Effects of testosterone and its metabolites on LHRH and LH gene expression in castrated adult rats

To examine alterations in LHRH and LH gene expression in response to testosterone (T), dihydrotestosterone (DHT) and estradiol (E), LHRH mRNA level in the hypothalamus, and α and LHβ subunit mRNA levels in the anterior pituitary were simultaneously determined. T and other steroids were administered s.c. to castrated (two weeks) rats, and LHRH, α and LHβ mRNA levels were determined by RNA-blot hybridization with appropriate probes. All of the three steroids, T, DHT and E efficiently suppressed α and LHβ mRNA levels in the anterior pituitary, which were accompanied by parallel change in serum LH levels. However, DHT was only effective in decreasing LHRH mRNA level, whereas neither T nor E altered LHRH mRNA levels. The present study indicates that T and its metabolites differentially regulate LHRH and LH gene expression.