Collecting duct alpha intercalated cells secrete protons and absorb bicarbonate. The ATP that is utilized for H+ secretion derives at least in part from glycolysis. Collecting duct glycolysis produces substantial amounts of lactic acid, but it is not understood how lactate exits the intercalated cell or what factors regulate this step. We have used functional assays to show that cells of the collecting duct cell line MDCK have a basolateral membrane lactate/H+ co-transporter. We have also shown that a monoclonal antibody to the rabbit erythrocyte lactate/H+ co-transporter recognizes similar proteins in the rabbit kidney on immunoblots, and immunocytochemically labels the basolateral membranes of rabbit kidney proximal tubule, medullary thick ascending limb, and collecting duct, especially intercalated cells. The amount of the transporter in the collecting ducts appears to be increased by carbohydrate loading the animal, suggesting that it is regulated as a function of metabolism. We have created a rabbit kidney cDNA library, screened it with this antibody, and have a positive clone. Based on these results, we ask the following questions: 1. Does lactate cross the basolateral membrane of intercalated cells via a lactate/H+ co-transporter? 2. What is the structure of this transporter? 3. What regulates the lactate/H+ co-transporter? We have three corresponding Specific Aims: 1. Determine the intracellular localization, size, and functional properties of the rabbit collecting duct lactate/H+ co-transporter. 2. Clone, sequence, and express the cDNA of the rabbit kidney lactate/H+ co-transporter. 3. Quantitate the changes in lactate/H+ co-transporter function, mRNA, and protein amount in response to changes in metabolism. The methods that will be used include perfused tubules, cultured collecting duct cells, immuno- and mRNA blotting, immunocytochemistry, digital imaging spectrofluorometry, and cDNA cloning and sequencing. The proposed experiments will advance our understanding of a fundamental aspect of intercalated cell function: the mechanism by which lactate is transported across the basolateral membrane.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
5R01DK038095-07
Application #
2140273
Study Section
General Medicine B Study Section (GMB)
Project Start
1988-12-01
Project End
1995-04-30
Budget Start
1994-05-01
Budget End
1995-04-30
Support Year
7
Fiscal Year
1994
Total Cost
Indirect Cost
Name
Albert Einstein College of Medicine
Department
Internal Medicine/Medicine
Type
Schools of Medicine
DUNS #
009095365
City
Bronx
State
NY
Country
United States
Zip Code
10461
Schuster, V L; Lu, R; Kanai, N et al. (1996) Cloning of the rabbit homologue of mouse 'basigin' and rat 'OX-47': kidney cell type-specific expression, and regulation in collecting duct cells. Biochim Biophys Acta 1311:13-9
Kanai, N; Lu, R; Bao, Y et al. (1996) Estradiol 17 beta-D-glucuronide is a high-affinity substrate for oatp organic anion transporter. Am J Physiol 270:F326-31
Kanai, N; Lu, R; Bao, Y et al. (1996) Transient expression of oatp organic anion transporter in mammalian cells: identification of candidate substrates. Am J Physiol 270:F319-25
Lu, R; Kanai, N; Bao, Y et al. (1996) Regulation of renal oatp mRNA expression by testosterone. Am J Physiol 270:F332-7
Kanai, N; Lu, R; Satriano, J A et al. (1995) Identification and characterization of a prostaglandin transporter. Science 268:866-9
Rosenberg, S O; Fadil, T; Schuster, V L (1993) A basolateral lactate/H+ co-transporter in Madin-Darby Canine Kidney (MDCK) cells. Biochem J 289 ( Pt 1):263-8
Schuster, V L (1993) Function and regulation of collecting duct intercalated cells. Annu Rev Physiol 55:267-88
Ostedgaard, L S; Jennings, M L; Karniski, L P et al. (1991) A 45-kDa protein antigenically related to band 3 is selectively expressed in kidney mitochondria. Proc Natl Acad Sci U S A 88:981-5
Emmons, C L; Matsuzaki, K; Stokes, J B et al. (1991) Axial heterogeneity of rabbit cortical collecting duct. Am J Physiol 260:F498-505
Schuster, V L; Fejes-Toth, G; Naray-Fejes-Toth, A et al. (1991) Colocalization of H(+)-ATPase and band 3 anion exchanger in rabbit collecting duct intercalated cells. Am J Physiol 260:F506-17

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