Chronological effects of mild pressure overload on myosin ATPase activity in the canine right ventricle

152

This review has pointed out the good correlation frequently observed between ATPase activity of various contractile protein preparations and contractile function of various muscles including the myocardium. Some of the variables in the measurement of the various ATPases and the relationship of these measurements to physiological ATPase in the intact myofibril have been mentioned. The possible roles of changes in the light chains of sulfhydryl groups in the control of ATPase activity have been outlined. The possibility that phosphorylating reactions might exert control over physiological activity remains to be clarified. It is evident that, despite the large amount of research that has been done, our understanding of how the biochemistry of contractile proteins relates to physiological function is in its infancy, and only with a more complete elucidation of the underlying biochemistry of the components of contractile proteins of physiological and pathophysiological adaptations become evident.

Section: Myosin Structure and Function: The Role Of Light Chainsmentioning

confidence: 99%

Section: Myosin Structure and Function: The Role Of Light Chainsmentioning

confidence: 99%

Cardiac contractile proteins. Adenosine triphosphatase activity and physiological function.

Scheuer¹,

Bhan²

1979

152

“…It appears that the degree of elevation of ventricular pressure may be a determinant of whether myosin ATPase decreases or increases. In the canine pressure overload model examined by Wikman-Coffelt et al (1975), mild constriction of the pulmonary artery produced a 49% increase in heart:body weight ratio, and myosin ATPase was 35% above normal 5 weeks after surgery. This constriction causes a 60% increase in peak ventricular systolic pressure and no change in diastolic pressure.…”

Section: Comparison With Other Studies On Energetics Of Hypertrophymentioning

confidence: 99%

“…A second class of pressure overload models exhibits unchanged (Chandler et al, 1967) or increased myosin ATPase (Wikman-Coffelt et al, 1975). It appears that the degree of elevation of ventricular pressure may be a determinant of whether myosin ATPase decreases or increases.…”

Section: Comparison With Other Studies On Energetics Of Hypertrophymentioning

confidence: 99%

Increased myothermal economy of isometric force generation in compensated cardiac hypertrophy induced by pulmonary artery constriction in the rabbit. A characterization of heat liberation in normal and hypertrophied right ventricular papillary muscles.

Alpert¹,

Mulieri²

1982

246

SUMMARY. Initial, recovery, and resting heat were measured in normal and hypertrophied papillary muscles in order to monitor the energetic consequences of the subcellular changes accompanying hypertrophy. The pulmonary artery was constricted in rabbits 4 weeks prior to measurements. Right ventricular papillary muscles were stimulated at 0.2 Hz and 21 °C in Krebs-Ringer solution under isometric conditions at optimum length. Peak twitch tension was 5.90 ± 0.25 g/mm 2 (SEM) in normal muscle (N) and 5.11 ± 0.47 g/mm 2 (NS) in pressure overload muscle (P). The maximal rate of tension generation decreased 26% (P < 0.02) from 15.9 ± 0.85 g/mm 2 sec (N) to 11.7 ± 1.37 g/mm 2 sec (P). Time-to-peak tension increased 30% (P < 0.001) from 627 ± 20 msec (N) to 816 ± 21 msec (P). The total activity related heat production per beat decreased 36% (P < 0.001) from 3.92 ± 0.26 mcal/g (N) to 2.51 ± 0.29 mcal/g (P). Initial heat was reduced 37% (P < 0.001) from 1.66 ± 0.10 mcal/g (N) to 1.04 ± 0.12 mcal/g (P). The isometric heat coefficient increased 43% (P < 0.005) from 8.76 ± 0.54 (N) to 12.5 ± 1 (P) showing increased economy in hypertrophy. There was an early fast phase (1.29 ± 0.12 mcal/g per sec) of initial heat lasting 396 ± 25 msec which was related to tension build-up. A slow phase (1.05 ± 0.07 mcal/g per sec) accompanied relaxation. In hypertrophy, the fast phase was 32% (P < 0.05) slower than normal and lasted 27% (P < 0.02) longer; the slow phase was 48% (P < 0.001) slower than normal. The ratio of recovery to initial heat (1.37 ± 0.09) was not different in N and P muscles. Resting heat was 2.08 ± 0.35 mcal/g per beat in N and 1.35 ± 0.23 mcal/g per beat in P muscles. Our present results and previous enzymatic and mechanical studies suggest that the relation between the compensated pressure overload hypertrophied and normal hearts is similar to the relation between slow and fast skeletal muscle. The changes in the heart that undergoes hypertrophy secondary to pressure overload are beneficial, since they meet the new hemodynamic demands with increased economy of force production. (Circ Res 50: 491-500, 1982)THIS investigation was undertaken to provide in vivo monitoring of subcellular changes induced by pressure overload hypertrophy in rabbit heart. The deposited film thermopile that we recently developed (Mulieri et al., 1977) is ideally suited to this study, since its low thermal capacitance, high time resolution, and sensitivity allow temperature changes accompanying an individual twitch to be correlated with the simultaneously recorded myogram. This offers the possibility of monitoring the time course of initial and recovery heat in an individual twitch response and correlating these with the intracellular mechanical and enzymatic processes known to accompany different portions of the twitch myogram.In addition, it is also of interest to compare myothermically derived values of total isometric energy liberation with values derived from oxygen consumption determinations, since the latter measurements are not in agreeme...

