In vivo studies on the metabolism of estrone and estradiol-17beta by the brain |
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Authors: | N Kazama C Longcope |
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Institution: | Worcester Foundation for Experimental Biology Shrewsbury, Mass. 01545 USA |
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Abstract: | 3H-Estrone and H-estradiol-17β were infused in separate experiments into the jugular veins of each of 4 ewes. During the infusions blood samples were obtained from the ipsilateral jugular vein and common carotid artery. The blood samples were analyzed for radioactivity as free estrone and estradiol-17β and the conversion of infused precursor to product steroid by brain tissue, the transtissue conversion (ρPRE-PROAV) and the extraction by brain tissue of infused precursor, the transtissue extraction (1-ρPRE-PREAV) and the metabolic clearance rates were calculated.The mean ± SE for ρAV1,2 (precursor, estrone = 1; product, estradiol = 2) was 0.09 ±0.03 and the mean ± SE for ρAV2,1 (precursor, estradiol = 2; product, estrone = 1) was 0.08 ±0.02. The mean trans-tissue extraction of estrone was 0.13 ± 0.02 and of estradiol-17β was 0.14- ± 0.02. The transtissue extractions of estrone and estradiol-17β were greater than ρAV1,2 ρAV2,1 respectively in 2 of the 4 ewes.Brain metabolism of estrogens can account for only 2–4% of the total metabolism of these free estrogens from the blood pool. |
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