Assay of myosin ATPase activity in cultured rat heart cells Paul McDermott, Monica Daood and Irwin Klein, University of Pittsburgh School of Medicine and the Pittsburgh Veteran's Administration Hospital, Pittsburgh, Pennsylvania

1983 ◽  
Vol 15 ◽  
pp. 33
Keyword(s):  
Atpase Activity ◽  
Rat Heart ◽  
Myosin Atpase ◽  
Heart Cells ◽  
University Of Pittsburgh ◽  
Myosin Atpase Activity ◽  
School Of Medicine ◽  
Administration Hospital ◽  
Rat Heart Cells ◽  
Pittsburgh School

Maximum heart rate of soricine shrews: correlation with contractile properties and myosin composition

1992 ◽  
Vol 262 (5) ◽  
pp. R842-R851 ◽  
Author(s):  
M. Vornanen
Keyword(s):  
Atpase Activity ◽  
Body Mass ◽  
Small Mammals ◽  
Rat Heart ◽  
Common Shrew ◽  
Electrophoretic Analysis ◽  
Myosin Atpase ◽  
Wild Mammals ◽  
Myosin Atpase Activity ◽  
The Common

Maximum heart rates (HR) of three soricine shrews and six other small mammals were measured in response to a single supramaximal dose of isoproterenol (Iso) under urethan anesthesia. The highest HR, 1,043 +/- 66 (SD) beats/min (n = 3), was in least shrew (Sorex minutus, mean body mass 3.02 +/- 0.81 g). Maximum HRs of common shrew (Sorex araneus, 7.16 +/- 1.54 g) and water shrew (Neomys fodiens, 12.80 +/- 1.54 g) were 938 +/- 29 (n = 7) and 887 +/- 21 (n = 6), respectively. In general, maximum HRs of soricine shrews and other small wild mammals followed the common mammalian pattern, fHmax/Iso = 443 x Mb-0.14, determined by body size. The exponent for this equation is smaller than that of resting HR (-0.25) (Stahl, J. Appl. Physiol. 22: 453-460, 1967), predicting crossover at approximately 3 g body mass. However, resting HRs of small mammals were clearly lower than expected on the basis of body mass. Lowering resting HR below the common mammalian level, with concomitant increase in stroke volume, seems to be a prerequisite for small mammals to regulate cardiac output against the ceiling of maximum HR. Electrophoretic analysis showed that the myosin of shrew ventricles is different from those of rodent species. In native conditions, shrew myosin, designated V1', migrated faster than the V3 and V1 forms of rat heart. On SDS gradient gel the single heavy chain of shrew myosin migrated slower than the alpha- or beta-chains of rat ventricle. Differences in the molecular weight of light chains were also noted between small mammals. Despite the notable differences in myosin composition, myosin-ATPase activity of the shrew hearts was similar to that of mouse and rat heart. Because duration of isometric contraction was inversely related to resting and maximum HRs, it was concluded that in the small mammals rate and duration of contraction are determined mainly by the release and uptake rate of myoplasmic Ca2+ and less by myosin-ATPase activity.

scholarly journals A comparative study of myosin and its subunits in adult and neonatal-rat hearts and in rat heart cells from young and old cultures

1980 ◽  
Vol 191 (2) ◽  
pp. 627-635 ◽  
Author(s):  
H A Ghanbari ◽  
R L McCarl
Keyword(s):  
Atpase Activity ◽  
Light Chain ◽  
Rat Heart ◽  
Neonatal Rat ◽  
Temperature Sensitive ◽  
Heart Cells ◽  
Subunit Structure ◽  
Dependent Atpase ◽  
Rat Hearts ◽  
Rat Heart Cells

A possible explanation for the decrease in myosin Ca2+-dependent ATPase activity as rat heart cells age in culture is presented. The subunit structure and enzyme kinetics of myosin from adult and neonatal rat hearts and from rat heart cells of young and old cultures are compared. These studies indicate that the loss in Ca-ATPase activity of myosin from older cultures was an intrinsic property of the myosin itself. Myofibrillar fractions from the indicated four sources showed no qualitative or quantitative differences in electrophoretic patterns. Myosin from older cultures was more sensitive to alkaline denaturation than was myosin from younger cultures, as indicated by its more accelerated loss of K+(EDTA)-dependent ATPase activity after 10 min of incubation at pH 10. Furthermore, myosin from older cultures was more temperature-sensitive, as indicted by a more rapid loss of Ca-ATPase with decrease in assay temperature. It is suggested that there is either a change in conformation of myosin molecules at or near the active site of the enzyme or alternatively there is a change in light chain 1-light chain 2 and/or light-chain-heavy-chain interaction(s) in the myosin molecules under study.

Ouabain treatment of cardiac cells induces enhanced Na+-Ca2+ exchange activity

1989 ◽  
Vol 256 (6) ◽  
pp. C1273-C1276 ◽  
Author(s):  
R. Vemuri ◽  
S. Longoni ◽  
K. D. Philipson
Keyword(s):  
Atpase Activity ◽  
Rat Heart ◽  
Cardiac Glycosides ◽  
Cardiac Cells ◽  
Neonatal Rat ◽  
Heart Cells ◽  
Subsequent Increase ◽  
Neonatal Rat Heart ◽  
Rat Heart Cells ◽  
Exchange Activity

Inhibition of the cardiac Na+-K+-ATPase with cardiac glycosides causes a rise in internal Na+ and a subsequent increase in cellular Ca2+ due to the sarcolemmal Na+-Ca2+ exchange mechanism. We investigated the adaptation of cultured cardiac cells to prolonged elevation of internal Ca2+ after exposure to ouabain. Cultured neonatal rat heart cells were treated with 100 microM ouabain for 4-48 h. This ouabain concentration inhibited Na+-K+-ATPase activity by approximately 45% and caused modest cellular Ca2+ loading. We found that cells adapted to ouabain treatment by increasing the amount of sarcolemmal Na+-Ca2+ exchange activity by 50-90% over a 24-h period. Kinetic and immunological data indicate that the increase was due to increased numbers of functional exchangers. Neither total cellular nor total sarcolemmal protein content was affected by the ouabain treatment. These results may be relevant toward understanding the effects of therapeutic use of cardiac glycosides.

Postgraduate Course on Diseases Due to Immune Mechanisms

PEDIATRICS ◽  
1965 ◽  
Vol 35 (3) ◽  
pp. 508-511
Keyword(s):  
Clinical Immunology ◽  
The United States ◽  
Associate Professor ◽  
Veterans Administration ◽  
University Of Pittsburgh ◽  
School Of Medicine ◽  
Administration Hospital ◽  
The University ◽  
Pittsburgh School ◽  
Comprehensive Discussion

The University of Pittsburgh School of Medicine in co-operation with The Veterans Administation Hospital, announces a course to be given May 17-21, 1965, in which a distinguished faculty from many areas of the United States will guide a comprehensive discussion of modern concepts of immunologic mechanisms. Special attention will be devoted to agammaglobulinemia, autoimmunity, transplantation phenomena, and selected aspects of clinical allergy. Enrollment is limited. Inquiries should be addressed to: Leo H. Criep, M.D., Clinical Associate Professor of Medicine, Clinical Immunology Laboratory, Veterans Administration Hospital, Pittsburgh, Pennsylvania 15240.

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