Effects of Some Metabolic Influences on the Spontaneous Activity of Cultured Rat Heart Cells

Abstract

Summary

The effects of 2-deoxy-D-glucose (2-DG) were studied on postnatal rat heart cultures in Hanks' balanced salt solution. In this medium, the cardiac cells maintained a stable rhythm for a prolonged period of time. When glucose was the substrate, 2-DG depressed the rate of beating; this depression was reversed by ATP or pyruvate. ATP also stimulated the rate in cells without 2-DG, whereas pyruvate had no effect. Intracellular ATP levels were decreased by 2-DG, and incubation with pyruvate increased the ATP levels both in treated and untreated cultures. In the absence of glucose, the rate of beating remained unchanged, but addition of 2-DG stopped the beating, whereas glucose was only partially effective in counteracting the 2-DG depression. However, pyruvate and glucose, whatever the order of addition, restored the rate. Electrical stimulation induced beating in cultures treated with 2-DG and pyruvate or ATP in glucose-free medium. These findings indicate that, although the energy derived from the Krebs cycle is of importance for supporting contractility, adequate glucose utilization is needed for automatism in cardiac cells.