[Effect of nitric oxide on force-frequency relations in experimental hyperfunction and hypertrophy in the heart...

The influence of nitric oxide--NO on force-frequency relations in normal and hypertrophy rats isolated papillary muscles were compared using isometric force measurement. Stimulation frequency varied between 0.33 and 3 Hz. In normal conditions rat papillary muscle exhibit a negative force-frequency staircase, which is different from hypertrophy ventricular preparations (force-frequency relations practically be absent). During the incubation of hypertrophy ventricular preparations in nitro-glycerinem-containing solution (NO donator) the force-frequency relations measured on these muscles display the same behaviour as in normal conditions. The application of a caffeine into the bath solution abolishes a negative force-frequency staircase in all bunches of experiments. Under durable infusion of NO-predecessor--L-arginine to the rats (100 mg/kg) with hypertrophy of heart, the papillary muscle exhibits a positive force-frequency staircase. Caffeine did not caused any changes in force-frequency relations on rats ventricular preparations in there conditions. We conclude that the paradoxical response of hypertrophy of hearts is connected to infringements of redistribution of ions Ca between extracellular medium and intracellular stores in a systole and diastole.