Contractility of Actomyosin Bands Prepared From Normal and Failing Human Hearts1

Abstract

Previous work from this laboratory has indicated that actomyosin bands prepared from heart muscle of dogs preserve undiminished contractility for one hour after the death of the animal (1). This suggested the possibility of investigating the contractile properties of actomyosin bands from human hearts obtained at autopsy. Such a study would make possible a comparison of actomyosin prepared from normal human heart muscle with that obtained from heart muscle of patients who had died of congestive heart failure. The method could also be used to obtain information on the effect of cardiac glycosides and other drugs on the contractile elements of normal and failing human heart muscle. To the present, only actomyosin preparations from hearts with artificially produced failure have been studied (2, 3). In these "models" obtained from dogs' hearts, the mechanism and nature of failure may vary from that encountered in man.The present report deals with a comparison of the contractile properties of actomyosin prepared from normal and failing human hearts and with the effect of calcium chloride and digoxin and the action of nicotine on these preparations. MATERIAL AND METHODSActomyosin solution was prepared in the cold (40 C.) as follows: The heart was minced with scissors and 10 Gm. supernatant fluid was again centrifuged at 4,000 rpm for 10 minutes. Following this, the supernatant fluid was diluted with a fivefold volume of triple glass distilled water; the pH was adjusted to 7.0 by careful addition of 1/10 N acetic acid. Usually, 17 ml. of the acid was sufficient. The solution was then centrifuged at 1,500 rpm for 30 minutes. The supernatant was discarded and the precipitate was suspended in about 20 ml. of triple glass distilled water and centrifuged again for 15 minutes. The precipitate was dissolved in 2 M KCl to a final concentration of 0.5 M KCl. One ml. of this solution was used for the formation of actomyosin bands. The solution was pipetted on the surface of a glass slide, from which it was transferred into a solution contained in a Langmuir trough. This trough solution contained 0.05 M KCl and 0.001 M magnesium chloride, and was buffered to a pH of 7.5 with 1/100 M barbital buffer. The temperature in the trough was kept at 240 C.The technique for the formation of bands has been previously described (4). However, since certain modifications were used, the method is briefly summarized at this point. The protein solution spread on the surface of the trough was compressed between two wooden sticks into bands, and then pushed gently into the contraction chamber containing 40 ml. of the trough solution (Figure 1). One end of the band was firmly fixed in position by a rigid connection with the bottom of the trough (Figure 1). The other end of the band was attached to the elongated arm of a Roller Smith torsion balance. The length of the band was approximately 2 cm., the width about 5 mm. Only afterloaded contractions were studied. The band was loaded by moving the weighing spring of the torsion balance by the desire...

Studies on Digitalis. Iv. Observations in Man on the Effects of Digitalis Preparations on the Contractility of the Non-Failing Heart and on Total Vascular Resistance

“…Furthermore, Olson recently reported that when the administration of digitoxin to dogs in experimental congestive heart failure resulted in clinical improvement, the abnormally elevated intrinsic viscosity of myosin which occurs in experimental heart failure was restored to normal; however, digitoxin did not alter the viscosity of the myosin of the non-failing heart (32). On the other hand, Kako (33).…”

High Energy Phosphate Compounds in the Myocardium during Experimental Congestive Heart Failure. Purine and Pyrimidine Nucleotides, Creatine, and Creatine Phosphate in Normal and in Failing Hearts*

“…Concentrations of high energy phosphates have been reported to be normal in isolated, acutely failing dog hearts, guinea pig atria, and cat papillary muscles (13)(14)(15) and in chronically failing hearts from dogs with tricuspid insufficiency and pulmonary stenosis or with aortic insufficiency ( 11,16). Muscle preparations from failing canine and human hearts have shown decreased contractility (17,18) and decreased ATPase activity (19), but myofibrillar proteins from failing canine hearts have been reported to be both normal (20) and altered (21).…”

A Lion at Rest

“…So, when he left cardiac metabolism disappointed because it did not reveal a clue to the cause of nonischemic heart failure, 16 he turned to ever more molecular questions: the contractility of actomyosin threads 17 and topics including protein metabolism in hypertrophy and failure, 18 coronary microcirculation, lipid metabolism in isolated perfused coronary arteries, experimental myocardial infarction, diltiazem, perfluorochemical emulsions as oxygen carriers, lysophosphatidylcholine and atherosclerosis, NO, eNOS, prostacyclin, iNOS, oxidation products of NO, cyclooxygenase inhibitors, and many others. He published his last original article as first author in 2001 at the age of 92, on NO, prostanoids, cyclooxygenase, and angiogenesis in colon and breast cancer.…”