THYROTROPIN-RELEASING-HORMONE GENE-EXPRESSION IN CULTURED ANTERIOR-PITUITARY-CELLS - ROLE OF GENDER

The present studies were undertaken to investigate the effect of gende r on thyrotropin-releasing hormone (TRH) gene expression in cultured a nterior pituitary (AP) cells. AP cells derived from 15-day-old male, f emale, or female pups that had been neonatally treated with testostero ne propionate (TP), were cultured for up to 18 days in a modified DMEM /L-15 medium containing 10% fetal calf serum. TRH and AP hormones incl uding GH, prolactin (PRL), luteinizing hormone (LH) and thyrotropin (T SH) were measured by RIA, proTRH mRNA was determined by in situ hybrid ization using a full-length riboprobe followed by quantification with a computer-assisted image analysis system. Cultures derived from femal e rats contained significantly (p < 0.01) higher amounts of TRH and se creted approximately twice (p < 0.01) as much TRH under basal conditio ns and in response to activators of the protein kinase A and C pathway s, respectively. In situ hybridization studies revealed that 'female' cultures contained significantly higher amounts of proTRH mRNA compare d to 'male' cultures. Computer-assisted image analysis demonstrated th at proTRH mRNA levels were 3.5 times higher in 'female' compared to 'm ale' cultures (p < 0.01), an effect that was the result of a significa ntly higher number (3 times; p < 0.01) of cells expressing proTRH mRNA in 'female' cultures. Neonatal TP treatment did not affect either pro TRH mRNA or TRH peptide levels. In vitro testosterone treatment result ed in a moderate rise (p < 0.05) of intracellular TRH accumulation in cultures from both sexes, however, proTRH mRNA levels remained unchang ed. Gender-specific differences were also found in the contents of all AP hormones measured: GH and TSH were significantly higher in 'male' cultures, while 'female' cultures contained larger amounts of LH and P RL. The results show that gender determines the level of TRH gene expr ession in cultured AP cells. Neonatal androgen exposure does not appea r to be a determinant in the sex-specific differences observed.