title: Regulation of the renal Na-HCO3 cotransporter: IX. Modulation by insulin, epidermal growth factor and carbachol.
abstract: To examine the role of tyrosine kinase (TK) on basolateral membrane (BLM) transport, we looked for the presence of TK activity in these membranes and showed that the synthetic substrate for TK, poly [Glu80 Na, Tyr20] caused a three-fold increase in tyrosine phosphorylation. This effect was completely blocked by the TK inhibitors, 2-hydroxy-5(2,5-dihydroxybenzyl) aminobenzoic acid (HAC), 1 microM, and methyl 2,5-dihydroxycinnamate (DHC), 5 microM. We then examined the effect of agents that cause TK stimulation on tyrosine kinase immunocontent and on the Na-HCO3 cotransporter activity in BLM and in primary cultures of the proximal tubule. We utilized the cholinergic agent, carbachol (10(-4) M), epidermal growth factor (EGF 10(-8) M), and insulin (10(-8) M), well known activators of TK. Carbachol, insulin, and EGF caused a significant increase in TK immunoreactive protein content which was blocked by HAC and DHC. In BLM, carbachol significantly stimulated HCO3-dependent 22Na uptake and this effect was totally prevented by the monoclonal antibody against TK. In cultured proximal tubule cells, carbachol, EGF and insulin at physiologic concentration caused a significant stimulation of the cotransporter activity and this effect was completely blocked by the TK inhibitor, HAC. Increasing the dose of insulin 100-fold did not cause further stimulation of the cotransporter indicating that insulin plays a permissive role on the cotransporter. These results demonstrate the presence of TK in renal proximal tubule cells and show that activation of this kinase by dissimilar agents enhance the activity of the Na-HCO3 cotransporter.
authors.affiliation: Section of Nephrology, University of Illinois at Chicago, 60612-7315, USA.
authors.forename: O S
authors.initials: OS
authors.lastname: Ruiz
authors.forename: Y Y
authors.initials: YY
authors.lastname: Qiu
authors.forename: L R
authors.initials: LR
authors.lastname: Cardoso
authors.forename: J A
authors.initials: JA
authors.lastname: Arruda
mesh_terms: D062365:Aminobenzoates / Q000494:pharmacology; D000818:Animals; D000906:Antibodies / Q000494:pharmacology; D002352:Carrier Proteins / Q000378:metabolism*; D002478:Cells, Cultured; D002934:Cinnamates / Q000494:pharmacology; D004789:Enzyme Activation / Q000502:physiology; D004815:Epidermal Growth Factor / Q000494:pharmacology*; D019833:Genistein / Q000494:pharmacology; D007328:Insulin / Q000494:pharmacology*; D036341:Intercellular Signaling Peptides and Proteins; D007684:Kidney Tubules / Q000187:drug effects*; D008565:Membrane Proteins / Q000032:analysis; D010455:Peptides / Q000378:metabolism; D010766:Phosphorylation; D019000:Phosphotyrosine / Q000276:immunology; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D011817:Rabbits; D012459:Salicylates; D027982:Sodium-Bicarbonate Symporters; D062368:meta-Aminobenzoates
chemical_list: D062365:Aminobenzoates; D000906:Antibodies; D002352:Carrier Proteins; D002934:Cinnamates; D007328:Insulin; D036341:Intercellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D010455:Peptides; D012459:Salicylates; D027982:Sodium-Bicarbonate Symporters; D062368:meta-Aminobenzoates; C073254:2-hydroxy-5-(2,5-dihydrobenzyl)aminobenzoic acid; D019000:Phosphotyrosine; C027606:L-glutamic acid-L-tyrosine copolymer; D004815:Epidermal Growth Factor; C067472:methyl 2,5-dihydroxycinnamate; D019833:Genistein; D011505:Protein-Tyrosine Kinases