EFFECTS OF CESIUM ON SPONTANEOUS RATE IN RIGHT ATRIA ISOLATED FROM DIABETIC RATS

Previous studies have shown that streptozotocin (STZ) induced diabetes in rats is associated with a decrease in the spontaneous rate of isol ated right atria. Present experiments were designed to determine wheth er this model of insulin-dependent diabetes mellitus alters the chrono tropic actions of cesium (Cs+). Right atrial preparations were isolate d from STZ-treated and diluent-treated control rats, and bathed in Kre bs-Henseleit buffer at 37 degrees C; dose-dependent (0.2 - 10 mM) effe cts of Cs+ were examined by cumulative addition. Preparations isolated from diabetic rats had a slower beating rate before exposure to Cs+, and the negative chronotropic response to this cation was diminished i n these tissues. In fact, at concentrations between 2 and 10 mM Cs+, s pontaneous rate did not differ between the diabetic and control groups . These data suggest that the hyperpolarization-activated current, I-f , may play a role in the slower spontaneous pacemaker rate observed in right atria isolated from STZ-induced diabetic rats.