“…A recent study reported elevated Ca 2+ -activated ATPase activity 3 weeks after pulmonary artery stenosis in dogs and this change was accompanied by a decreased ratio of light to heavy myosin chains. 41 The same group found that myosin ATPase activity, during hypertrophy, was related to whether stress was mild or severe and that decreased activity was accompanied by an increased ratio of light to heavy chains. 42 " 44 Katagiri and Morkin 45 found questionably depressed myosin ATPase and no change in the proportion of light to heavy chains in hypertrophy secondary to aortic coarctation in calves.…”

Section: Discussionmentioning

confidence: 98%

The amino acid composition of actin and myosin and Ca2+-activated myosin adenosine triphosphatase in chronic canine congestive heart failure.

Raszkowski¹,

Welty²,

Peterson³

1977

SUMMARY The Ca2+ -activated myosin ATPase and the amino acid compositions of actin and myosin were determined for preparations from chronically failing dog hearts. Hypertrophy and congestive heart failure were produced by combined tricuspid valve insufficiency and pulmonary artery stenosis. Control, shamoperated, and noncardiac circulatory failure (inferior vena cava constriction) dogs also were studied. All hearts were divided into right ventricle, septum, and left ventricle and each sample was individually analyzed. Calcium-activated ATPase decreased in the failing hearts and showed a distinct gradient of depression from right to left ventricles. There were no changes in ATPase activity among the other groups. The amino acid composition of actin was the same regardless of origin. The amino acid composition of myosin was unaltered except that cystine/2 residues were markedly decreased in failing heart myosin. The same gradient of depression was present as was found for Ca 2 -activated myosin ATPase. This study suggests that protein metabolism is abnormal and that altered proteins are produced in hypertrophy and congestive heart failure. It appears that these changes do not affect all proteins, since actin was normal by the parameters studied. It is clear that the stressed ventricle is the most severely involved, but the entire heart is altered to some degree. Thus, we conclude that altered protein metabolism may be an important primary factor in the genesis of heart failure.ALTHOUGH the contracility of hypertrophied and failing myocardium is decreased 1 " 3 the mechanism responsible for this alteration of physiological function is unknown. Structural abnormalities 4 and altered contractile and regulatory protein function 5 ' 6 have been demonstrated in the hypertrophied and failing heart and postulated to be causally related to the decreased contractile function. In particular, substantial evidence documenting altered activity of various adenosine triphosphatase (ATPase) systems isolated from failing or hypertrophied hearts or both has accumulated and suggests that an abnormality of energy release is responsible for the mechanical dysfunction.Although differences in sarcolemmal, 7 ' 8 sarcoplasmic reticulum, 7 ' 9 actomyosin, myosin, and myofibrillar ATPases have been reported, 5 the basis for these alterations remains obscure. This study was designed to evaluate the Ca 2+ -activated myosin ATPase in purified myosin from the chronically failing canine heart and to determine whether changes could be correlated with an alteration in the amino acid composition of myosin. Actin, the other major contractile protein of the heart responsible for the generation of tension, was also isolated from the same tissue sample and the amino acid composition was determined. MethodsAdult mongrel dogs of both sexes, weighing 15-30 kg, were kept and fed as previously described.7 Randomly selected dogs were trained to use a treadmill and were exercised for 2 weeks. Those with normal excise tolerance 10 were catheterized (right and ...