Nongenomic action of cortisol in rainbow trout hepatocytes

Abstract

Cortisol rapidly activates cell signalling in trout hepatocytes; however, the mechanisms are far from clear. We tested the hypothesis that rapid action of cortisol involves modulation of intracellular Ca2+ levels in trout hepatocytes. Stress level of cortisol reported in fish plasma elicits a rapid increase in intracellular Ca2+ level as determined by Fura‐2AM ratiometric imaging. The increase in intracellular Ca2+ level in trout hepatocytes was also seen with the membrane impermeable form of the steroid (cortisol‐BSA), and this response was not affected by mifepristone (glucocorticoid receptor antagonist). We determined the role of extracellular and intracellular stores of calcium in affecting cortisol‐induced elevation in Ca2+ levels by using EGTA (a chelator) and BAPTA‐AM (inhibitor), respectively. Furthermore, we determined if IP3R pathway was involved in the activation of intracellular stores by using various inhibitors, including PLC inhibitor (U73122), thapsigargin (SERCA blocker) and Rynodine (RyR blocker). Also, L‐type calcium channel blocker Nifedipine and Ca2+release‐activated Ca2+ (CRAC) channel blocker Cpd5J‐4 were utilized to determine the mode of entry of extracellular calcium in response to cortisol stimulation. Overall, our results suggest that cortisol rapidly increases intracellular calcium levels and this may be mediated by the activation of CRAC channel in trout hepatocytes.Support or Funding InformationThis study was supported by the Natural Sciences and Engineering Research Council of Canada Discovery Grant to MMV.