15α-hydroxytestosterone produced in vitro and in vivo in the sea lamprey, Petromyzon marinus

Prior research has shown that the testes of lampreys are able to synthesize 15-hydroxylated steroid hormones in vitro. Here we show that testes of the sea lamprey Petromyzon marinus L. are able to convert tritiated testosterone into tritiated 15alpha-hydroxytestosterone (15alpha-T) in high yield. The identity of the tritiated 15alpha-T has been confirmed by: co-elution with standard 15alpha-T on high performance liquid chromatography (HPLC); co-elution on thin layer chromatography (TLC); co-elution of acetylated tritiated and standard 15alpha-T on TLC; and strong binding to an antiserum developed against 15alpha-T. The strong reaction between the tritiated 15alpha-T and the antiserum has been used to develop a radioimmunoassay (RIA). The RIA operates over the range of 500-2 pg per tube; and can be applied directly to plasma samples. This assay has been used to demonstrate that 15alpha-T is present in blood plasma of the sea lamprey. The concentrations of 15alpha-T in captive lamprey were found to be as follows (pg/ml; mean +/- SEM, n): parasitic stage (reproductively immature), < 20, n = 7; pre-ovulatory females, 156 +/- 30, n = 8; ovulated females, 62 +/- 9, n = 5; pre-spermiating males, 275 +/- 19, n = 8; spermiating males, 216 +/- 48, n = 8. When spermiating male plasma was fractionated on HPLC, immunoreactivity was found exclusively in the expected elution position of 15alpha-T. The biological significance of this steroid has yet to be established. (C) 2003 Elsevier Science (USA). All rights reserved.