| Abstrakt: |
In mammals, glucocorticoids (GC) are inactivated by the oxidative activity of 11β-hydroxysteroid dehydrogenase (11β-HSD). To study that mechanism in the testes of Bufo arenarum, 11β-HSD activity and plasma corticosterone (B) were determined in toads from pre- (PR), post- (P), and reproductive (R) periods. Toad 11β-HSD is NAD+-dependent and strongly inhibited by glycyrrhetinic acid. Vmax is higher in the P period (1.37 vs. R: 0.13 and PR: 0.26 pmol/min-mg protein), whereas Kmax values (around 200 nM) remain constant. Plasma B concentrations (R: 178; PR: 61; P: 114 nM) are close to Km values, suggesting that, under baseline conditions, 11β-HSD could protect testes against GC action. [ABSTRACT FROM AUTHOR] |
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