Secretion of Calcitonin Gene-Related Peptide from Baby Rat Thyroid Glands in Vitro

Abstract
Thyroid glands from 8-day-old rat pups were incubated in serum-free medium for 6 hr. Both calcitonin (CT) and calcitonin gene-related peptide (CGRP) released into medium were measured by radioimmunoassay. In 6 separate experiments CGRP was easily detected in medium in ng/ml concentrations. In 4 of the 6 experiments, where CT release was stimulated by high medium [Ca], the concentration of CGRP in medium showed a positive, significant correlation with the medium CT concentration (r = 0.41=0.69, p < .05 - < .01). The results are in concert with reports describing the presence of CGRP in the C-cell, and they further show that CGRP, as well as CT, can be secreted by C-cell.