Mammotroph autoregulation: intracellular fate of internalized prolactin.
As part of a study concerning the mechanism of mammotroph autoregulation, the intracellular fate of [125I]iodo rat PRL, internalized by mammotrophs, was determined by quantitative electron microscope autoradiography. Simple grain density (GD) analysis of mammotroph autoradiograms showed that 5 cellular compartments (plasma membrane, Golgi apparatus, secretory granules, nucleus and mitochondria) were significantly labeled and that the labeling pattern in these compartments changed with time. Inclusion of a 25-fold excess of unlabeled PRL inhibited the binding of radiolabeled hormone to mammotrophs by approximately 85%. At no time were any grains found associated with lysosomes and there was no evidence of degradation of the radiolabeled PRL as judged by SDS-polyacrylamide gel electrophoresis or cold perchloric acid precipitation of cell extracts or media samples. Delivery of internalized PRL to a number of specific intracellular organelles suggests that these organelles may serve in the autoregulation of PRL secretion.
D000818:Animals; D001345:Autoradiography; D001665:Binding Sites; D002478:Cells, Cultured; D003594:Cytoplasmic Granules / Q000502:physiology; D005260:Female; D006706:Homeostasis; D010903:Pituitary Gland, Anterior / Q000166:cytology* / Q000378:metabolism; D011388:Prolactin / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains
D011388:Prolactin