Abstract
Pit-1, or GHF-1, is a transcription factor specific to the anterior pituitary and is involved in the expression of the GH, PRL and TSH-β-subunit genes. The expression of these genes is modulated by changes in the steroid environment. Therefore, we asked the question as to whether this effect could be mediated, at least in part, by changes in Pit-1 expression. Adult male rats were castrated and implanted subcutaneously with a Silastic capsule that was either empty or that contained testosterone (T). Intact controls were sham-operated. Four days later, animals were sacrificed and pituitaries were removed and processed for in situ hybridization to detect Pit-1 messenger RNA (mRNA). A S35 labeled fiboprobe was prepared by in vitro transcription of a 915 bp insert of the coding region of the Pit-1 cDNA. This probe was applied to 12 μm sections of the pituitaries and standard in situ hybridization methodologies were followed. Specific labeling was found only in the anterior pituitary, with the posterior and intermediate pituitaries serving as negative controls. Densitometric analysis of the tissue sections (8 per animal) was performed by using an automated image analysis system. Castrated animals had significantly lower levels of Pit-1 mRNA when compared to intact animals. Replacement with physiological levels of testosterone inhibited this decline (ANOVA: p<0.005). There was no significant difference between intact controls and castrated T-replaced animals.
Conclusion: Changes in circulating levels of sex steroids modulate the expression of Pit-1. Hence, the effects of sex steroids on the synthesis of certain anterior pituitary hormones may be mediated, at least in part, through the modulation of this specific transcription factor.
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González-Parra, S., Chowen, J., Garcia-Segura, L. et al. PIT-1 GENE EXPRESSION IN THE ANTERIOR PITUITARY IS MODULATED BY CHANGES IN CIRCULATING LEVELS OF TESTOSTERONE. Pediatr Res 33 (Suppl 5), S28 (1993). https://doi.org/10.1203/00006450-199305001-00149
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DOI: https://doi.org/10.1203/00006450-199305001-00149