title: Regulation of secretory granule formation in chronically hypersecretory melanotrophs in the rat pituitary.
abstract: The formation of secretory granules in chronically hypersecretory melanotrophs in the rat pituitary was studied. Hypersecretion was induced by treatment with the dopamine antagonist haloperidol (1.5 mg/kg daily for 7 days), which releases the normal neural dopaminergic inhibition of secretion from the melanotroph. Morphometric analysis showed a 100% increase in the volume fraction of granular endoplasmic reticulum after haloperidol treatment, while the volume fractions of electron-dense granules, electron-lucent granules and the Golgi apparatus were unaltered. The mean diameter of the mature secretory granules was increased by 10%, indicating a 30% increase in mean granule volume. A similar increase in diameter was observed in condensing granules within the Golgi area. With earlier results on the effect of chronic inhibition the study shows that a main adaptive response of the melanotroph to altered secretory conditions is a change in the volume of the secretory granules, regulated by a mechanism that operates at an early stage of granule formation.
authors.affiliation: Department of Anatomy, University of Helsinki, Finland.
authors.forename: N
authors.initials: N
authors.lastname: Bäck
authors.forename: S
authors.initials: S
authors.lastname: Soinila
mesh_terms: D000818:Animals; D001971:Bromocriptine / Q000494:pharmacology; D003594:Cytoplasmic Granules / Q000187:drug effects / Q000648:ultrastructure*; D004721:Endoplasmic Reticulum / Q000187:drug effects / Q000648:ultrastructure; D006056:Golgi Apparatus / Q000187:drug effects / Q000648:ultrastructure; D006220:Haloperidol / Q000494:pharmacology; D008297:Male; D008854:Microscopy, Electron; D010902:Pituitary Gland / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure*; D010907:Pituitary Hormones / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D010907:Pituitary Hormones; D001971:Bromocriptine; D006220:Haloperidol