CHOLYLLYSYL FLUROSCEIN AND RELATED LYSYL FLUORESCEIN CONJUGATED BILE-ACID ANALOGS

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 lysyl fluorescein conjugated bile acid analogues (LFCBAA) synthesized in our laboratory as model divalent ''unipolar'' molecules. We have determin ed LFCBAA properties including their water:octanol partition coefficie nt, HPLC retention time and critical micellar concentration and compar ed 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 hu man and rat hepatocytes uptake of CLF follows Michaelis-Menten kinetic s with K-m and V-max 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 canalicu lar bile salt transporter (cBST). The close similarity of hepatocyte u ptake 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 o f bile formation and secretion.