ABSTRACT
Following continuous dilation of the uterine cervix or intravenous infusion of vasopressin during the first trimester of human pregnancy, a marked increase in the peripheral plasma progesterone levels was observed. This effect was blocked by simultaneous administration of propranolol (Inderal®), a β-blocking agent. It is suggested that both these stimulating and inhibiting effects might be related to 3′, 5′-adenosine monophosphate (cyclic AMP). The results indicate the existence of β-receptors in steroid producing tissues.
