Abstract
Glycolysis uncoupled from glucose oxidation is a major reason for the intracellular acidosis that occurs during severe myocardial ischemia. The imbalance between glycolysis and glucose oxidation, and the resultant H+ produced from glycolytically derived ATP hydrolysis in the diabetic rat heart is the focus of this study. Isolated working hearts from 6 week streptozotocin diabetic rat hearts were perfused with 11 mM glucose and 1.2 mM palmitate and subjected to a 25 min period of global ischemia. A second series of experiments were also performed in which hearts from control, diabetic, and islet-transplanted diabetic rats were subjected to a 30 min aerobic perfusion, followed by a 60 min period of low-flow ischemia (coronary flow = 0.5 ml/min) and 30 min of aerobic reperfusion. H+ production from glucose metabolism was measured throughout the two protocols by simultaneous measurement of glycolysis and glucose oxidation using perfusate labelled with [5-3H/U-14C]-glucose. Rates of H+ production were calculated by measuring the difference between glycolysis and glucose oxidation. The H+ production throughout the perfusion was generally lower in diabetic rat hearts compared to control hearts, while islet-transplantation of diabetic rats increased H+ production to rates similar to those seen in control hearts. This occurred primarily due to a dramatic increase in the rates of glycolysis. Despite the difference in H+ production between control, diabetic and islet-transplanted diabetic rat hearts, no difference in mRNA levels of the cardiac Na+/H+-exchanger (NHE-1) was seen. This suggests that alterations in the source of protons (i.e. glucose metabolism) are as important as alterations in the fate of protons, when considering diabetes-induced changes in cellular pH. Furthermore, our data suggests that alterations in Na+/H+-exchange activity in the diabetic rat heart occur at a post-translational level, possibly due to direct alterations in the sarcolemmal membranes.
Similar content being viewed by others
References
Meng HP, Maddaford TG, Pierce GN: Effect of amiloride and selected analogues on postischemic recovery of cardiac contractile function. Am J Physiol 264: H1831–H1835, 1990
Tani M, Neely JR: Role of intracellular Na+ in Ca2+ overload and depressed recovery of ventricular function of reperfused ischemic rat hearts. Circ Res 65: 1945–1956, 1989
Pierce G., Ramjiawan B, Dhalla NS, Ferrari R: Na+-H+ exchange in cardiac sarcolemmal vesicles isolated from diabetic rats. Am J Physiol 258: H255–H261, 1990
Khandoudi N, Bernard M, Cozzone P, Feuvray D: Intracellular pH and role of Na+-H+ exchange during ischemia and reperfusion of normal and diabetic rat hearts. Cardiovas Res 24: 873–878, 1990
Lopaschuk GD, Saddik M, Barr R, Huang L, Barker CC, Muzyka RA: Effects of high levels of fatty acids on functional recovery of ischemic hearts from diabetic rats. Am J Physiol 263: E1046–E1053, 1993
Tani M, Neely JR: Hearts from diabetic rats are more resistant to in vitro ischemia: Possible role of altered Ca2+ metabolism. Circ Res 62: 931–940, 1988
Opie LH: Myocardial ischemia – metabolic pathways and implications of increased glycolysis. Cardiovas Drugs Ther 4: 777–790, 1990
Dyck JRB, Lopaschuk GD, Fliegel L: Identification of a small Na+/H+ exchanger-like message in the rabbit myocardium. FEBS Lett 310: 255–259, 1992
Garland PB, Randle PJ: Regulation of glucose uptake by muscle. 10. Effects of alloxan diabetes, starvation, hypophysectomy and adrenalectomy and of fatty acids, ketone bodies and pyruvate on the glycerol output and concentrations of free fatty acids, long-chain fatty acyl coenzyme A, glycerol phosphate and citrate cycle intermediates in rat hearts and diaphragm muscles. Biochem J 93: 678, 1964
Goodale WT, Olson RE, Hackel DB: The effects of fasting and diabetes mellitus on myocardial metabolism in man. Am J Medicine: 212–220, 1959
