Submitted to: International Symposium on Fish Endocrinology
Publication Type: Abstract Only
Publication Acceptance Date: June 8, 2004
Publication Date: September 5, 2004
Citation: Peterson, B.C., Small, B.C. 2004. Effects of cortisol on insulin-like growth factor binding proteins and mRNA expression levels of insulin-like growth factor I and growth hormone in channel catfish (Ictalurus punctatus). 5th International Symposium on Fish Endocrinology. Castellon, Spain, April 5-9, 2004, p. 143. Technical Abstract: Glucocorticoids are known to impede somatic growth in a number of vertebrate species. In order to better understand the mechanisms through which they may act in channel catfish, we examined the effects of feeding cortisol on the growth hormone (GH)/insulin-like growth factor-I (IGF-I)/IGF-binding protein (IGFBP) system. Fish (30.6 +/- 3.0 g) were fed two levels of cortisol; 1) High (dietary cortisol provided at 400 mg/kg feed once a day) 2) Low (dietary cortisol provided at 200 mg/kg feed once a day) and compared to a 3) Control (commercial feed provided once a day) group for 4 weeks. At the end of the study, the fish were weighed, bled and livers and pituitaries were excised from 15 fish per treatment. Final weights of the Control, High, and Low fish were 78.7 +/- 9.9, 35.3 +/- 0.1, and 39.9 +/- 5.7 g, respectively. A 20-kDa IGFBP was apparent in the High and Low treated fish while it was not detected in Control fish. Pituitary GH mRNA expression was not different between treatments (P > 0.05) while liver IGF-I mRNA was increased approximately 12-fold in High and Low treated fish compared to Control fish (P = 0.032). Overall, cortisol administration increased a 20-kDa IGFBP in circulation, increased mRNA levels of IGF-I in the liver, and had no effect on pituitary GH mRNA levels. These data suggest a role for cortisol in the regulation of the IGF-IGFBP-growth axis. An increase in expression levels of IGF-I suggests cortisol alone is not responsible for the observed growth inhibition.