CALCITONIN MESSENGER-RNA IS PRODUCED IN LIVER BY 2 DIFFERENT SPLICINGPATHWAYS

Calcitonin, the hypocalcemic hypophosphatemic hormone is produced in t he thyroid by the C-cells. We recently detected the presence of calcit onin and its messenger in hepatic tissue in vivo and in vitro. The cal citonin precursor is composed of the N-terminal peptide, calcitonin an d a carboxyterminal peptide. We previously reported that in normal hum an thyroid and in medullary thyroid carcinoma a second calcitonin mess enger is expressed in low quantities. This mRNA differs in its 3' regi on from the first one. It also codes for the N-terminal peptide, calci tonin and a carboxyterminal peptide which differs by the last eight am ino acids from the first. We report here that both calcitonin mRNAs ar e expressed in normal or tumoral liver. Direct estimation, by a specif ic immunoassay, of the levels of carboxyterminal peptide II, the speci fic peptide coded for by calcitonin mRNA II, confirmed that this pepti de is synthesized in human liver. (C) 1997 Elsevier Science Ireland Lt d.