Identification of 5 beta-pregnane and 5 beta-androstane derivatives in adrenal venous and peripheral blood plasma of the female possum (Trichosurus vulpecula).

In the possum a marked sex difference has been found in the steroids in adrenal venous plasma. Four 5 beta-pregnane and four 5 alpha (beta) androstane derivatives together with ten 4-ene-3-keto steroids were isolated from the adrenal venous plasma of the female and definitively identified by gas chromatography-mass spectrometry. The major reduced steroids were: 5 beta-pregnane-3 alpha,17 alpha-diol-20-one and 5 beta-pregnane-3 alpha,17 alpha,20 alpha-triol, at concentrations of 52 +/- 12 micrograms/100 ml and 44 +/- 8 micrograms/100 ml mean +/- SEM respectively. The concentration of cortisol was 198 +/- 47 micrograms/100 ml. The concentration of the 2 reduced steroids in peripheral plasma were approx. 100 times less. In contrast the adrenal venous plasma of a male contained 14 steroids of which only three, found in trace amounts, were reduced. The results confirm previous in vitro observations that reduced steroids are produced by the adrenocortical special zone, which is only present in the female. The physiological significance of the presence of reduced steroids of adrenocortical origin in the circulation of the female possum is discussed.