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142 RECIPROCAL CHANGES IN 5α-REDUCTASE (5αR) AND 17β-OXIDOREDUCTASE (17OR, E.C.1.1.1.64) ACTIVITY IN HUMAN FORESKIN BEFORE PUBERTY

The activity of 5αR in human genital skin has been shown to be high during the first months of life and to decrease thereafter. However, no coaparable data are available on 170R which is involved in the reversible interconversion of testosterone (T) and 4-androstenedione (A), two potential substrates for 5αR. We measured these enzymes in foreskin homogenates obtained froa normal newborns and boys up to 8 yrs of age using A as a substrate in a radioenzymatic assay. Foreskin from 32 boys were first pooled in 5 age groups (1, newborns; 2, 1-6 no; 3, 6-12 mo; 4, 1-3 yrs; 5, 3-8 yrs) for the simultaneous determination of 5αR and 170R. Additional samples (n = 27) representative of the same age groups were then processed individually. The activity of 5αR is significantly higher (Kruskal-Wallis test: p = .002) in newborns than in older children. In contrast, 170R is very low at birth (41 ± 3 pmol.h−1.mg−1 protein, mean ± SEM, n = 7) and increases steadily (group 5: 279 ± 135, n = 6). Despite large interindividual variation, these values are significantly different (p = .001). The low activity of foreskin 170R in the normal infant is surprising since testicular production of T which also involves 170R activity is high during this period. This suggests a tissue-specific regulation of 170R. Moreover, maturation of this enzyme in human foreskin appears to be independent of gonadal function. Whether the reciprocal changes in 5αR and 170R in foreskin are causally related remains to be established.