Decreased myocardial contractility in papillary muscles from atherosclerotic rabbits.

Abstract

To determine the effect atherosclerosis has on myocardial contractility, we studied the contractile properties of right ventricular papillary muscles from 34 atherosclerotic and 17 control rabbits. We produced atherosclerosis by feeding for 2 to 8 months a diet of 5% lard, 5% peanut oil, 0.5% cholesterol, and 89.5% rabbit pellets. The controls received only rabbit pellets during the same time interval. Contracting isometrically 12 times per minute at 25 degrees C, muscles from the atherosclerotic rabbits developed tension at a lower maximum rate (max dT/dt), had a longer latency, and required longer to develop tension at the maximum rate and to develop peak tension. In isotonic contractions, they shortened with lower maximum velocities and required longer to accelerate to maximum velocity and to shorten maximally. We found no evidence that developed tension or distance shortened differed between the two groups of muscles. Raising the contraction frequency to 24 contractions per minute between the two groups of muscles. Raising the contraction frequency to 24 contractions per minute brought performance of the two groups of muscles closer in both types of contraction. Norepinephrine (1.5 x 10-5 M) nearly abolished differences between performance of the two groups. The loss of contractility correlates poorly with coronary and aortic atherosclerosis. It occurred early in the feeding of the atherogenic diet. We think it was due to a lipid-induced defect in the cardiac cell's handling of calcium.

Influências de dietas ricas em ácidos graxos saturados e insaturados sobre o miocárdio de ratos

“…Although previous studies have shown that diet caused depressed cardiac function depression in isolated rabbit 12 and rat 13 papillary muscle, recent data from our laboratory 15 have shown that, in agreement with other authors 7,9,11,14 , UFA diet does not alter functional performance. On the other hand, there are few reports on the relationship between SFA rich diets and cardiac function.…”

“…Although literature shows that UFA rich diets cause morphometabolic alterations [6][7][8][9][10] , information is contradictory with respect to their effects on myocardium mechanical function 7,9,[11][12][13][14][15] . Although previous studies have shown that diet caused depressed cardiac function depression in isolated rabbit 12 and rat 13 papillary muscle, recent data from our laboratory 15 have shown that, in agreement with other authors 7,9,11,14 , UFA diet does not alter functional performance.…”

Downregulated myocardial connexin 43 and suppressed contractility in rabbits subjected to a cholesterol-enriched diet

“…11 The myocardial CVI, proven to be heart rate and load independent, could be considered as an index of intrinsic myocardial contractility. 14,33 According to the elastic modules model 13 and the microscopic elastic wave theory, 16 the size and interdistance of scatters (myocytes), the acoustic impedance mismatching between the myocytes' intracellular contents and the extracellular collagen networks, as well as the ultrasonic insonification angle, 34 determine the acoustic contrast responsible for the scattering and generate the CVI.…”

“…[5][6][7][8][9] Using chimeric mice created from Cx43-deficient stem cells and blastocysts, Gutstein et al 10 have demonstrated that spatially heterogeneous Cx43 downregulation is indeed linked to disturbances in electromechanical function in terms of both irregular epicardial conduction patterns and contractile dysfunction. 10 Dietary hypercholesterolemia has been also shown to induce contractile dysfunction independent of vascular disease, characterized by a decrease in the maximum rate of shortening and relaxation in a papillary muscle preparation, 11 although this finding has not been confirmed in isolated intact hearts. 12 Ultrasonic tissue characterization (UTC) with cardiac cycle-dependent variation of integrated backscatters (CVI) has been shown to be representation of intrinsic myocardial contractility and a potential indicator of early systolic dysfunction.…”

<a name="home"></a>Effect of unsaturated fatty acids on myocardial performance, metabolism and morphology

“…Some investigators have not detected shortening changes in isolated rat hearts (17) or left ventricle (LV) papillary muscle (1,18), while others have detected depressed mechanical function in isolated rabbit (19) and rat (20) LV papillary muscles.…”