THE CALCITONIN-GENE IS EXPRESSED IN SALMON GILLS

Calcitonin is an important physiological regulator of salmon gills. Al though the calcitonin receptor was found in salmon gills, the critical question concerning the source of the hormone remained unanswered. In this communication, evidence is presented for expression of calcitoni n mRNA and its encoded peptide in gills of the pink salmon, Oncorhynch us gorbuscha. The expression of calcitonin gene transcripts was demons trated by reverse transcription-polymerase chain reaction, Southern hy bridization, and sequencing. The sequencing identified a sequence corr esponding to that of exon 4 of the salmon calcitonin gene. Expression of the encoded calcitonin gene in gills was detected by radioimmunoass ay in gill extracts. This synthesis of calcitonin in gills, which also possess specific receptors to the peptide, suggests function of an au tocrine or paracrine process producing calcitonin in this tissue. Thes e observations confirm and extend previous reports on the physiologica l role of calcitonin in fish gills.