Castration increases luteinizing hormone subunit messenger RNA levels in male rat pituitaries

The effect of castration on pituitary common alpha and LH-beta subunit mRNA levels was examined in adult male rats in a dot-blot hybridization assay using cytosolic mRNA and 32P labelled plasmids containing cDNA encoding sequences of the subunits. Orchidectomy increased alpha subunit mRNA levels threefold by day 4 with no further rise at 2 months. The LH-beta subunit mRNA levels increased by threefold at 2 months. Serum LH levels increased by up to fortyfold (2 months). Pituitary LH content increased by fourfold at 2 months, though was reduced at 4 days after castration. These results suggest that transcription of the alpha and LH-beta genes are similarly regulated after castration. However the greater magnitude of serum LH increase after castration than that of both LH subunit mRNA levels and the bidirectional changes in pituitary LH content implies additional translational/post-translational control of gonadotrophin biosynthesis by gonadal hormones.