The objectives of the present proposal are to pursue the discovery that prolactin (PRL) increases the transport of taurocholate (TC), a major bile acid, across the hepatocyte. TC transport is decreased in pregnancy when PRL levels are low, but rebounds post partum when PRL levels are high. The rebound post partum can be prevented by blockade of PRL secretion, and treatment of rats with ovine PRL (oPRL) increases the transport of TC in a dose-dependent manner. The general objectives are to characterize further the changes in transport seen post partum and following oPRL treatment and to identify the mechanism(s) by which PRL increases TC transport.
The specific aims are to 1) characterize the time course of the changes in TC transport throughout lactation, 2) determine if transport of other substrates, specifically nobile acid organic anions, is increased post partum an by treatment of rats wit oPRL, 3) test the hypothesis that PRL increases TC transport by increasing the hepatocytes membrane potential, 4) test the hypothesis the PRL increases Na/TC cotransport by increasing synthesis of messenger RNA and synthesis of transport protein, 5)test the hypothesis that PRL increases TC transport across the canalicular membrane by increasing synthesis of messenger RNA and synthesis of the ecto-ATPase/bile acid transporter protein, and 6) characterize Na+/TC cotransport in basolateral plasma membrane vesicles and potential dependent and ATP- dependent transport of TC in canalicular membrane vesicles and potential- dependent and ATP-dependent transport of TC in canalicular membrane vesicle in controls s oPRL-treated rats. Approaches used to answer these questions include measurements of the secretory rate maximum for transport in isolated hepatocytes, characterization of transport in basolateral and canalicular membrane vesicles, quantitation of changes in messenger RNA using cDNA probes to the Na+/TC cotransporter and the ecto-ATPase/bile acid transporter, quantitate rates of nuclear transcription of message of these genes, and use of specific antibodies to quantitate transport proteins. The finding that PRL increases TC transport capacity in a mammalian species suggests the possibility of similar functions in humans, particularly in women. Characterization of the mechanisms by which PRL increases TC transport is essential for understanding the normal physiology and regulation of these studies is therefore to understand the mechanisms by which PRL regulates TC transport and bile secretory function in order to develop effective therapeutic interventions in cholestatic liver disease.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
5R01DK046923-04
Application #
2414848
Study Section
General Medicine A Subcommittee 2 (GMA)
Project Start
1994-05-01
Project End
1999-04-30
Budget Start
1997-05-01
Budget End
1999-04-30
Support Year
4
Fiscal Year
1997
Total Cost
Indirect Cost
Name
University of Kentucky
Department
Pharmacology
Type
Schools of Medicine
DUNS #
832127323
City
Lexington
State
KY
Country
United States
Zip Code
40506
Athippozhy, Antony; Huang, Liping; Wooton-Kee, Clavia Ruth et al. (2011) Differential gene expression in liver and small intestine from lactating rats compared to age-matched virgin controls detects increased mRNA of cholesterol biosynthetic genes. BMC Genomics 12:95
Wooton-Kee, Clavia Ruth; Coy, Donna J; Athippozhy, Antony T et al. (2010) Mechanisms for increased expression of cholesterol 7alpha-hydroxylase (Cyp7a1) in lactating rats. Hepatology 51:277-85
Wooton-Kee, Clavia Ruth; Cohen, David E; Vore, Mary (2008) Increased cholesterol 7alpha-hydroxylase expression and size of the bile acid pool in the lactating rat. Am J Physiol Gastrointest Liver Physiol 294:G1009-16
Wood, M; Ananthanarayanan, M; Jones, B et al. (2005) Hormonal regulation of hepatic organic anion transporting polypeptides. Mol Pharmacol 68:218-25
Cao, Jingsong; Wood, Marcie; Liu, Yong et al. (2004) Estradiol represses prolactin-induced expression of Na+/taurocholate cotransporting polypeptide in liver cells through estrogen receptor-alpha and signal transducers and activators of transcription 5a. Endocrinology 145:1739-49
Mottino, Aldo D; Hoffman, Tim; Dawson, Paul A et al. (2002) Increased expression of ileal apical sodium-dependent bile acid transporter in postpartum rats. Am J Physiol Gastrointest Liver Physiol 282:G41-50
Cao, J; Gowri, P M; Ganguly, T C et al. (2001) PRL, placental lactogen, and GH induce NA(+)/taurocholate-cotransporting polypeptide gene expression by activating signal transducer and activator of transcription-5 in liver cells. Endocrinology 142:4212-22
Cao, J; Huang, L; Liu, Y et al. (2001) Differential regulation of hepatic bile salt and organic anion transporters in pregnant and postpartum rats and the role of prolactin. Hepatology 33:140-7
Mottino, A D; Hoffman, T; Jennes, L et al. (2001) Expression of multidrug resistance-associated protein 2 in small intestine from pregnant and postpartum rats. Am J Physiol Gastrointest Liver Physiol 280:G1261-73
Ganguly, T C; O'Brien, M L; Karpen, S J et al. (1997) Regulation of the rat liver sodium-dependent bile acid cotransporter gene by prolactin. Mediation of transcriptional activation by Stat5. J Clin Invest 99:2906-14

Showing the most recent 10 out of 13 publications