Rhesus monkey urine radioactivity

DEHP does not appear to be readily absorbed through the human skin. Wester et al. (1998) estimated that dermal absorption amounts to approximately 1.8% of a 24-hour applied dose of DEHP solubilized in ethanol. They noted that 1.1% of the radioactivity from a 24-hour dermal application of 14C-labeled DEHP to the forearm of volunteers was excreted in the urine within 7 days postapplication. They used this finding and the observation that approximately 60.8% of an intravenously-injected dose of DEHP was excreted in the urine of Rhesus monkeys over the same posttreatment time period as the basis for their estimate. No other reports were located regarding dermal absorption of DEHP in humans. 

Twenty-four hours after a single intravenous injection of 14C-DEHP to rats, the radioactivity was mainly recovered in the urine and feces, suggesting that the major excretory pathways in rats are the urine and bile (Schulz and Rubin 1973). Excretion was dose-dependent as shown by the fact that 50-60% of the injected radioactivity from a low dose was recovered in urine and feces, whereas less than 50% was recovered when a high dose was injected (Schulz and Rubin 1973). In Rhesus monkeys, 60.8% of the radioactivity in an intravenously injected dose of radiolabeled DEHP was excreted in the urine during 7 days postinjection, more than half of which was eliminated in the first day (Wester et al. 1998). 

The most significant information in the present study arises from a radically different approach to these metabolite investigations. Four years ago, we reported that an appreciable proportion of the total radioactivity in Rhesus monkey urine could be extracted with ether, even without prior hydrolysis (13). This excretion was highly pH-dependent -- with the curve s inflection point being near pH 4 (Figure 12) — indicating that the materials being extracted were probably carboxylic acids. 

Female Sprague-Dawley rats were exposed dermally to H]-benzo[a]pyrene (1 ppm) containing petroleum crude oil alone or in fortified soil matrix for 4 days (Yang et al. 1989). Recovery of radioactivity was 35.3% of the dose applied in oil, as follows urine (5.3% of dose), feces (27.5%), and tissues (2.5%) 96 hours after beginning of exposure. Recovery was 9.2% of applied dose with benzo[a]pyrene from petroleum crude-fortified soil recoveries in urine, feces, and tissues were 1.9%, 5.8%, and 1.5%, res 3ectively, at 96 hours. Benzo[a]pyrene (10 ppm) with acetone vehicle or in soil was applied to a 12 cm area of abdominal skin of female rhesus monkeys for 24 hours (Wester et al. 1990). Urine contained 51 22% of the dose with acetone vehicle and 13.2 3.4% with soil. 

In a related study. Wester et al. (1990,1993) assessed the in vivo percutaneous absorption of PCBs in adult female Rhesus monkeys. " C-Labeled Aroclor 1242 and 1254 were separately administered iv and topically to Rhesus monkeys and urinary and fecal excretion of radioactivity was measured for the next 30 days. Following iv administration, the 30-day cumulative excretion was 55% of the administered dose (39% urine, 16% feces) for Aroclor 1242 and 27% (7% urine, 20% feces) for Aroclor 1254. The percentage of the dose absorbed following topical administration to abdominal skin (after light clipping of hair) was estimated from the ratio of the total urinary and fecal excretion following topical and iv administration. Topical administration of Aroclor 1242 in soil, mineral oil, tiichlorobenzene, or acetone resulted in 14, 20, 18, and 21% absorption of the administered dose, respectively. In contrast to the above in vitro results with human skin, the vehicle had little effect on the systemic absorption of the PCBs applied to the skin of monkeys. This may be due to the uncertain viability of the human skin used in the in vitro studies and the fact that the in vitro study primarily assessed retention of PCBs in human skin and could not estimate systemic absorption. 

Percutaneous absorption of BP has been determined in Rhesus monkeys using " C-radiolabeled BP (Bronaugh et al. 1990). It should be noted that the purpose of this study was to examine the absorption and excretion of dermally-applied compounds used in fragrances, including BP. A single dose of radiolabeled-BP in acetone was applied to abdominal skin of the monkeys, and the level of radioactivity was monitored in the urine for up to 5 days. While 92.6 % of the radiolabel did appear in the urine of the monkeys, there was no attempt to determine the chemical nature the radioactive compounds that were excreted (e.g., parent BP or its metabohtes). 

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