Development of Prolactin and Growth Hormone Production in the Fetal Rat Pituitary: An Immunochemical Study: (hormone production/ontogeny/fetal rat pituitary/immunochemistry).

Abstract

Western immunoblot analysis was performed to monitor contents of prolactin (PRL), growth hormone (GH) and Pit-1, a transcription factor required for both GH and PRL gene expression, in developing fetal rat pituitaries. Both PRL and GH were first detected in pituitary extracts at 18 days of fetal age and their contents increased during the rest of the fetal period. Pit-1 was detectable from 16 days on. Quantitative densitometry scanning analysis of Western immunoblots showed that the PRL and GH contents were less than 10 ng per pituitary at 18 days. The PRL content increased to about 19 ng at 21 days (the last day of gestation), whereas the GH content showed much larger increase in the same period to reach about 1.2 μg per pituitary. In primary culture, dispersed pituitary cells from 19 day-old fetuses incorporated [35 S]-amino acids into immunoprecipitable GH. The incorporation into PRL was detectable after stimulation with 1 nM 17β-estradiol. These results suggests that the rat pituitary starts to produce both PRL and GH at around 18 days of fetal age.