Mechanisms of Maintenance of Corpora Lutea in Pigs and Rats

Summary. Luteal cells were obtained by digestion of luteal tissue of cyclic (day 12) and early pregnant (days 12, 20 and 30) pigs. Suspensions of the dispersed luteal cells (5 x 104 cells ml \m=-\1) were incubated for 2 h in minimum essential medium (MEM) alone (control) and MEM with different concentrations of prostaglandin FF2\ g=a\(PGF2\g=a\) and PGE2 (0\m=.\01,0\m=.\1,1, 10, 100 and 1000 ng ml \m=-\1) and luteinizing hormone (LH) 100 and 1000 ng ml\m=-\1, or with combinations of LH+ PGF2\g=a\and LH + PGE2. Net progesterone production was measured in the incubation media by direct radioimmunoassay.The overall response pattern of the luteal cells to exogenous hormones on day 12 of the oestrous cycle and pregnancy differed (P < 0\m=.\5) from treatment on day 20 and 30 of pregnancy. In general progesterone production was higher (P < 0\m=.\5) and the response to PGF2\g=a\ and PGE2 treatment was most obvious on day 12 of the oestrous cycle and pregnancy. Overall, PGF2\g=a\ stimulated progesterone production in a dosedependent manner (P < 0\m=.\05). The response to PGE2 was of a quadratic nature (P < 0\m=.\05) in which the lowest and the highest doses of PGE2 were associated with a greater production of progesterone than were the intermediate doses. Treatment of luteal cells with PGF2\g=a\ + LH or PGE2 + LH caused overall inhibition (P < 0\m=.\05) of progesterone production compared with treatment with each hormone alone. This interaction was not affected by the dose of LH used.These findings indicate that PGF2\g=a\ and PGE2 are involved in the autocrine control of corpus luteum function.

Section: Introductionmentioning

confidence: 99%

Effect of prostaglandins on luteal function during early pregnancy in pigs

Więsak

Hunter²,

Foxcroft³

1992

“…decidual tissue) were occasionally able to maintain gestation in L6 hypophysectomized pregnant rats. Nalbandov (1961) and Semmelwitz, Aldred & Nalbandov (1961) put forward the hypothesis that a factor of uterine origin maintains the life of corpora lutea of both pregnant and pseudopregnant rats. But, so far, no investigations have been reported on the effect of decidualization (experi¬ mentally produced) on corpora lutea in hypophysectomized animals and thus to find out whether such corpora lutea are able to maintain the deciduomata.…”

Section: Introductionmentioning

confidence: 99%

Studies on the Mechanism of Nidation

Varavudhi¹,

Bl²,

Mc³

1966

“…In a companion paper (Sammelwitz, Aldred & Nalbandov, 1961), experi¬ mental data are presented which suggest that the growth of corpora lutea in normal oestrous cycles of pigs and rats is governed by a single release of hypo¬ physeal luteotrophic hormone (lth) which seems to occur at about the time of ovulation, and that corpora lutea of cycles get no further support from hypo¬ physeal lth during their normal life span. Furthermore, these data suggest that additional hypophyseal lth release occurs if pigs become pregnant and that this release is triggered by the events of implantation in the uterus.…”

Section: Introductionmentioning

confidence: 99%

Mechanism of Formation of Corpora Lutea in Guinea-Pigs

Aldred¹,

Sammelwitz²,

Nalbandov³

1961

Self Cite

High doses of progesterone can apparently inhibit secretion or release of hypophyseal hormones, including the luteotrophic hor¬ mone (lth). Injection of progesterone into non-pregnant and pregnant guinea-pigs led to partial destruction of formed corpora lutea but did not prevent their initial formation.The data presented suggest that in the guinea-pig lth is released about the time of ovulation, but for a period of less than 3 days. This temporary release of lth is sufficient to initiate formation and function of corpora lutea. No further lth support seems to occur in non-pregnant females.In pregnant animals, a neurohumoral signalling mechanism initiated by intrauterine events of implantation is assumed to call forth a second release of hypophyseal lth, which is responsible for the maintenance of corpora lutea during the remainder of their functional life span during gestation. Prolactin is not luteotrophic in guinea-pigs.