Recent advances in studies on cardiac structure and metabolism最新文献

We have studied the incorporation of various long chain fatty acids into tissue lipids using various heart preparations. We found that individual fatty acids are incorporated into various lipid fractions at unequal rates. In particular, erucic acid was shown to be a poor acyl donor for various acylation reactions. Labeling of triacylglycerol by exogenous fatty acid was found to be extremely rapid in the perfused rat heart and in the in vivo heart.

Canine cardiac myosin, which was synthesized in a 14-day tissue culture, based on L-[3H] leucine incorporation, was precipitated with goat gamma G antimyosin (cardiac-specific) and analyzed on dodecylsulfate gels. Incorporation of 32PO4 into myosin chains occurring in culture was the same as that obtained in vivo and appeared to be coupled with translation. Removal of 32PO4 from myosin heavy chains with base treatment indicated the presence of phosphoserine and phosphothreonine in canine cardiac myosin heavy chains. Further acid hydrolysis confirmed the data. The system described here, i.e., analyses of 32PO4 and L[3H] leucine incorporation into myosin heavy chains, could be used as a system for assaying hypertrophying factors.

The data obtained from groups of young and old beagles demonstrate that senescent beagle hearts are characterized by lower contractile function as measured by developed pressure and maximal rate of pressure change with time, by longer contraction duration, and by increased dynamic stiffness per given pressure as measured by the sinusoidal forcing technique.

Myocardial protection by means of selective, continuous coronary perfusion with cold oxygenated blood of low flow rate and of low perfusion pressure is an excellent procedure both clinically and experimentally. This method should be particularly useful in poor-risk patients, for whom a maximal preservation of the myocardium is imperative.

A directional nonuniformity of the intramyocardial pressure (IMP) was observed in anesthetized open-chest dogs using a piezoelectric pressure sensor implanted in the left ventricular myocardium. The nonuniformity seemed to be attributable to the variation in myocardial fiber orientation. The IMP, which developed in a direction parallel to the base-apex line, was measured in the deep portion of the myocardium, simultaneously with local O2 availability. In some cases, IMP decreased quickly as soon as a decrement in O2 availability had proceeded only slightly as a result of ligation of the anterior descending artery (LAD). In other cases, the once decreased IMP recovered gradually even when O2 availability remained lowered by continuation of the ligation. These observations indicated that IMP had no direct dependency on O2 availability in the case of acute LAD.

The moles of calcium bound by the left ventricle were 1.5 +/- 0.1, while those of the right ventricle were 2.9 +/- 0.2. The calcium binding constants were the same between myosins of the two cardiac ventricles. The Ca2+ binding constants were approximately 1.1 X 10(5) M-1 for both left and right ventricular myosins. Left ventricular myosin bound 1.3 +/- 0.1 mol of Mn2+, whereas right ventricular myosin bound 2.8 +/- 0.1 mol of Mn2+. The divalent cation Mn2+ only partially competed out Ca2+ (50%). Because of the partial competition, it seemed that Ca2+ and Mn2+ had some sights in common. These studies demonstrate a twofold difference in divalent cation binding (Ca2+, Mn2+) between left and right ventricular myosins. This variation in cation binding between the two ventricles is reflected in similar differences in myosin ATPase activity between the two ventricles.

The effect of acetaldehyde, the hepatic metabolite of alcohol, on the functioning of cardiac muscle was investigated at the subcellular level. Concentrations of acetaldehyde that occur in plasma failed to alter either the microsomal Ca2+-accumulating and ATPase activity or the Ca2+-accumulating activity of the mitochondria. These same concentrations of acetaldehyde inhibited the Ca2+-dependent myofibrillar ATPase.

The formation of free radicals, which was represented by the concentration of free radicals in state 4 respiration, and the respiratory control ratio were studied in the myocardial mitochondria isolated from dog hearts that were failing due to aortic constriction. Both formation and respiratory control ratio were lowered, compared to each control value, in acute and chronic heart failure. A positive correlation was recognized between free radicals in state 4 respiration and respiratory control ratio. From these results it was concluded that there was uncoupling of oxidative phosphorylation in the mitochondria isolated from failing dog hearts. Measurement of free radicals in state 4 respiration, as well as respiratory control ratio, is a useful method for evaluation of the function of oxidative phosphorylation.