Developmental changes in the response of male and female rat pituitary to LH-RH in vitro

Changes in the binding of 125I-LH-RH and the sensitivity of male and female rat pituitary of LH-RH were measured in vitro from the 5th to 60th day of age. Pituitaries of all the age groups were responsive to LH-RH. Two phases of pituitary sensitivity to LH-RH could be detected in both the male and female rat. The first phase or the period of low sensitivity extended up to the day 14, while the second one or the period of high sensitivity started from the day 15 onwards. During the second period the sensitivity of female pituitary to LH-RH was significantly higher than that of male one. In the female pituitary the changes in the sensitivity to LH-RH were parallel to changes in 125I-LH-RH binding. However, in the male pituitary 125I-LH-RH binding was higher while the sensitivity of pituitary to LH-RH was compatively lower than in the female rat. It is postulated that two different types of receptors may be involved in the stimulation of LH-RH induced LH release from the male and female pituitary.