Properties of ventricular myocytes isolated from the hypertrophied and failing hearts of spontaneously hypertensive rats.

Objective: To investigate how the morphological and physiological properties of single myocytes isolated from the hypertrophied, failing left ventricles (LV) differ from those of normal or hypertrophied not failing ventricles.

Method: Single myocytes were isolated separately from right (RV) and left ventricles (LV) of male spontaneously hypertensive rats (SHR) or Wistar-Kyoto (WKY) rats at the age of 6 and 12 months and of SHRs which developed or not developed heart failure at the age of 20-24 months. We measured cells dimensions, range and kinetics of electrically stimulated or initiated by caffeine contractions and Ca2+ transients, and investigated the response of cells to thapsigargin.

Effects of mibefradil, a blocker of T-type Ca2+ channels, in single myocytes and intact muscle of guinea-pig heart.

We investigated the effects of a relatively selective blocker of the T-type Ca2+ channels, mibefradil (MBF), in the isovolumic left ventricles of the isolated, perfused hearts of guinea-pigs and single myocytes isolated from the ventricles of this species. In the myocytes superfused with 0 Na+ solution containing 200 microM lidocaine and pulsed from -90 mV to -40 mV to +5 mV, MBF proved to be about 3 times more potent inhibitor of the T-type than of the L-type Ca2+ current. The effect on the L-type current was strongly voltage and use dependent.

Effects of in vivo vanadate administration on calcium exchange and contractile force of rat ventricular myocardium.

The aim of this study was to evaluate the effect of a 14-day intragastric administration of Na3VO4 (0.03 mmol/kg daily) on calcium metabolism and contractile force of rat myocardium. Left ventricular pressure as well as its first derivative (dP/dt) were registered with a balloon inserted to this ventricle and the cellular content of exchangeable calcium with the aid of 45Ca2+.

Effects of in vivo manganese administration on calcium exchange and contractile force of rat ventricular myocardium.

The purpose of this study was to investigate the effect of prolonged (14 days) intragastric administration of Mn2+ (0.25 mmol/kg daily) on Ca2+ exchange and contractility of rat ventricular myocardium. Left-ventricular pressure and its first derivative (dP/dt) were recorded by means of a balloon catheter inserted via the left atrium into the left ventricle of the rat heart perfused by Langendorff method.

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.