Relationship between gonadotropin subunit messenger ribonucleic acid levels and plasma gonadotropin concentrations in intact and orchidectomized adult rats

To gain further insight into the factors regulating FSH, LH, and uncombined alpha subunit secretion in the male rat, pituitary levels of the gonadotropin subunit mRNAs and plasma levels of FSH, LH, and alpha subunit were measured in 7-wk-old intact male rats and rats castrated 2 wk previously. A highly positive correlation was found between pituitary FSH beta mRNA levels and plasma FSH concentrations in intact (r = 0.60; p = 0.039) but not in castrated rats (r = -0.13; p = 0.66). On the other hand, neither pituitary alpha subunit nor LH beta mRNA levels were predictive of plasma alpha subunit or LH concentrations in intact or orchidectomized rats. This observation is consistent with the proposal that a pretranslational mechanism is the major determinant of FSH secretion in the intact adult male rat but not in the castrated male.