The expression of calcitonin, calcitonin gene-related peptide and somatostatin in the thyroids of rats of different ages.

Using immunocytochemistry and in situ hybridisation expression of calcitonin, calcitonin gene-related peptide (CGRP) and somatostatin was examined in rat thyroids. The immunocytochemical reactions demonstrated the presence of the proteins under investigation at all stages of rat life. Calcitonin and CGRP produced the most numerous parafollicular cells, while somatostatin was present in a few cells only. The number of cells producing the above-mentioned hormones was found to increase in rats with the progressing of age. Hybridocytochemical techniques corroborated the results obtained using immunocytochemical techniques. The most numerous cells were found to contain mRNAs for calcitonin and CGRP. In the case of somatostatin, however, multiple parafollicular cells produced mRNA for the hormone but few cells demonstrated the presence of the corresponding protein.