Action of 15-methyl-prostaglandin F2 alpha on progesterone receptors and estradiol receptors in rabbit uterus

15-Methyl-PGFiv to pseudopregnant and immature rabbits increased the amount of progesterone receptors (P-R) in uteri. The increase of P-R in pseudopregnant uteri was more marked than that in immature uteri. But no striking change of estradiol receptors and of Ka of both receptors was observed. Injection of 15-methyl-PGFto pseudopregnant rabbits decreased the plasma progesterone level, but did not enhance the spontaneous contraction of uteri.
It is suggested that 1) The mechanism of the increase of P-R in uterus is mediated mainly through the luteolytic action of 15-methyl-PGF; 2) The P-R in uterus plays a role in regluation of uterine contraction.