Exogenous Calcium Preconditions Myocardium from Patients Taking Oral Sulfonylurea Agents

Abstract

We have previously reported that atrial trabeculae from patients taking oral sulfonylurea hypoglycemic agents cannot be preconditioned by transient ischemia, which may, in part, explain the increased cardiovascular mortality historically associated with the use of these agents (J. C. Cleveland et al., 1997, Circulation 96, 29–32). Recently, we reported that clinically accessible and acceptable exogenous Ca2+ pretreatment protects human atrial trabeculae from subsequent ischemia (B. S. Cain et al., 1998, Ann. Thoracic Surg. 65, 1065–1070). It remains unknown whether this preconditioning strategy could confer protection to trabeculae from patients taking oral sulfonylurea drugs. We therefore hypothesized that exogenous Ca2+ confers ischemic protection to trabeculae from patients taking oral sulfonylureas. Human atrial trabeculae were suspended in organ baths and field stimulated at 1 Hz, and force development was recorded. Following 90 min equilibration, trabeculae from patients taking oral sulfonylurea agents (n = 6 patients) were subjected to ischemia/reperfusion (I/R; 45/120 min) with or without Ca2+ (1 mM increase × 5 min) 10 min prior to I/R. I/R decreased postischemic human myocardial contractility in trabeculae from patients on oral hypoglycemics to 15.3 ± 2.0% baseline developed force (%BDF). Ca2+ pretreatment increased postischemic human myocardial developed force to 35.3 ± 2.9 %BDF in these patients (P < 0.05 vs I/R, ANOVA and Bonferroni/Dunn). We conclude that atrial muscle from patients taking oral hypoglycemic agents can be preconditioned with exogenous Ca2+. This therapy may offer a clinically relevant means to precondition the myocardium of diabetics taking oral hypoglycemic agents prior to clinical interventions such as coronary angioplasty or cardiac bypass.