Document Detail

Characterization of functional receptors for somatostatin in rat pituitary cells in culture.
MedLine Citation:
PMID:  210185     Owner:  NLM     Status:  MEDLINE    
GH4C1 cells are a clonal strain of rat pituitary tumor cells which synthesize and secrete prolactin and growth hormone. Somatostatin, a hypothalamic tetradecapeptide, inhibits the release of growth hormone and, under certain circumstances, also prolactin from normal pituitary cells. We have prepared [125I-Tyr1]somatostatin (approximately 2200 C1/mmol) and have shown that this ligand binds to a limited number of high affinity sites on GH4C1 cells. Half-maximal binding of somatostatin occurred at a concentration of 6 x 10(-10) M. A maximum of 0.11 pmol of [125I-Tyr1]somatostatin was bound per mg of cell protein, equivalent to 13,000 receptor sites per cell. The rate constant for binding (kon) was 8 x 10(7) M(-1) min(-1). The rate constant for dissociation (koff) was determined by direct measurement to be 0.02 min(-1) both in the presence and absence of excess nonradioactive somatostatin. Binding of [125I-Tyr1]somatostatin was not inhibited by 10(-7) M thyrotropin-releasing hormones. Substance P, neurotensin, luteinizing hormone-releasing hormone, calcitonin, adrenocorticotropin, or insulin. Of seven nonpituitary cell lines tested, none had specific receptors for somatostatin. Somatostatin was shown to inhibit prolactin and growth hormone production by CH4C1 cells. The dose-response characteristics for binding and the biological actions of somatostatin were essentially coincident. Furthermore, among several clonal pituitary cell strains tested, only those which had receptors for somatostatin showed a biological response to the hormone. We conclude that the characterized somatostatin receptor is necessary for the biological actions of somatostatin on GH4C1 cells.
A Schonbrunn; H Tashjian
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Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  The Journal of biological chemistry     Volume:  253     ISSN:  0021-9258     ISO Abbreviation:  J. Biol. Chem.     Publication Date:  1978 Sep 
Date Detail:
Created Date:  1978-10-27     Completed Date:  1978-10-27     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  2985121R     Medline TA:  J Biol Chem     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  6473-83     Citation Subset:  IM    
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MeSH Terms
Clone Cells
Growth Hormone / secretion
Pituitary Gland / metabolism*
Pituitary Neoplasms / metabolism
Prolactin / secretion
Receptors, Cell Surface / metabolism*
Somatostatin / metabolism*,  pharmacology
Reg. No./Substance:
0/Receptors, Cell Surface; 51110-01-1/Somatostatin; 9002-62-4/Prolactin; 9002-72-6/Growth Hormone

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