EFFECTS OF STANNIUS CORPUSCLE EXTRACTS AND 17-BETA-ESTRADIOL ON THE CONCENTRATION OF GALLBLADDER BILE CALCIUM IN THE RAINBOW-TROUT, ONCORHYNCHUS-MYKISS

To examine a role of calcium excretion into gallbladder bile in calciu m homeostasis, a single administration of Stannius corpuscle extracts from rainbow trout or 17beta-estradiol was given the rainbow trout, On corhynchus mykiss, and serum and bile calcium concentrations were anal ysed by flame photometry. Calcium concentrations were approximately 3. 7 times higher in bile than serum in the control fish. Calcium-roaded fish showed marked increases in serum and bile calcium conentrations. The simultaneous administration of the extracts effectively reduced th e hypercalcemia after 3 h. However, the extracts did not have any effe cts on bile calcium concentrations at any examination times. 17beta-es tradiol induced marked hypercalcemia with a peak 10 days after adminis tration. In contrast, bile calcium concentrations decreased to a minim um level on the day showing a mirror profile to changes in serum calci um concentrations (r = -0.95). These results indicate that gallbladder bile calcium is not involved in the hypocalcemic regulation by Stanni us corpuscle extracts, but decreases in concentration as a result of v itellogenin synthesis in hepatocytes.