Somatostatin acts via a pertussis toxin-sensitive mechanism on calcitonin secretion in C-cells.
The effect of the somatostatin analog octreotide on cAMP-mediated calcitonin (CT) secretion and cAMP accumulation in C-cells was investigated. Glucagon stimulated cAMP accumulation and CT secretion with a maximal effect at a concentration of 10(-6) M. The cAMP antagonist RpcAMPs blocked the glucagon-induced CT secretion down to control levels. Therefore, no other second messengers seem to be involved in glucagon-stimulated CT secretion. Octreotide in increasing doses (10(-9) to 10(-6) M) inhibited cAMP accumulation and CT secretion with a maximal effect at a concentration of 10(-7) (40% and 29% of control values, respectively). Pretreatment of the cells with 100 ng/mL pertussis toxin for 24 hours abolished the inhibitory effect of octreotide on cAMP accumulation and CT secretion (82% and 58% of control values, respectively). Similar results were obtained under the influence of the phosphodiesterase inhibitor IBMX. Therefore, we conclude that somatostatin modulates adenylate cyclase-coupled CT secretion in C-cells via a pertussis toxin-sensitive G-protein possibly in an autocrine/paracrine way.
Department of Internal Medicine I, Endocrinology and Metabolism, University of Heidelberg, Germany.
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Zink
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Scherubl
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Raue
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Ziegler
D037361:Adenylate Cyclase Toxin; D000818:Animals; D002116:Calcitonin / Q000378:metabolism*; D002277:Carcinoma / Q000378:metabolism*; D000242:Cyclic AMP / Q000378:metabolism; D005934:Glucagon / Q000494:pharmacology; D015282:Octreotide / Q000494:pharmacology; D037342:Pertussis Toxin; D051381:Rats; D013004:Somatostatin / Q000494:pharmacology* / Q000502:physiology; D013961:Thyroid Gland / Q000166:cytology* / Q000378:metabolism; D013964:Thyroid Neoplasms / Q000378:metabolism* / Q000473:pathology; D014407:Tumor Cells, Cultured / Q000378:metabolism; D010566:Virulence Factors, Bordetella / Q000494:pharmacology*
D037361:Adenylate Cyclase Toxin; D010566:Virulence Factors, Bordetella; D013004:Somatostatin; D002116:Calcitonin; D005934:Glucagon; D000242:Cyclic AMP; D037342:Pertussis Toxin; D015282:Octreotide