Tissue Metabolism of Estrogens in the Female Rhesus Monkey*

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Abstract
The overall MCRs and [p]BB values (fraction of infused precursor measured in blood as product) and individual tissue extractions and conversions were measured in the follicular and luteal phases of normal cycling female rhesus monkeys using constant infusions of [3H]estradiol ([3H]E2) and [14C]estrone ([14C]Ei). During the infusions, blood samples were obtained from the femoral artery and veins draining the splanchnic tissue, kidney, head, arm, and uterus. The overall mean (±SE) MCR for E2 (214 ± 17 liters/day) was significantly less than the MCR for E1 (295 ± 13 liters/day). There were no differences in the MCR measured in the follicular or luteal phases of the cycle. The [P]BB values were greater for the fraction of infused Ei measured in blood as product E2 [p]BBE1,E2 (0.25 ± 0.02) than for [p]BBE1,E2 (0–11 ± 0.01) Neither value was affected by the time of the cycle. The extractions (that fraction of steroid measured in arterial blood entering a tissue which is metabolized and not measured as that steroid in venous blood draining the tissue) across the splanchnic tissues were the largest of the tissue extractions measured (0.63 ± 0.05 for E2 and 0.73 ± 0.10 for estrone). The arm, uterus, kidney, and head had lower extractions, and the extraction of E2 was always lower than that of Ei, probably due to the specific globulin binding of E2. Interconversion of the estrogens occurred across each tissue bed but reflected, in general, only a small portion of the total extraction, especially for the splanchnic tissue. There was no apparent difference in any of the transtissue conversions measured in the follicular as compared to the luteal phase. The administration of pharmacological amounts of dexamethasone to three monkeys resulted in a marked increase in the MCR of estradiol and a slight decrease in the MCR of estrone. Individual tissue extractions and transtissue conversions showed no consistent alteration after dexamethasone.