Calcitonin gene-related peptide promotes transient radiocalcium uptake into chick bone in vivo

We have examined the in vivo effects in chicks of intravenously injected chicken (c-) and rat (r-) calcitonin gene-related peptides (CGRP) on uptake into bone of a simultaneously administered 45Ca label. Both peptides caused transient (10 min) increases in 45Ca uptake into a variety of bone types. In dose-response experiments at 10 min, CGRP doses of 0.26-1.04 nmol/100 g body wt were found to give maximal responses. These were well developed in chicks fasted for 22 h but absent in those which were continuously fed. This contrasts with the hypercalcaemic effect of CGRP which is apparent in fed rather than fasted chicks.