Correlations Between Ovarian Sensitivity, Vaginal Cyclicity and Luteinizing Hormone and Prolactin Secretion in Lightly Androgenized Rats1

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Abstract
In an investigation of the possible sequence of changes that occurs as lightly androgenized rats become sterile, a combined test of ovarian sensitivity to LH [luteinizing hormone] and the ability of gonadal steroids to facilitate LH secretion was administered to normal and androgenized rats given 10 .mu.g testosterone propionate on day 5 (to induce the delayed anovulation syndrome). Pentobarbital-blocked proestrous or similarly treated persistent estrous rats were given an i.v. injection of LH, and 1 ovary was removed the next morning for microscopic examination of tubal ova. The following morning (1000 h), estradiol benzoate was injected and a blood sample taken that afternoon (1700 h). The next morning (1000 h) progesterone was injected and blood samples were taken that and the following afternoon (both at 1700 h). The entire test was repeated in the same animals 3-4 wk later, with removal of the remaining ovary. In cycling animals (both normal controls and cycling androgenized rats), the LH induced ovulation, and the steroids induced a 24 h advance in the LH surge. Ovarian sensitivity was reduced in the persistent estrous rats in 1 experiment, but not in a 2nd. Persistent estrous rats also failed to respond to gonadal steroids with increased LH release. Androgenized rats (both cycling and persistent estrous) had higher plasma prolactin titers than did the normal animals. Changes in prolactin secretion may occur before the animal becomes sterile, while changes in LH secretion occur concomitantly with development of persistent vaginal estrus, and changes in ovarian sensitivity may occur after development of persistent estrus.