The candidate is a productive young investigator firmly committed to an academic research career. Based on her findings while a research trainee, she has developed two new hypotheses regarding the mechanisms of canalicular bile formation and the pathogenesis of cholestasis. These hypotheses form the basis for this research proposal. First, while there is now compelling evidence that hepatic bile acid uptake is dependent upon a sodium-coupled uptake step driven by the electrochemical sodium gradient maintained by Na, K-ATPase, the relationship between Na,K-ATPase cation pumping and bile acid-dependent bile flow (BADBF) is poorly understood. The hypothesis that primary changes in Na,K-ATPase cation pumping play a role in cholestasis will be tested using, as probes, chlorpromazine and estrogen, compounds known to inhibit Na,K-ATPase in isolated membranes. The following questions will be addressed: 1) Do chlorpromazine and estrogen also inhibit cation pumping in the intact cell? 2) Do these agents diminish the electrochemical sodium gradient, thereby inhibiting sodium-coupled uptake of bile acids and BADBF sufficient to cause cholestasis? Second, previous findings suggest that HCO3- secretion accounts for much of bile acid-independent bile flow (BAIBF). The candidate postulates that hepatic HCO3- secretion is mediated, at least in part, by a plasma membrane proton translocating ATPase (H+ ATPase). This proposal will look for such a H+ ATPase, characterize its function and examine its role in BAIBF and certain forms of cholestasis. These hypotheses will be tested using cultured rat hepatocytes, liver plasma membrane vesicles and the perfused rat liver, techniques already established in this laboratory. The findings will provide important new insight into the mechanisms of canalicular bile formation and the pathophysiology of cholestasis, as well as information regarding poorly understood aspects of epithelial function in general, including: 1) the functional relationships between Na,K-ATPase cation pumping, sodium-coupled solute uptake and modulation of epithelial transport, and 2) the role of active H+ transport in the sponsorship of Dr. Bruce Scharschmidt within the stimulating and productive research environment of UCSF and the Liver Center where the candidate will interact with a community of active investigators engaged in the study of epithelial transport and hepatic physiology.

Project Start
1984-04-01
Project End
1987-03-31
Budget Start
1985-04-01
Budget End
1986-03-31
Support Year
2
Fiscal Year
1985
Total Cost
Indirect Cost
Name
University of California San Francisco
Department
Type
Schools of Medicine
DUNS #
073133571
City
San Francisco
State
CA
Country
United States
Zip Code
94143
Van Dyke, R W; Belcher, J D (1994) Acidification of three types of liver endocytic vesicles: similarities and differences. Am J Physiol 266:C81-94
Renner, E L; Lake, J R; Cragoe Jr, E J et al. (1988) Ursodeoxycholic acid choleresis: relationship to biliary HCO-3 and effects of Na+-H+ exchange inhibitors. Am J Physiol 254:G232-41
Van Dyke, R W (1988) Proton pump-generated electrochemical gradients in rat liver multivesicular bodies. Quantitation and effects of chloride. J Biol Chem 263:2603-11
Renner, E L; Lake, J R; Cragoe Jr, E J et al. (1988) Amiloride and amiloride analogs inhibit Na+/K+-transporting ATPase and Na+-coupled alanine transport in rat hepatocytes. Biochim Biophys Acta 938:386-94
Van Dyke, R W; Scharschmidt, B F (1987) Effects of chlorpromazine on Na+-K+-ATPase pumping and solute transport in rat hepatocytes. Am J Physiol 253:G613-21
Scharschmidt, B F; Lake, J R; Renner, E L et al. (1986) Fluid phase endocytosis by cultured rat hepatocytes and perfused rat liver: implications for plasma membrane turnover and vesicular trafficking of fluid phase markers. Proc Natl Acad Sci U S A 83:9488-92
Van Dyke, R W (1986) Anion inhibition of the proton pump in rat liver multivesicular bodies. J Biol Chem 261:15941-8
Niederau, C; Van Dyke, R W; Scharschmidt, B F et al. (1986) Rat pancreatic zymogen granules. An actively acidified compartment. Gastroenterology 91:1433-42
Van Dyke, R W; Hornick, C A; Belcher, J et al. (1985) Identification and characterization of ATP-dependent proton transport by rat liver multivesicular bodies. J Biol Chem 260:11021-6