We propose to better understand the causes of diarrheal diseases by studying the intracellular regulation of active intestinal electrolyte transport. We will concentrate on the role of Ca++ and calmodulin in regulation of active rabbit ileal electrolyte transport and will determine 1) whether the Na+ absorptive cell is regulated by changes in intracellular Ca++; 2) whether a Na+/Ca++ plasma membrane exchange process is involved as a physiologic regulator of active ion transport; 3) whether intracellular calcium stores are involved in regulation of basal absorption and stimulated secretion; 4) whether Ca++ calmodulin is involved in regulation of basal absorption and stimulated secretion; and 5) whether drugs which alter Ca++ calmodulin-modulated functions in other tissues affect active intestinal ion transport. The goals of this proposal are to understand regulation of basal absorption and stimulated secretion with an ultimate goal of modifying active intestinal transport in such a way as to be useful in therapy of diarrheal diseases. The methodologies to be used will include: 1) Na+ and C1- transport; measurements of active transcellular transport and influx of Na+ and C1- using the Ussing chamber-voltage clamp technique using radioactive tracers; 2) involvement of Ca++: 45Ca++ influx and efflux using radioactive calcium with an extracellular space marker, and calcium content measurements by atomic absorption spectrometry; 3) involvement of cyclic nucleotides: measurement of intestinal content of the cyclic nucleotides cyclic AMP and cyclic GMP and activities of the intestinal mucosal enzymes adenylate cyclase, guanylate cyclase and phosphodiesterase.

Project Start
1980-03-01
Project End
1987-02-28
Budget Start
1985-03-01
Budget End
1986-02-28
Support Year
6
Fiscal Year
1985
Total Cost
Indirect Cost
Name
Tufts University
Department
Type
DUNS #
City
Boston
State
MA
Country
United States
Zip Code
Maher, M M; Gontarek, J D; Bess, R S et al. (1997) The Na+/H+ exchange isoform NHE3 regulates basal canine ileal Na+ absorption in vivo. Gastroenterology 112:174-83
Tse, C M; Ma, A I; Yang, V W et al. (1991) Molecular cloning and expression of a cDNA encoding the rabbit ileal villus cell basolateral membrane Na+/H+ exchanger. EMBO J 10:1957-67
Cohen, M E; Reinlib, L; Watson, A J et al. (1990) Rabbit ileal villus cell brush border Na+/H+ exchange is regulated by Ca2+/calmodulin-dependent protein kinase II, a brush border membrane protein. Proc Natl Acad Sci U S A 87:8990-4
Rood, R P; DeLellis, R A; Dayal, Y et al. (1988) Pancreatic cholera syndrome due to a vasoactive intestinal polypeptide-producing tumor: further insights into the pathophysiology. Gastroenterology 94:813-8
Dartt, D A; Mircheff, A K; Donowitz, M et al. (1988) Ca2+ - and cAMP-induced protein phosphorylation in lacrimal gland basolateral membranes. Am J Physiol 254:G543-51
Donowitz, M; Emmer, E; McCullen, J et al. (1987) Freeze-thaw and high-voltage discharge allow macromolecule uptake into ileal brush-border vesicles. Am J Physiol 252:G723-35
Sharp, G W; Hannah-White, C; el-Sabban, M et al. (1987) Effects of Ca2+, theophylline and promethazine on protein phosphorylation in intact cells of rabbit ileum. Correlation with active Na and Cl absorption. FEBS Lett 221:309-14
Takaori, K; Burton, J; Donowitz, M (1986) The transport of an intact oligopeptide across adult mammalian jejunum. Biochem Biophys Res Commun 137:682-7
Donowitz, M; Cusolito, S; Sharp, G W (1986) Effects of calcium antagonist TMB-8 on active Na and Cl transport in rabbit ileum. Am J Physiol 250:G691-7
Cohen, M E; Sharp, G W; Donowitz, M (1986) Suggestion of a role for calmodulin and phosphorylation in regulation of rabbit ileal electrolyte transport: effects of promethazine. Am J Physiol 251:G710-7

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