Progesterone metabolism in the ovaries and testes of the echinoid Lytechinus variegatus Lamarck (Echinodermata)

In the present study we examined the metabolic fate of progesterone (P4) in homogenate and tissue minces of the ovaries and testes of Lytechinus variegatus. P4 was metabolized primarily into 5α-reduced metabolites including, 5α-pregnane-3,20-dione (DHP), 3β-hydroxy-5α-pregnan-20-one (3β,20-one), 5α-pregnane-3β,20α-diol (3β,20α-diol), 5α-pregnane-3β,20β-diol (3β,20β-diol), and 5α-pregnane-3α,20α-diol (3α,20α-diol) by both the ovaries and testes. The capacity to metabolize P4 did not differ between the ovaries and testes. However, the relative quantity of 5α-pregnane-3β,20ξ-diol synthesized from ovary and testis tissue minces was about 3.3-fold higher than from homogenate preparations. Differences in the synthesis of 3β,20-one and 3α,20α-diol in both ovary and testis minces were dependent on reproductive state. This study demonstrates the pathway of P4 conversion in the ovaries and testes of L. variegatus and indicates the rapid conversion of P4 into 5α-reduced metabolites in these tissues. Although P4 metabolism is not sex specific, sex-specific responses to P4 metabolites have been demonstrated previously. We hypothesize that the sex-specific responses of the ovaries and the testes to P4 may be associated with receptor-level regulatory processes.