Effects of Gd3+ and Ca2+ on Frog Heart Muscle Contractility and Respiration, Swelling and Inner Membrane Potential of Rat Heart Mitochondria

Abstract

We studied the inotropic and chronotropic effects of gadolinium ions (Gd3+) on contractility of frog Rana ridibunda heart muscle preparations. In addition, the influence of Gd3+ on oxygen uptake rates, swelling and the mitochondrial inner membrane potential (ΔΨmito) were studied in glutamate- and malate-energized rat heart mitochondria (RHM). It was found that Gd3+ decreases the amplitude and frequency of spontaneous heart contractions. At the same time, Gd3+ prevents Ca2+-induced swelling of these organelles in saline media and falling of ΔΨmito. In this case, regardless of the presence of Ca2+ in the medium, Gd3+ has a weak effect on mitochondrial state 3 or 3UDNP respiration (in the presence of 2,4-dinitrophenol). In calcium free experiments, Gd3+ stimulates passive swelling of RHM. These effects of Gd3+ may indicate that Gd3+ has no toxic effect on RHM but, on the other hand, inhibits opening of the mitochondrial permeability transition pore (MPTP) in the inner membrane. Our data provide better insight into the mechanisms of action of rare earth elements on Ca2+-dependent processes in the myocardium of vertebrates.