Effects of cortisol on GH-IGF-I axis in the euryhaline tilapia, Oreochromis mossambicus

A single intraperitoneal injection of cortisol at doses of 10 and 50 mug/g significantly reduced plasma IGF-I levels after 24 and 48 hours. The reduction in plasma IGF-I was negatively correlated with plasma cortisol levels. No significant change was seen in plasma GH at any of the time points examined. Cortisol treatment significantly reduced IGF-I mRNA levels in the liver of up to 50 % after 48 hours. Cortisol at doses of 2 and 10 mug/g significantly increased plasma 30 and 24 kDa IGFBPs after 2, 4, 8 hours of injection without altering the plasma IGF-I levels. These effects were not seen at 24 and 48 hours. These results indicate that cortisol rapidly increases 30 and 24 kDa IGFBPs and slowly reduces plasma IGF-I levels by inhibiting hepatic IGF-I gene expression, thus exerting an inhibitory influence on somatic growth in teleosts.