilated the coronary and the femoral arteries. The mechanism of this response did not
involve stimulation of sympathetic or parasympathetic vasodilator receptors, but may
be through the local action.