Effect of estradiol 17-b on LH subunits and prolactin mRNAs expression in the pituitary of old female rats by Ewa Wolinska-Witort, Marek Snochowski, Alina Gajewska, Yannick Lerrant, Raymond Counis & Boguslawa Baranowska
Keywords: LH subunits mRNA expression; LH release; PRL mRNA expression; PRL release; pituitary; old rats
OBJECTIVES: The aim of the study was to examine susceptibility of the pituitary gland to estrogenic impulse in old, noncycling rats by measurement of steady state level of mRNAs encoding LH subunits a and b and mRNA for PRL.
METHODS: 22-month-old rats were ovariectomized and after one week they were subcutaneously implanted with silastic tubing filled with oil or with estradiol 17-b. Pituitary a, LHb and PRL mRNAs content and serum LH and PRL concentration was determined.
RESULTS: The effect of E2 treatment was manifested by the significant increase in the weight of the uterus and pituitary gland as well as by elevation of total pituitary RNA (109%, 60% and 78%, respectively; p<0.001). No significant changes (p>0.05) in serum LH concentration were observed, while levels of mRNAs encoding a and LH-b subunits were lowered by 54% (p<0.05) and 96% (p<0.01), respectively, in the rats subjected to E2 stimuli. No direct correlation between synthesis and release of LH in E2 treated old rats was observed. The blood PRL concentration and the pituitary level of PRL mRNA increased up to 2,000% and 1,300%, respectively (p<0.001). Spontaneous pituitary adenoma was observed in about 30% of the rats, irrespective of treatment.
CONCLUSIONS: These data show that in old rats estrogenic stimulus can effectively diminish both pituitary LH subunits mRNAs as well as stimulate pituitary PRL mRNA level indicating that the E2-dependent processes involved in the regulation of corresponding genes are still functional.