Study of the characteristics of the inotropic effect of insulin in rabbit papillary muscle.

The effect of insulin was examined with emphasis on the alteration in the force-frequency relation. The results show that insulin does not change the time to peak tension nor the time of contraction. The inotropic effect was significant and did not depend upon the frequency of stimulation. However, there was a definite dependence of the magnitude of the inotropic effect on temperature. Previous studies have indicated that the inotropic effect is not a result of increased substrate availability or changes in cAMP phosphodiesterase activity. These results and those reported here are consistant with the hypothesis that insulin's inotropic effect is due to increases in intracellular Ca++.     

The effect of quinidinebis-(7-theophylline acetate) on the isolated papillary muscle of the rabbit heart

Zusammenfassung Untersuchungen über die Aktion des Chinidinbis-(7-theophyllin acetat) auf den isolierten Pappilarmuskel beweisen, dass die Substanz die Verlängerung der Repolarisation, der Refraktärphase, als auch der Kontraktionsdauer bewirkt. Amplitude des Ruhe- und Aktionspotentials, Verlauf der Depolarization und die Kontraktionskraft bleiben praktisch unbeeinflusst.     

The effect of various anions on the contractility of the guinea-pig papillary muscle

Zusammenfassung Ersatz der Chlorionen des Suspensionsmediums durch NO ₃ ^– , Br^– oder J^–verstärkt die Kontraktionskraft des Herzmuskels im Gegensatz zu der des Skelettmuskels durch Vergrösserung der Anstiegssteilheit der Kontraktion. Dagegen wirkt F^– (5 mM) am Herzen positiv inotrop durch Verlängerung der Anstiegszeit der Kontraktion.     

Cardiac muscle: Changes in optimal length during inotropic interventions

Résumé Des courbes exprimant le rapport longueurtension dans le muscle papillaire du chat furent étudiées en comparant des changements successifs de longueur. En traitant la préparation avec des substances inotropes, on produisit souvent des modifications marquées de la longueur optimale. Ces modifications peuvent avoir une importance dans la relation volume-pression du cur intact.

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This investigation was supported in part by a grant-in-aid from the American Heart Association, USPHS Research Grant No. HE 10282 from the National Heart Institute and a USPHS General Research Support Grant.     

The role of calcium in the negative inotropic effect of lanthanum

Summary Lanthanum reduces the rate of calcium fast exchanging processes, whereas the slowly exchanging phase is not modified. Experimental data also confirm the importance of calcium fast exchanging fraction in regulating contractile force of cardiac muscle.     

Papaverine enhances the negative inotropic effect of acetylcholine in rat auricles

Summary The negative inotropic effect of acetylcholine in rat left auricles is enhanced in the presence of the phosphodiesterase inhibitor papaverine. This result favours the idea of a cyclic GMP-mediated action of acetylcholine in the heart.I thank Lydia Paragnik for help. This research was supported by a grant from the Deutsche Forschungsgemeinschaft.     

A negative inotropic effect of acetylcholine in the presence of several phosphodiesterase inhibitors

The phosphodiesterase inhibitors papaverine, theophylline and 3-isobutyl-1-methylxanthine (IBMX) reveal a negative inotropic effect of acetylcholine in cat ventricular heart muscle. This effect in unrelated to beta-adrenoceptor stimulation and possibly mediated by the accumulation of cyclic GMP.     

A negative inotropic effect of acetylcholine in the presence of several phosphodiesterase inhibitors

Summary The phosphodiesterase inhibitors papaverine, theophylline and 3-isobutyl-1-methylxanthine (IBMX) reveal a negative inotropic effect of acetylcholine in cat ventricular heart muscle. This effect is unrelated to -adrenoceptor stimulation and possibly mediated by the accumulation of cyclic GMP.I thank Mrs Petra Lauck for help. This work was supported by the Deutsche Forschungsgemeinschaft.     

Effect of platelet activating factor on guinea-pig papillary muscle

Summary Platelet activating factor (PAF) induces a biphasic effect on guinea-pig papillary muscle: 1. a transient positive inotropic effect preceded by an increase in action potential duration (APD); 2. a marked negative effect on inotropism and on APD. Since Ca⁺⁺ slow action potentials were initially enhanced by PAF and then markedly depressed, it is suggested that PAF specifically interferes with the Ca⁺⁺ slow channel.     

Effect of platelet activating factor on guinea-pig papillary muscle

Platelet activating factor (PAF) induces a biphasic effect on guinea-pig papillary muscle: 1. a transient positive inotropic effect preceded by an increase in action potential duration (APD); 2. a marked negative effect on inotropism and on APD. Since Ca++ slow action potentials were initially enhanced by PAF and then markedly depressed, it is suggested that PAF specifically interferes with the Ca++ slow channel.     

Effect of substrates on the mechanical performance of rhesus monkey papillary muscle

This study examines the effect of different substrates on mechanical performance of excised papillary muscles from rhesus monkeys which had been divided into a control group and an experimental group fed a high fat diet for 5 months prior to sacrifice. The results show that performance is affected by availabel substrate for both groups. The performance of the experimental group was depressed relative to control with the short chain fatty acid, butyrate (C4), producing a monotonically decreasing force-frequency response. Relative to the other mammals, isolated rhesus papillary muscles exhibited a protracted treppe which was sensitive to beta-adrenergic blockade with propranolol.     

Effect of substrates on the mechanical performance of rhesus monkey papillary muscle

Summary This study examines the effect of different substrates on mechanical performance of excised papillary muscles from rhesus monkeys which had been divided into a control group and an experimental group fed a high fat diet for 5 months prior to sacrifice. The results show that performance is affected by available substrate for both groups. The performance of the experimental group was depressed relative to control with the short chain fatty acid, butyrate (C4), producing a monotonically decreasing force-frequency response. Relative to other mammals, isolated rhesus papillary muscles exhibited a protracted treppe which was sensitive to -adrenergic blockade with propranolol.Acknowledgments. I would like to thank Dr R.M. Larson, Dr R.L. McCann and Dr O.F. Hagan for making available the papillary muscles used in this study. Support for this work was provided in part by a grant from the Walker P. Inman Fund and grants from the NIH HL 17391 and HL 15448.