Abstract
In order to measure the interconversions of estrone (E1) and estradiol (E2) and their conversion to the 16α-hydroxylated estrogens, 16α-hydroxy estrone (16α-OHE1) and estriol (E3), we infused 11 female rhesus monkeys with [ 3H]E2 and [ 14C]E1 and measured radioactivity in the blood as E1, E2 and 16α-OHE1 ( n = 9) and in the urine as the glucuronides of E1, E2, 16α-OHE1, and E3 ( n = 11). The mean conversion of E1 to E2 as measured in blood (percent of infused E1 measured in blood as E2, [ρ] BB 1,2) was 29.2 ± 1.6% and as measured in the urine of the same animals, [ρ] BM 1,2, was 77.4 ± 5.9%. The mean conversion of E2 to E1, [ρ] BB 2,1 was 21.5 ± 1.0% and as measured in urine, [ρ] BM 2,1 was 67.7 ± 4.6%. Thus for both estrone and estradiol only 30–35% of the interconversions occurred in pools which were in equilibrium with the blood pool of these estrogens. The remaining 65–70% occurred in a pool, probably liver, in which glucuronidation occurred immediately after conversion. The conversion ratios (the ratio of the concentration in the blood of radioactivity as 16α-OHE1 to its precursor, CR Prec, 16α-OHEI) was 0.036 + 0.008 for CR E1, 16α-OHE1 and 0.0039 ± 0.0010 for CR E2, 16α-OHE1. The percentages of administered E1 excreted in the urine as the glucuronides of E1, E2, 16α-OHE1 and E3 were 20.1 ± 1.5, 1.6 ± 0.2, 0.96 ± 0.20 and 0.76 ± 0.07 respectively. The percentages of administered E2 excreted in the urine as E1, E2, 16α-OHE1 and E3 were 14.4 ± 1.0, 2.2 ± 0.3, 0.57 ± 0.05 and 0.68 ± 0.11 respectively. Thus there are minor differences in the patterns of excreted metabolites of E1 and E2. Furthermore, 16α-OHE1 and E3 are not major metabolites of E1 or E2 in the female rhesus monkey.
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