Tissue metabolism of estrogens in the female rhesus monkey

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]E_i). 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 E_i measured in blood as product E₂ [ p]_BB^{E1, E2} (0.25 ± 0.02) than for [ p]_BB^{E1, 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 E_i, 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.