Metabolism of arterial plasma estrogens by the splanchnic organs of the dog in vivo

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Abstract

In order to study the splanchnic metabolism of blood-borne estrogens, a constant infusion of estrone-6,7-3H was made in a series of dogs, and arteriovenous (A-V) differences at equilibrium were determined for estrone-6,7-3H and for its products estradiol-17β, estrone sulfate, estrone glucosiduronate, and estradiol-17β glucosiduronate across the splanchnic bed (artery-hepatic vein), the small intestine (artery-superior mesenteric vein), and the spleen (artery-splenic vein). Per cent extractions (100 - [V/A] 100) were calculated. The plasma metabolic clearance rate (MCR) for estrone was measured. Principal findings were as follows: mean MCR was 731 liters/day per m2, SEM 50. By comparison with estimated hepatic plasma flow and using the observed splanchnic extraction of estrone, 45-71% of estrone metabolism was calculated to be extrasplanchnic. The significant mean per cent extractions were as follows (SEM in parentheses): splanchnic bedestrone 85.9 (1.92), estradiol-17β 88.11 (3.36), estrone sulfate 27.9 (5.22), estrone glucosiduronate -48.5 (9.33), estradiol-17β glucosiduronate -33.3 (80.3); small intestine—estrone 45.3 (2.60), estradiol-17β 46.1 (12.9), estrone glucosiduronate - 30.8 (7.9); spleen—estrone 35 (3.8), estrone glucosiduronate 12 (3.7). These results lead to the following conclusions. Both estrone and estradiol-17β are nearly completely extracted in one passage through the splanchnic bed. There is net uptake of estrone sulfate and net production of estrone glucosiduronate and of estradiol-17β glucosiduronate by the splanchnic bed. There is net uptake of estrone and of estradiol-17β by the intestine, associated with substantial net production of estrone glucosiduronate. There is net uptake of estrone by the spleen and a small but significant net uptake of estrone glucosiduronate.

Authors

Delwood C. Collins, Hugh D. Robinson, Carolyn M. Howard, John R. K. Preedy