Human Fetal Pituitary in Culture: Hormone Secretion and Response to Somatostatin, Luteinizing Hormone Releasing Factor, Thyrotropin Releasing Factor and Dibutyryl Cyclic AMP

Abstract

Human fetal pituitaries, 10 to 19 weeks gestation, were kept in organ or monolayer culture for up to 6 weeks. Light and electron microscopic investigation provided evidence that the morphology of the tissue was well maintained and that at least four epithelial cell types could be distinguished based on their secretory granule population. The levels of GH, LH, FSH, TSH, and PRL released into the media were determined by radioimmunoassay as a function of time in culture and gestational age. In general, the older the fetal pituitary the greater the trophic hormone secretion and the longer the release was sustained in vitro. The exception was TSH which reached undetectable levels within two weeks after initiation of the cultures regardless of the age of the fetus. Corticotrophic activity was detectable by bioassay from 11 weeks gestation. From 10 to 13 weeks gestation on, somatostatin (2 × 10⁻⁵ to 10⁻9M) inhibited GH secretion 14 to 78%, luteinizing hormone releasing factor (10⁻⁶ to 10⁻⁸M) stimulated LH and FSH secretion 2 to 4-fold and thyrotropin releasing factor (10⁻⁸M) increased TSH release 2 to 5-fold. DBcAMP (1 IDM) enhanced GH secretion at 13 weeks gestation and LH, FSH and PRL release by 15 weeks. The data suggest that the early gestation human fetal pituitary is capable of synthesizing, storing and secreting trophic hormones and that by 10 to 13 weeks gestation the gland is responsive to hypothalamic releasing and inhibitory factors as well.