AJP - Endocrinology and Metabolism, Vol 241, Issue 6 444-E448, Copyright © 1981 by American Physiological Society
Induction of luteolysis by dihydrotestosterone in the pregnant rat
R. Sridaran and G. Gibori
A dihydrotestosterone (DHT) pellet (4 mg) inserted under each ovarian bursa
on day 9 of pregnancy induced within 24 h, a 40% decline in serum
progesterone (P) concentrations in rats; a further reduction was observed
on days 12 and 15. Although P levels were significantly reduced by DHT
treatment, fetuses remained alive on day 12. However, by day 15, complete
abortion occurred in 75% of the rats, indicating that a decline in P
secretion precedes abortion, To further determine whether the abortifacient
action of DHT was due to its luteolytic effect, 20-cm DHT capsules were
implanted subcutaneously in ovariectomized rats treated with 4 mg P and 0.5
micrograms of estradiol (E). Control rats were sham-operated and treated
with empty capsules. DHT treatment induced complete abortion by day 15 only
in rats with ovaries present, further indicating that DHT was not directly
detrimental to the fetuses but acted on the ovaries to induce luteolysis.
When DHT treatment was started on day 12, no luteolytic effect was
detectable. To determine whether the effect of DHT was mediated by either a
decrease in the ovarian production of E, a decline in luteal cell content
of luteinizing hormone (LH) receptors or both, testosterone (T) levels in
the peripheral circulation and E and P concentrations in the ovarian vein
were measured on day 15 in rats implanted with two DHT pellets under the
ovarian bursa on day 9. Luteal content of LH receptors was also measured on
day 12 in similarly treated rats. DHT treatment had no effect on serum
levels or on ovarian vein concentration of E, but induced a significant
decrease in the ovarian vein levels of P. DHT also did not depress LH
receptor content in corpora lutea. DHT levels in the ovaries increase
significantly between days 18 and 22 of pregnancy, concomitant with the
cessation of corpus luteum function. These results indicate that DHT
possesses a potent luteolytic activity and could be involved in the
luteolytic process in the pregnant rat.
