Combined therapy with dimethylthiourea, diltiazem and amiloride/dimethylamiloride in the ischemic/reperfused heart.

Objectives: The relative contribution of oxygen free radicals, disturbances in calcium homeostasis and Na+/H+ exchange in the development of injury in the ischemic/reperfused heart was investigated. The study was designed to assess whether these factors initiate independent mechanisms of injury or, alternatively, they share a common mechanism of toxicity.

Methods: Isolated working rat hearts were subjected to different periods (30-55 min) of global ischemia and then were reperfused for 30 min.

Activation of pyruvate dehydrogenase by electrical stimulation, and low-Na+ perfusion of guinea-pig heart.

(1) Electrical stimulation (2 Hz) of guinea-pig hearts, perfused with medium containing 11 mM D-glucose plus 0.1 mM octanoate as substrate, resulted in an increase in the percentage of pyruvate dehydrogenase in the active form (PDHa) from 16 to 68%. (2) Rapid isolation of mitochondria by a technique designed to minimize net loss or gain of Ca2+ revealed an increase in mitochondrial Ca2+ content of the stimulated hearts, as measured with 45Ca (2.

Interaction between the sarcoplasmic reticulum and mitochondria in the control of contractile calcium in guinea-pig atria--does it exist?

The inhibitory action of caffeine on calcium (Ca2+) release from the sarcoplasmic reticulum (SR) and interference with mitochondrial (Ca2+) fluxes by a mitochondrial uncoupler protonfore CCCP were utilized to define a calcium pool responsible for potentiation of post-rest twitch tension in guinea-pig atria. The Ca2+ fluxes were assessed by means of 45Ca2+. Caffeine and CCCP when applied separately did not affect post-rat 45Ca2+ content.

Effect of inhibitors of slow calcium current on resting calcium efflux from cat papillary muscles.

Examination of influence of divalent cations (Co2+, Ni2+, Mn2+) and organic blockers (verapamil and D600) on calcium efflux from resting mammalian myocardium shows that they either inhibit or increase transiently 45Ca2+ efflux, depending on the site of action. It seems that those agents whose sites of action are limited to the sarcolemma inhibit Ca2+ efflux. Co2+, Ni2+, verapamil and D600 belong to this group.

Calcium shifts accompanying rest-dependent phenomena in atrial muscle of guinea-pig heart.

Calcium shifts accompanying rest and post-rest phenomena in isolated left atrial appendages of guinea-pig heart were investigated by means of isotope 45Ca2+. Experiments were performed under conditions of full equilibration of preparations with isotope-containing solution (at least 45 min) in order to investigate the changes in content of exchangeable Ca, or at short exposure to isotope (2-5 min) in order to measure the excitation-dependent Ca2+ influx. Atria stimulated at the rate of 60/min for 55 min in radioactive solution contained 3.