The authors have studied the effects of several porcine enteric polypeptide hormones on trout calcitonin (tCT) secretion in long lived monolayer cultures of calcitonin secreting (C-) cells derived from trout ultimobranchial glands. Gastrin, pancreozymin (CCK PZ), glucagon, and secretion have dose related stimulatory effects on tCT secretion; the distinct effects of secretion on tCT secretion are in contrast to its lack of CT secretagogue activity in some mammals. Synthetic peptide hormones and/or their structural analogs have variable secretory effects which correspond in general to the potency of the analogs for the well recognized biological actions of these various peptide hormones in mammals. Although enteric peptide hormones are present in fish, their physiological role in the regulation of CT secretion has not been studied. These in vitro studies indicate a possible role for these hormones in the control of tCT secretion and support the concept that there are differences in the regulators of C cell function in higher and lower vertebrates. In vivo studies of fish CT secretion are needed to establish the physiological significance of these in vitro studies of fish C cell function.
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