Changes in LHbeta-gene and FSHbeta-gene expression in the ram pars tuberalis according to season and castration.

Luteinizing hormone beta (LHbeta) and follicle stimulating hormone beta (FSHbeta) subunits and their mRNAs were studied in the ram pars tuberalis following different seasonal (winter vs summer) and experimental (intact vs castrated animals) conditions. Hormone-containing cells were identified by immunohistochemistry, using homologous double-stranded 35S-cDNAs. The labelling was quantified by image analysis. Immunohistochemical staining showed that cells containing LHbeta and FSHbeta were localized mainly in the ventral part of the pars tuberalis but that, in the summer, additional LHbeta containing cells were present in the dorsal part in intact rams. On the other hand, LHbeta-mRNA labelling was found in the whole pars tuberalis in wethers but only in the ventral part in intact rams. The magnitude of LHbeta-mRNA labelling was significantly greater in summer than in winter rams, and in castrated than in intact animals (P<0.001). However, the number of labelled cells was found to be the greatest in the winter (P<0.001) and was not affected by castration. FSHbeta-mRNA expression was similar to that of LHbeta-mRNA except that the level and extent were considerably lower. Thus, our results show an increase in the magnitude of gonadotropin beta subunit-mRNA in the summer and following castration; this increase appears to involve the entire pars tuberalis.