Progesterone receptors and ventilatory stimulation by progestin

ceptors and ventilutory stimulation by prugestin. J. Appl. Phys-iol. 60f2): 590-595, 1986.-Progestin is thought to be a venti-latory stimulant but its effectiveness in raising ventilation is variable in humans and other species. We hypothesized that the level of progesterone receptors was an important determi-nant of the ventilatory response to progestin. Since estradiol induces progesterone receptor formation, we compared the ventilatory effect of the synthetic progestin medroxyprogester-one acetate (MPA) given in combination with estradiol with the effects of estradiol alone, MPA alone, or vehicle (saline) in ovariectomized rats. Animals receiving MPA alone had low numbers of progesterone receptors (2.43 pmol/g uterine wt) and had no change in ventilation, arterial Pco~, or POT. MPA administration raised ventilation 23 t 5%, lowered arterial Pcoz 3.2 t 0.9 Torr (both P < 0.01) and tended to raise arteria