Studies on in vitro effect of serotonin on calcitonin secretion by rat thyroid C cells.
Thyroid glands of young rats were incubated for 3 h in Eagle's solution supplemented with 5-hydroxy-l-tryptophan (5-HTP) or with serotonin. Following control incubations or incubations with serotonin, no serotonin could be demonstrated in C cells using immunocytochemical techniques. However, serotonin was demonstrated in the secretory granules of all C cells following incubation with 5-HTP. The secretory function of C cells was evaluated by ultrastructural and immunocytochemical studies, and by calcitonin radioimmunoassays of the incubation medium. Following incubation with 5-HTP, the secretory function of the majority of C cells was inhibited, and calcitonin levels in the media were decreased. Incubation with serotonin produced an increased secretory function of C cells and higher calcitonin levels in the media. The results indicate that serotonin and its direct precursor, 5-HTP, affect calcitonin secretion by rat thyroid C cells by distinct mechanisms.
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D006916:5-Hydroxytryptophan / Q000494:pharmacology; D001078:APUD Cells / Q000187:drug effects* / Q000378:metabolism / Q000648:ultrastructure; D000818:Animals; D002116:Calcitonin / Q000378:metabolism*; D003594:Cytoplasmic Granules / Q000378:metabolism; D006651:Histocytochemistry; D066298:In Vitro Techniques; D008297:Male; D008854:Microscopy, Electron; D051381:Rats; D012701:Serotonin / Q000494:pharmacology*; D013961:Thyroid Gland / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism
D012701:Serotonin; D002116:Calcitonin; D006916:5-Hydroxytryptophan