Eel (Anguilla japonica) testis 11 beta-hydroxylase gene is expressed in interrenal tissue and its product lacks aldosterone synthesizing activity

A recombinant expression vector containing Japanese eel (Anguilla japonica) testis cytochrome P450(11 beta) (11 beta-hydroxylase) cDNA was introduced into COS-1 cells. Enzymatic activity of the expressed P450(11 beta) for cor ticosteroid synthesis was analysed by incubating transfected cells with C-1 4-labelled 11-deoxycorticosterone or H-3-labelled deoxycortisol as substrat es. Thin layer chromatography of incubation medium revealed that a high per centage of 11-deoxycorticosterone was converted into corticosterone and 11- dehydrocorticosterone but no aldosterone was detected. Similarly, deoxycort isol was converted into cortisol and cortisone. These results show that eel P450(11 beta) does not possess significant aldosterone synthesizing activi ty. Northern blot analysis detected a 1.8 kb transcript of P450(11 beta) us ing RNA extracted from interrenals of untreated Japanese eel but no hybridi zation signal was apparent using RNA extracted from brain, spleen, heart, m uscle or testis. Immunohistochemistry using an antiserum against P450(11 be ta) also revealed strong immunostaining in interrenal cells. (C) 1998 Elsev ier Science Ireland Ltd. All rights reserved.