EXISTENCE OF ADRENODOXIN-LIKE PEPTIDE IN TELEOST FISHES - IMMUNOHISTOCHEMICAL EVIDENCE

This communication reports the first evidence, based on immunohistoche mistry, for the presence of adrenodoxin-like protein in poikilothermic vertebrates, two species of teleost fishes. Adrenodoxin (adrenal ferr edoxin) is an iron-sulphur protein present in the mitochondrial matrix of mammalian and avian adrenal cortex. Presence of this protein in th e adrenal cortex or its equivalent (interrenal) of poikilothermic vert ebrates is unknown to date. Contrary to the expectation, an earlier st udy using EPR spectrometry failed to demonstrate adrenodoxin in tiger shark and green turtle leading to the hypothesis that mitochondrial st eroid 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 presen t study demonstrated that antiserum to bovine adrenodoxin reacts speci fically and intensely with interrenal cells of the Asian seabass (Late s calcarifer) and the tilapia (Oreochromis mossambicus), indicating th at adrenodoxin or its homologue is present in the poikilotherms also. The results further suggest the existence of a distinct electron trans port system for mitochondrial steroid hydroxylation in poikilotherms a s in mammals. (C) 1994 Wiley-Liss, Inc.