The effect of mannitol and secretin on the biliary transport of urate in humans.

No evidence is available on the transport of biliary urate and the possible role of choleretic agents in the regulation of biliary urate elimination in humans. To test this hypothesis we studied the following: (1) 45 cholecystomized patients to determine urate levels in hepatic bile and gallbladder bile, and (2) 13 cholecystomized patients fitted with T-tubes to determine the effects of secretin injection (either 70 U of porcine secretin or 0.02 mg.kg-1 of synthetic human secretin, as a single dose) and/or mannitol infusion (5 cm3.min-1 for 90 minutes) on biliary urate excretion. In the latter group, samples of bile and serum were analyzed for urate under basal state and after the administration of both agents. In our first approach, results showed that urate concentrations present in hepatic as well as in gallbladder bile were much lower than the corresponding values in serum (P < .001). The mean gallbladder bile urate concentration was not significantly increased over the concentration in hepatic bile. When compared with basal state values, procine and synthetic secretin induced a significant increase in mean urate clearance (P < .001) because of a significant increase in mean bile flow (P < .001), whereas the mean biliary urate concentration significantly decreased (P < .001) with a concomitant decrease in the mean serum urate concentration (P < .02). Mannitol also induced a significant increase in the mean urate clearance (P < .002) because of a significant increase in the mean biliary urate concentration (P < .01) with a concomitant decrease in the mean serum urate concentration (P < .01) and without changes in the mean bile flow (P > .05). Therefore, it appears that a substantial amount of urate is eliminated by biliary route. The load of biliary urate excreted may be modified by mannitol and secretin and possibly other factors, a finding that could have an application in some pathological conditions associated with decreased renal urate excretion.