This proposal seeks to study the distribution, mechanism, and regulation of H/HCO3 transport in the rat inner medullary collecting duct (IMCD). Previous studies have established that the IMCD is a major site of urinary acidification and net acid secretion. Recent morphologic and functional studies have extensively examined the mechanisms and regulation of H/HCO3 transport in the cortical and outer medullary collecting duct. The IMCD has not been studied previously by in vitro microperfusion because of its technical difficulty. Due to a number of recent technical advances, it is now possible to dissect the IMCD from germ-free animals. We will isolate and perfuse the IMCD in vitro permitting us to (1) determine the axial distribution of H/HCO3 transport along the IMCD; (2) identify the mechanism of transport using fluorescent measurements of cell pH; (3) identify the cell types which secrete protons with fluorescent and optical microscopy; and (4) determine the mechanism of regulation of transepithelial transport using all the above techniques. These studies will supply insights into the pathway which mediates proton secretion in the terminal portion of the nephron and will provide a better understanding of the role of the IMCD in renal acid-base balance. During my postdoctoral training at the NIH with Dr. Maurice Burg, I learned the techniques of in vitro microperfusion and fluorescence microscopy, and I used these to examine the mechanisms of HCO3 and ammonia transport in the proximal tubule and collecting duct segments. These techniques have been successfully transferred to my new laboratory at Southwestern Medical School. I will now apply these techniques (along with a more sensitive assay for total CO2 which I developed specially for these studies), to address the above problems in the rat inner medullary collecting duct. My sponsor, Dr. Robert Alpern, has extensive experience performing similar studies in the proximal tubule and will be involved extensively in the supervision of these studies. In addition, Dr. Donald Seldin, who has a longstanding interest in distal acidification, will also be involved.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Clinical Investigator Award (CIA) (K08)
Project #
5K08DK001888-04
Application #
3080751
Study Section
Diabetes, Endocrinology and Metabolic Diseases B Subcommittee (DDK)
Project Start
1989-04-15
Project End
1994-03-31
Budget Start
1992-04-01
Budget End
1993-03-31
Support Year
4
Fiscal Year
1992
Total Cost
Indirect Cost
Name
University of Texas Sw Medical Center Dallas
Department
Type
Schools of Medicine
DUNS #
City
Dallas
State
TX
Country
United States
Zip Code
75390
Tank, J E; Moe, O W; Star, R A et al. (1996) Differential regulation of rat glomerular and proximal tubular renin mRNA following uninephrectomy. Am J Physiol 270:F776-83
Lau, K S; Nakashima, O; Aalund, G R et al. (1995) TNF-alpha and IFN-gamma induce expression of nitric oxide synthase in cultured rat medullary interstitial cells. Am J Physiol 269:F212-7
Star, R A; Rajora, N; Huang, J et al. (1995) Evidence of autocrine modulation of macrophage nitric oxide synthase by alpha-melanocyte-stimulating hormone. Proc Natl Acad Sci U S A 92:8016-20
Shaul, P W; North, A J; Brannon, T S et al. (1995) Prolonged in vivo hypoxia enhances nitric oxide synthase type I and type III gene expression in adult rat lung. Am J Respir Cell Mol Biol 13:167-74
Ujiie, K; Yuen, J; Hogarth, L et al. (1994) Localization and regulation of endothelial NO synthase mRNA expression in rat kidney. Am J Physiol 267:F296-302
North, A J; Star, R A; Brannon, T S et al. (1994) Nitric oxide synthase type I and type III gene expression are developmentally regulated in rat lung. Am J Physiol 266:L635-41
Ujiie, K; Hogarth, L; Danziger, R et al. (1994) Homologous and heterologous desensitization of a guanylyl cyclase-linked nitric oxide receptor in cultured rat medullary interstitial cells. J Pharmacol Exp Ther 270:761-7
Ujiie, K; Drewett, J G; Yuen, P S et al. (1993) Differential expression of mRNA for guanylyl cyclase-linked endothelium-derived relaxing factor receptor subunits in rat kidney. J Clin Invest 91:730-4
Star, R A; Gillin, A D; Parikh, V J et al. (1993) The urease inhibitor acetohydroxamic acid is transported by the urea pathway in rat terminal IMCD. Am J Physiol 265:F385-90
Gillin, A G; Star, R A; Sands, J M (1993) Osmolarity-stimulated urea transport in rat terminal IMCD: role of intracellular calcium. Am J Physiol 265:F272-7

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