In vivo and in vitro conjugation and metabolism of estrogens by the baboon kidney

Labeled estrogen was injected into one of the renal arteries of baboons and urine was collected separately from each ureter via ureterostomy at various time intervals over a period of 7 h; the urinary metabolites were analyzed by DEAE-Sephadex chromatography and enzyme hydrolyses. Identification of the aglycones was made by TLC and co-crystallization upon admixture with authentic compounds. When [3H]estradiol-17beta (E2) was injected into one of the renal arteries, the major metabolites were [3H]E2-3-glucosiduronate (E2-3G) and [3H]estrone-3-glucosiduronate (E1-3G); [3H]E2-3G was excreted predominantly into the urine from the injected side during the initial 30 min after injection. Formation of [3H]E1-3G was not detectable for the first 5 min in the urine from either side. However, its excretion gradually increased and the amount was almost equal from both sides in the later hours of collection. Injection of [3H]E1 revealed ready conjugation (as E1-3G) by the kidney without significant reduction at position-17. When E2-3G, labeled with 3H at positions 6,7 and with 14C in the glucuronic moiety, was injected, it was quickly excreted in the urine of the injected side. The ratio of 3H/14C of E2-3G excreted in the urine was the same as that of the injected E2-3G. In the later periods, E1-3G, which had a slightly increased 3H/14C ratio, appeared in the urine. These results indicate that E2 and E1 are conjugated directly in the kidney to form the 3G which is excreted into the urine and that effective dehydrogenation or reduction of the steroids in vivo does not take place in the kidney. The results also show that conjugated E2 (E2-3G) is quickly excreted by the kidney of the baboon without any change in its form and that the E2-3G is dehydrogenated to E1-3G during its general circulation without significant prior removal of the glucuronic moiety. When [3H]estriol (E3) was injected, facile glucuronidation to E3-16G by the kidney was shown. Injection of an equimolar mixture of [14C]E3 and [3H]E2 showed rapid excretion of [14C]E3-16G as opposed to the slower excretion of [3H]E2-3G. These results suggested that the active sites of these conjugating enzyme systems in the kidney may be different.

Studies of phenolic steroids in human subjects. XIX. Renal conjugation of 15alpha-hydroxyestradiol-3-sulfate

In order to elucidate further the role of the kidney in the conjugation and excretion of 15alpha-hydroxy-estrogens, we synthesized doubly and singly labeled 15alpha-hydroxyestradiol-3-sulfate (15alpha-OHE-S) and determined its urinary excretory pattern after administering differently labeled 15alpha-OHE2-S into the renal artery and concomitantly into a peripheral vein and by the infusion of doubly labeled 3H-15alpha-OHE2-S-35S into the renal artery. The excretion of radioactivity in the early urinary samples and the conjugate pattern in these urines were determined. About twice as much radioactivity was excreted in the early urine samples originating from the renal artery injection than from samples obtained following peripheral administration, indicating renal conjugation and excretion of the 15alpha-OHE2-S. The latter was preponderantly excreted as the S-NAG with only a small part (about 10%) of the administered sulfate being hydrolyzed to the aglycone. The latter was then either conjugated with N-acetylglucosamine (NAG) or glucuronide, probably also in the kidney. Most of the 15-alpha-OHE2-S could not be accounted for, possibly because of biliary excretion and enterohepatic circulation. The results obtained and those already published indicate that the human kidney is capable of conjugating 15alpha-OHE2, its NAG, and its sulfate conjugates.

The metabolic fate of chlormadinone acetate in the baboon

The metabolic fate of chlormadinone acetate (17alpha-acetoxy-6-chloro-4, 6-pregnadiene-3, 20-dione; CAP) was studied in intact and biliary fistula baboons. The steroid was labeled with 3H at position 1 and with 14C at the carboxyl moiety of the 17alpha-acetate, thus affording the opportunity to ascertain the loss of the 17alpha-acetoxy group and the fate of both labels. The averages of the radioactivity excreted, given as percentages of the amounts injected, and the standard deviations were as follows: In the urine of intact animals after 6 hours, 5.7 +/- 0.2% and 5.5 +/- 0.7% of the 3H and 14C were recovered, respectively. After 6 days, there was 17.5% of the 3H and 16.2% of the 14C in the urine plus 15.3% of the 3H and 16.4% of the 14C in the feces. In baboons with biliary fistulas, the total radioactivity excreted was 7.8 +/- 0.7% of the 3H and 11.6% of the 14C in the urine, and 30.9 +/- 4.4% of the 3H and 30.7% of the 14C in the bile after 6 hours. Glucosiduronates were the predominant conjugates in the urine and bile. The similarity in the urinary excretion of radioactivity in the first 6 hours in intact and biliary fistula animals, the relatively low excretion of radioactivity in the bile and after 6 days in the urine, and the low fecal excretion suggest that the metabolites of CAP are not involved in an extensive enterohepatic circulation in the baboon. Deacetylation of the 17alpha-acetate in CAP was detected in the early collection periods of the urine and bile and constituted a very small percentage of the injected compound. No significant oxygenation of CAP at position 1 was detected. The metabolism of CAP is discussed and compared to our previously reported data on the metabolism of progesterone, ethynodiol diacetate and medroxyprogesterone acetate and the data on other progestogens reported in the literature. It appears that the excretion of CAP is significantly slower in the baboon than that of the other progestogens. The amounts of glucosiduronates of CAP and/or its metabolites formed in vivo are less than those formed with the other progestogens. Also, the extent of deacetylation of the 17alpha-acetate of CAP is much less than that of the 3beta-acetate of ethynodiol diacetate.

Metabolic fate of ethynodiol diacetate in the baboon

The enterohepatic circulation and metabolism of ethynodiol diacetate (3beta,17beta-diacetoxy-17alpha-ethynyl-estr-4-ene) in baboons were studied following the intravenous injection of this contraceptive steroid labeled with 14C (4-position) and with 3H (in either the 3- or 17-acetoxy moieties). Bile and urine from four baboons with biliary fistulas and urine from four intact baboons were collected for 7 hours. On the average, 40% and 44% of the injected dose were excreted in the bile and urine, respectively. Only 48% was recovered in the urine of intact baboons. Analysis of these excretion rates indicates an insignificant enterohepatic circulation of this compound. The steroid was excreted mostly (over 80%) as a glucosiduronate in urine and bile. Very little excretion of the 3-acetoxy compound was detected in the urine or bile at any time interval. 17-Monoacetoxy compounds, however, were detected both in urine and bile, suggesting a difference in the rate of in vivo hydrolysis of the 17beta- vs. the 3beta-acetate.