Steroid metabolism in Antarctic soft corals

Abstract

Whole body tissue preparations of the Antarctic soft corals Alcyonium paessleri and Clavularia frankliniana were incubated in vitro with the radiolabelled precursors ³H-progesterone and ³H-androstenedione to determine steroidogenic capacity. Steroidal metabolites were identified using TLC, derivitization, and recrystallization techniques. The Antarctic soft corals converted labelled precursors (³H-progesterone and ³H-androstenedione) into a maximum of five metabolites, potentially indicating the activity of the following enzymes: 5α-reductase, 3β-hydroxysteroid dehydrogenase (HSD), 17β-HSD, and acyl transferase. Both species exhibited similar steroidogenic capacity. Radioimmunoassays verified the presence of relevant concentrations of progesterone, androstenedione, testosterone, and estradiol in whole body extracts from each species of soft coral. Alcyonium paessleri and Clavularia frankliniana actively converted precursors at temperatures up to 10°C above the ambient encountered by these species. Although similar steroidal compounds are produced in other phyla of benthic invertebrates, conversion rates for these soft corals are substantially lower. The role of these steroids is as yet unidentified; however they may be related to reproduction, and be important in chemical signaling or as defensive metabolites, or they may serve as transient intermediates to the production of other bioactive derivatives.