Measurement of secretogranin II release from individual adenohypophysial gonadotropes.
Secretogranin II (SG-II) is an acidic 86-kDa protein found in high abundance in the anterior pituitary gland. In the present studies, we investigated the secretion and the localization of SG-II using pituitary cells from female rats at all stages of the estrous cycle. Double immunofluorescence staining revealed that SG-II immunoreactivity was localized in low abundance in about half of all pituitary cells and in high abundance in all of the luteinizing hormone (LH)-immunoreactive cells (which represent approximately 5% of all pituitary cells). Using a reverse hemolytic plaque assay for measurement of SG-II release from individual pituitary cells in culture, we found that SG-II secretion was strongly stimulated by gonadotropin-releasing hormone in a dose-related fashion, and the amount of SG-II secretion was also related to the stage of the estrous cycle: it was highest at proestrus and lowest at estrus. SG-II plaque assay followed by LH immunofluorescence staining further revealed that all the SG-II-secreting cells contained LH immunoreactivity. At proestrus all the LH-immunoreactive cells secreted SG-II, whereas another days of the estrous cycle only a fraction of them did so. Thus our findings demonstrate a striking resemblance between SG-II and LH with regard to cell localization and secretory regulation.
Wei
N
N
Department of Physiology and Biophysics, University of Alabama at Birmingham 35294.
Kakar
S S
SS
Neill
J D
JD
D000818:Animals; D002864:Chromogranins; D004971:Estrus; D005260:Female; D005455:Fluorescent Antibody Technique; D006462:Hemolytic Plaque Technique; D007106:Immune Sera; D007986:Luteinizing Hormone / Q000378:metabolism*; D010903:Pituitary Gland, Anterior / Q000166:cytology / Q000378:metabolism*; D011506:Proteins / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013194:Staining and Labeling; D014018:Tissue Distribution
D002864:Chromogranins; D007106:Immune Sera; D011506:Proteins; D007986:Luteinizing Hormone