Effects of the three neuropeptides, vasoactive intestinal peptide, substance P, and calcitonin gene related peptide on basal and stimulated calcitonin release in the rat.
Calcitonin is secreted from the thyroidal C-cells. Except that calcitonin secretion is stimulated by calcium, little is known of its regulation. Vasoactive intestinal peptide (VIP), substance P, and calcitonin gene related peptide (CGRP) have recently been detected within intrathyroidal neurons, and CGRP also within the C-cells, and may therefore affect calcitonin secretion. In this study, we investigated whether VIP, substance P or CGRP could influence calcitonin secretion in the rat. Each of these peptides was administered as a single injection (1.5 nmol/animal) or as a 30-min infusion (1.5 nmol/animal per 30 min) during which calcium chloride, 456 mumol/animal, was injected iv. We found that the peptides had no effect on basal calcitonin secretion, but that VIP potentiated the calcium-induced calcitonin release. Thus, the peak plasma calcitonin level following calcium chloride injection was doubled by the infusion of VIP (P less than 0.001). In contrast, neither substance P nor CGRP significantly influenced the calcium-induced calcitonin release. We conclude that VIP, a neuropeptide within intrathyroidal nerves, has the capacity to augment calcium-induced calcitonin secretion in the rat and we therefore suggest that VIP is a regulator of calcitonin secretion.
D000818:Animals; D002116:Calcitonin / Q000097:blood / Q000378:metabolism*; D015740:Calcitonin Gene-Related Peptide; D002118:Calcium / Q000097:blood; D002122:Calcium Chloride / Q000494:pharmacology; D008297:Male; D009412:Nerve Fibers / Q000187:drug effects; D009479:Neuropeptides / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D013373:Substance P / Q000494:pharmacology*; D013961:Thyroid Gland / Q000378:metabolism*; D014660:Vasoactive Intestinal Peptide / Q000494:pharmacology*
D009479:Neuropeptides; D013373:Substance P; D014660:Vasoactive Intestinal Peptide; D002116:Calcitonin; D015740:Calcitonin Gene-Related Peptide; D002122:Calcium Chloride; D002118:Calcium