Pituitary Responsiveness to LH-Releasing Hormone in Intact Female Rats of Different Ages*

Abstract

The pituitary responses to a purified porcine preparation of LH-releasing hormone were investigated in female rats of 15, 25, 30, 35, 45, 60, and 210 days of age. Significant amounts of LH were released after the injections of LH-RH at all the ages studied. The greatest response was observed in rats 15 and 25 days of age, and the lowest in rats 35 days of age. Pituitary LH concentration in rats injected with saline was highest in animals 15 and 25 days of age, and lowest in animals 60 days of age. Evidence of significant pituitary LH depletion after injection of LH-RH was seen only in the 25-day-old group. LH-RH induced significant release of FSH in animals 15, 25, and 30 days of age. The response was greatest, however, at 15 and 25 days of age. Pituitary FSH concentration in saline injected rats steadily declined from 15-210 days of age. No evidence of significant FSH depletion after LH-RH could be detected. (Endocrinology90: 1499, 1972)