Sites of in vivo extraction and interconversion of estrone and estradiol in the dog.

The interconversion and extraction of estrone and estradiol-17beta across and within different tissues or areas have been studied in the dog by the constant infusion technique. The results were calculated estradiol obtained from afferent and efferent blood and tissues at equilibrium. From these results it is concluded that: (1) there is no significant difference between metabolic clearance rates of estrone and estradiol, (2) blood transfer constants indicates a higher conversion of estradiol to estrone than of estrone to estradiol, (3) the transtissue interconversion favors the formation of estrone while the intratissue interconversion favors the formation of estradiol, (4) no interconversion of the two estrogens is observed in adipose tissue, (5) the extraction of estradiol entering a tissue was lower than the extraction of estradiol formed in these tissues, (6) calculation of the tissue metabolic clearance rates show that 63% of the total metabolism of estrone and estradiol, respectively, occurs in the splanchnic bed, and (7) the contribution of each tissues to the total interconversion of estrone and estradiol show that more than 90% of this interconversion occurs extrahepatically.