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
