Interaction of bumetanide derivatives with hepatocellular bile acid uptake

The loop diuretic bumetanide is an organic monocarboxylic organic anion assumed to be transported into hepatocytes by a transport system for bile acids. The structural requirements of 22 bumetanide analogues were analyzed for an interaction with bile acid uptake into isolated rat hepatocytes. Whereas bumetanide inhibited the hepatocellular uptake of [14C]cholate to the same degree as its own uptake, derivatization altered affinity and specificity and yielded compounds that selectively inhibited either cholate or taurocholate uptake or uptake of both. No correlation was found between the diuretic potency of bumetanide derivatives, reflecting the affinity to the Na(+)-K(+)-Cl- cotransporter, and their affinity to hepatic bile salt transport. Computer-aided model building combined with the calculation of potential energy maps showed a strictly amphipathic charge separation in bumetanide analogues as in bile acids. Ranking bumetanide compounds by their mean inhibitory concentration values, inhibition constant...