Effects of N-terminal peptide of salmon proopiocortin on interrenal function of the rainbow trout

Abstract

Effects of N-terminal peptide of salmon proopiocortin (salmon NPP-I) on cortisol secretion was examined in vitro using diced interrenal tissue from the rainbow trout, Salmo gairdneri. ACTH(1–24) at concentrations of 1 to 50 n M stimulated cortisol secretion in dosedependent manner, whereas salmon NPP-I had no effect over a range of 50 p M to 500 n M. Cortisol secretion in response to various doses of ACTH(1–24) was modified slightly when 1 to 100 n M of salmon NPP-I was added to the incubation medium together with ACTH. an augmentation of in vitro secretion of cortisol in response to ACTH(1–24) was observed when the interrenal was removed from the trout pretreated with one IU of porcine ACTH but not with 10 μg of salmon NPP-I. A slight but significant potentiating effect of salmon NPP-I (10 or 100 n M) on the ACTH-induced cortisol secretion was observed when the trout was sensitized to ACTH by porcine ACTH pretreatment. Furthermore, six daily injections of salmon NPP-I into the trout induced hyperplasia of interrenal tissue. These findings suggest that NPP-I, together with ACTH, may be involved in controlling interrenal function in the trout. Such activities could be due to conservative region in the N-terminal portion of NPP.