Randle PJ, Hales CN, Garland PB, Newsholme EA: The glucose fatty-acid cycle. Its role in insulin sensitivity and the metabolic disturbances of diabetes mellitus. Lancet 1: 785–789, 1963
Bidet M, Merot J, Tauc M, Poujeol P: Na+-H+ exchanger in proximal cells isolated from kidney. II. Short-term regulation by glucocorticoids. Am J Physiol 253: F945–F951, 1987
Freiberg JM, Kinsella J, Sacktor B: Glucocorticoids increase the Na+-H+ exchange and decrease the Na+ gradient-dependent phosphateuptake systems in renal brush border membrane vesicles. Proc Natl Acad Sci USA 79: 4932–4936, 1982
Kinsella JL, Cujdik T, Sacktor B: Na+-H+ exchanger in isolated renal brush-border membrane vesicles in response to metabolic acidosis. J Biol Chem 259: 13224–13227, 1984
Tse C-M, Ma AF, Yang VW, Watson AJM, Levine S, Montrose MH, Potter J, Sardet C, Pouyssegur J, Donnowitz M: Molecular cloning and expression of a cDNA encoding the rabbit ileal villus cell basolateral membrane Na+/H+ exchanger. EMBO J 10: 1957–1967, 1991
Rao GN, Sardet C, Pouyssegur J, Berk BC: Differential regulation of Na+/H+ antiporter gene expression in vascular smooth muscle cells by hypertrophic and hyperplastic stimuli. J Biol Chem 265: 19393–19396, 1990
Moe OW, Miller RT, Horie S, Caro A, Preisig PA, Arper PR: Differential regulation of Na/H antiporter by acid in renal epithelial cells and fibroblasts. J Clin Invest 88: 1703–1708, 1991
Fliegel L, Sardet C, Pouyssegur J, Barr A: Identification of the protein and cDNA of the cardiac Na+/H+ exchanger. FEBS Lett 279: 25–29, 1991
Rajotte RV, Warnock GL, Coulombe MG: In: R van Schlifgaard, MA Hardy (eds). Transplantation of the Endocrine Pancreas in Diabetes Mellitus. Elsevier Sciences Publishers, BV Amsterdam, 1988, pp 125–141
Saddik M, Lopaschuk GD: Myocardial triglyceride turnover and contribution to energy substrate utilization in isolated working rat hearts. J Biol Chem 266: 8162–8170, 1991
Sardet, C, Counillon L, Franchi A, Pouyssegur J: Growth factors induce phosphorylation of a the Na+/H+ antiporter, a glycoprotein of 110 kD. Science 247: 723–725, 1990
Broderick TL, Quinney HA, Lopaschuk GD: Carnitine stimulation of glucose oxidation in the fatty acid perfused isolated working rat heart. J Biol Chem 267: 3658–3663, 1992
Lopaschuk GD, Wambolt RB, Barr RL: An imbalance between glycolysis and glucose oxidation is a possible explanation for the detrimental effects of high levels of fatty acids during aerobic reperfusion of ischemic hearts. J Pharmacol Exp Ther 264: 135–144, 1993
Krapf R, Pearce D, Lynch C, Xi XP, Reudelhuber TL, Pouyssegur J, Rector FC: Expression of rat renal Na/H antiporter mRNA levels in response to respiratory and metabolic acidosis. J Clin Invest 87: 747–751, 1991
Sardet C, Franchi A, Pouyssegur J: Molecular cloning, primary structure and expression of the human growth factor-activable Na+/H+ antiporter. Cell 56: 271–280, 1989
Biemesderfer D, Reilly RF, Exner M, Igarash P, Aronson PS: Immunocytochemical characterization of Na+-H+ exchanger isoform NHE-1 in rabbit kidney. Am J Physiol 263: F833–F840, 1992
Fliegel L, Haworth RS, Dyck JRB: Characterization of the placental brush border membrane Na+/H+ exchanger: Identification of thiol-dependent transitions in apparent molecular size. Biochem J 289: 101–107, 1993
Gotzsche O: Myocardial cell dysfunction in diabetes mellitus: A review of clinical and experimental studies. Diabetes 35: 1158–1162, 1986
Tahiliani AG, McNeill JH: Diabetes-induced abnormalities in the myocardium. Life Sci 38: 959–974, 1986
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Dyck, J.R., Lopaschuk, G.D. Glucose metabolism, H+ production and Na+/H+- exchanger mRNA levels in ischemic hearts from diabetic rats. Mol Cell Biochem 180, 85–93 (1998). https://doi.org/10.1023/A:1006891007014
Issue Date:
DOI: https://doi.org/10.1023/A:1006891007014