In vivo metabolism of unconjugated or conjugated estradiol-17 beta in the dog kidney (author's transl)

Abstract

Estradiol-17β (E2) has recently been reported to be conjugated into its glucosiduronate or sulfate in human or baboon kidneys in vivo or in vitro. To investigate whether glucosiduronation or sulfation of E2 occurs in the dog kidney in vivo and to clarify the fate of conjugated E2 in the kidney, this experiment was performed using the following techniques.1) 3H labeled unconjugated or conjugated E2 was, injected into one of the renal arteries and 14C labeled unconjugated E2 was simultaneously injected into a peripheral vein of a dog (shown as Fig. 1).2) Following the injection, urine from both sides was collected separately through ureterostomies at various time intervals over a period of 7 hours.3) Aliquots of the collected urine samples were counted for radioactivity.4) The metabolites in the collected urine samples were identified on the DEAE Sephadex A-25 column chromatography, enzyme hydrolysis, and thin layer chromatography, using two different solvent systems : chloroform-ethyl ether, 1 : 4 and cyclohexane-ethyl acetate, 1 : 1.In the first experiment, the simultaneous injection of (6, 7-3H) E2 into a right and (4-14C) E2 into a peripheral vein, the excretion of 3 H labeled compounds in the injected side was about five times greater than it was in the opposite side in the early interval (for 15 min. following the injection), and the 3H/14C ratio in the injected side was about ten times what it was in the initial ratio. Urine samples in the injected side in the early interval were mainly composed of 3H labeled unconjugated E2 (shown as Fig. 3). In all experimental time intervals, 14 C compounds were excreted at almost equal percentages in both sides for 7 h. following the injection (shown as Fig. 2). When (6, 7-3H) E2-3G or (6, 7-3H) E2-17G was injected into a renal artery, it was also excreted directly through the kidney without any change in the form in the early intervals (shown as Fig. 5 and Fig. 6). Metabolites in the urine samples in the late intervals were identified as estrogen glucosiduronates (E1-3G and E2-3G) and estrogen sulfates (E1-S and E2-17α-S) following the above procedures, and E2 was changed to E1 in small amounts. Accordingly, glucosiduronation did not occur in dog kidneys in vivo, and these metabolites were thought to have occurred in the systemic circulation.In the second experiment, the simultaneous injection of (2, 4, 6, 7-3H) E2 or (2, 4, 6, 7, 16, 17-3H) E2 into a renal artery and (4-14C) E2 into a peripheral vein, the total excretion of 3H compounds (34% or 46% on an average following a renal injection of (2, 4, 6, 7-3H) E2 or (2, 4, 6, 7, 16, 17-3H) E2, respectively) was higher in comparison with the first experiment (14% on an average following a renal injection of (6, 7-3H) E2). The 3H/14C ratios in the second experiment were about ten times that of the first experiment (shown as Table 2). Therefore, E2 was thought to be metabolized at the 6, 7 position in the systemic level.As shown above, the metabolism of unconjugated or conjugated E2 in the dog kidney in vivo and metabolism at the 6, 7 position of E2 in the systemic level were clarified in these experiments.