Existence of adrenodoxin‐like peptide in teleost fishes: Immunohistochemical evidence

Abstract

AbstractThis communication reports the first evidence, based on immunohistochemistry, for the presence of adrenodoxin‐like protein in poikilothermic vertebrates, two species of teleost fishes. Adrenodoxin (adrenal ferredoxin) is an iron‐sulphur protein present in the mitochondrial matrix of mammalian and avian adrenal cortex. Presence of this protein in the adrenal cortex or its equivalent (interrenal) of poikilothermic vertebrates is unknown to date. Contrary to the expectation, an earlier study using EPR spectrometry failed to demonstrate adrenodoxin in tiger shark and green turtle leading to the hypothesis that mitochondrial steroid hydroxylase systems (Type II enzymes) in poikilotherms might be similar to the microsomal counterparts (Type I enzymes) which does not involve adrenodoxin. ABC method of immunohistochemistry in the present study demonstrated that antiserum to bovine adrenodoxin reacts specifically and intensely with interrenal cells of the Asian seabass (Lates calcarifer) and the tilapia (Oreochromis mossambicus), indicating that adrenodoxin or its homologue is present in the poikilotherms also. The results further suggest the existence of a distinct electron transport system for mitochondrial steroid hydroxylation in poikilotherms as in mammals. © Wiley‐Liss, Inc.