Hydrolysis of estrogen conjugates by the lungs of the dog in vivo.

Although hydrolysis of certain estrogen conjugates released into the systemic circulation is now known to occur in the human and in the dog, the site or sites of such hydrolysis remained unidentified. In an attempt to identify such sites, radioactive estrone was infused intravenously into a series of male dogs and serial paired samples of blood were obtained from the right ventricle (RV) and a peripheral artery (A). The samples were analysed for total radioactivity, unconjugated radioactive estrogens, radioactive estrone, estradiol-17beta, estrone sulfate, estrone glucosiduronate and estradiol-17beta glucosiduronate(s). The mean percent extraction across the lungs (see article) was calculated for each radioactive moiety analyzed. There was no significant percent extration of total radioactivity or of estrone sulfate. The mean percent extractions for unconjugated estrogens and for estrone and estradiol-17beta were -24.7, -21 and -34.3 respectively (P less than 0.01), indicating net production by the lungs. The mean percent extractions for estrone glucosiduronate and estradiol-17beta glucosiduronate(s) were +19.8 and +10.0 respectively (P less then 0.01), indicating net uptake of these conjugates by the lungs. Statistical analysis showed that the two processes were related. Our findings support the hypothesis that the lungs are one site, possibly the main site, at which hydrolysis of estrogen glucosiduronates occurs in the dog.