Stimulation of calcitonin secretion by beta-calcitonin gene related peptide in rats

The presence of calcitonin gene-related peptide (CGRP) in both C-cells and nerve fibres around the thyroid blood vessels and follicles suggests that it may play a dual role, one of which may be in hormone secretion. Beta-CGRP injected intracerebroventricularly (icv) (1.875 nmol) caused a significant increase in the calcitonin CT) content of the C-cells in rat thyroid glands. The calcitonin content of the thyroids was determined by a radioimmunoassay using two antibodies and the results were expressed as ng CT/mg of fetal tissue. A significant rise in CT content of the thyroids occurred (5.5 +/- 0.5 n = 6), compared with the controls (3.5 +/- 0.1 n = 6). It is presumed that this change reflects an increase in the rate of secretion of CT in the thyroid glands of those rats so treated. The peptide might act on the central nervous system to stimulate the catecholamine outflow from the thyroid nerves and thereby increase the secretion rate of CT.