Cholyllysyl fluroscein and related lysyl fluorescein conjugated bile acid analogues

There have been attempts to couple bile acids to fluorescein to permit their visualization during studies of physiology and pathophysiology. Although conjugation has been achieved by many, the product differed in many respects from the parent bile acid congener. We describe lysylfluorescein conjugated bile acid analogues (LFCBAA) synthesized in our laboratory as model divalent "unipolar" molecules. We have determined LFCBAA properties including their water:octanol partition coefficient, HPLC retention time and critical micellar concentration and compared them with their parent bile acid congeners. Cholyl lysylfluorescein (CLF) and lithocholyl lysylfluoroscein (LLF) have properties similar to cholylglycine (CG) and glycolithocholate (GLC), respectively. In human and rat hepatocytes uptake of CLF follows Michaelis-Menten kinetics with K(m) and Vmax similar to CG. Biliary excretion rates of CLF and LLF closely resemble those of CG and GLC in both normal and mutant TR- rats which lack the multiorganic anion transporter (MOAT), strongly supporting the notion that CLF and LLF are substrates for the canalicular bile salt transporter (cBST). The close similarity of hepatocyte uptake and biliary secretion of these LFCBAA and their parent bile acid congeners makes them potentially useful probes for the intracellular visualization of bile salt movement and deposition in various models of bile formation and secretion.