The pattern of progesterone secretion in hypophysectomized rats bearing pituitary transplants: effects of hysterectomy, estrogen, and indomethacin.

Cyclic rats were hypophysectomized and their pituitaries transplanted beneath the kidney capsule on day 2 (day 1, ovulation); they were then either hysterectomized or sham hysterectomized (uterus intact rats) and injected sc daily with either 1.0 micrograms 17 beta-estradiol (E1) or with the sesame oil vehicle until autopsy on day 105. Blood samples were drawn by jugular venipuncture every 2 to 3 days until day 21 and once weekly thereafter. In these rats the serum progesterone level rose until about day 8 and tended to reach a plateau between days 8 and 14. The regression phase began, in general, after days 8 to 14 and continued, without change in rate, for at least 3 months. In both the uterus-intact and the hysterectomized rats, E1 seemed to induce an earlier onset of regression and a brief increase in its rate, but did not otherwise affect the rate of regression. In the hysterectomized rats regression began later than in the uterus-intact rats, but its rate was also not different from the latter. The serum progesterone pattern of rats subjected to pituitary autotransplantation on day 2 was compared with that of pseudopregnant rats which were either subjected to pituitary autotransplantation on day 2, 5, 7, or 9, or were given a pituitary homotransplant on day 2, and then hypophysectomized on day 2, 3, 5, or 7. A group of rats with sham operations served as additional controls. In these rats, the same pattern of serum progesterone already described was seen in those subjected to either pituitary autotransplantation on or before day 5, or to pituitary homotransplantation, and to hypophysectomy on or before day 5. However, when the pituitary was autotransplanted on day 7 or day 9, or when the pituitary homotransplant-bearing rat was hypophysectomized on day 7, regression began earlier and was more rapid than in rats operated on on or before day 5. In fact, in the rats operated on on day 9, regression was as rapid as it was in the intact (sham operation) controls. Another group of rats subjected to pituitary autotransplantation and hysterectomy on day 2 was divided into four subgroups on day 21. In two of these, the rats received indomethacin-containing Silastic capsules inserted into each ovarian bursa; in the other two groups blank capsules were similarly inserted.(ABSTRACT TRUNCATED AT 400 WORDS)