HYBRIDOCYTOCHEMICAL AND IMMUNO-ULTRASTRUCTURAL STUDY OF CALCITONIN-GENE EXPRESSION IN CULTURED MEDULLARY CARCINOMA-CELLS

The study was aimed at a morphological demonstration of calcitonin (CT ) gene expression in cultured TT cells, or, more specifically, hybrido cytochemical detection of CT mRNA and calcitonin gene-related peptide (CGRP) mRNA and ultrastructural localization of the two hormones. The TT cells originated from medullary carcinoma of human thyroid gland. U ltrastructural studies of TT cells demonstrated a well-developed rough endoplasmic reticulum, large Golgi apparatus and low number of secret ory granules. Hybridocytochemical studies showed the presence of mRNAs for CT and CGRP in all TT cells. At the ultrastructural level, double immunolabelling demonstrated that the two hormones were always expres sed together in the same secretory granules. Our results provide a sig nificant addition to the biochemical studies performed up to now and i ndicate that all TT cells produce both mRNAs and both hormones in para llel.