Immunological studies on teleocalcin and salmon corpuscles of Stannius

This report describes the characterization of an antiserum to salmon teleocalcin, a glycoprotein hormone that has recently been isolated from sockeye salmon, Oncorhynchus nerka, corpuscles of Stannius (CS). Immunodiffusion studies showed that teleocalcin was immunologically identical in four species of Pacific salmon. Histological staining of adjacent sections of sockeye salmon CS by periodic acid-Schiff reagent and immunocytochemistry revealed that the teleocalcin-immunoreactive cells were also periodic acid-Schiff positive. In bioassays using rainbow trout (Salmo gairdneri), the biological effects of teleocalcin were completely abolished by pretreatment with the antiserum before injection. The antiserum was ineffective by itself, however, in neutralizing endogenous teleocalcin. Immunoprecipitation studies of in vitro translation products from salmon CS poly(A)+ RNA identified a 26K protein, which corresponds to the size of the teleocalcin monomer as predicted by cDNA sequencing studies. Similar banding patterns were obtained with purified teleocalcin and crude CS extracts by Western blot analysis. However, there was one extra band (32K) in the CS extracts that was not present in the purified hormone preparations. This may represent the pro-form of the hormone in salmon.