In the present study, the diameter of the CL that developed in the absence of episodic LH pulses after the preovulatory surge of LH represented about 60% of the diameter of the CL in control females. However, secretion of progesterone from the CL of females in which episodic LH release was inhibited represented about 25% of that produced by the CL of females from the control group. Inhibition of release of LH pulses in females from Days 2 to 12 of the estrous cycle had an effect on function of the CL resulting in a decrease of about 50% in secretion of progesterone compared with values for control females.
Effects of the LHRH antagonist in inhibiting release of LH pulses likely extended over a period beyond cessation of treatment. When females are treated with LHRH antagonist from Days 2 to 7 of the estrous cycle, pulse frequency of LH is diminished for up to 10 days after cessation of treatment due to a residual effect of the antagonist. Those results were confirmed with the observations of the delayed time to return to estrus subsequent to treatment in the present study.
The possibility cannot be discounted that the LHRH antagonist may have effects directly at the ovary to inhibit development of the CL.