| Influence of Hypertonic Solution on Myocardial Contractility . |
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Wha Sung Chung |
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Department of Anesthesiology, Yonsei University School of Medicine, Seoul, Korea. |
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| Abstract |
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The influences of osmolarity on the cardiac muscle contraction were investigated in cat papillary muscles. The muscle was immersed in the modified Krebs-Ringer-bicarbonate solutions containing various Ca ion concentrations and osmolarities and the resultant changes in maximum developed tension, rate of development of tension and time to maximum tension were analyzed. Following are the results. 1) Mean length of papillary muscle used was 9.3+/-0.60mm, end mean cross-sectional area was l. 73+/-0.07 mm2. Normal contraction amplitude at 5 mM Ca ion-K-R-B solution was 2.
46+/-0. 1 gram/mm. 2) Within the range of 2.5-10.0 mM Ca ion concentration, the contraction amplitude increased along with the increment of Ca concentration. 3) Osmolarity exerted dual effects on contraction; within the range of 300-400 mosm/I solution, the hypertonic solution exported a positive inotropic effect while 500 mOsm/1 solution exerted a negative inotropic effect upon papillary muscle. 4) Maximum rate of tension development increased in 350 mOsm/1 solution, but decreased in 400 mOsm/1 or more hypertonic solution. The time to maximum tension did not change within the range of 300 400 mOsm/1 osmolarity and in 500 mOsm/1 solution. 5) The difference in maxium developed tension between single and paired stimulation was 1. 99 gram/mm' at 300 mOsm/1 solution and was negligible in 450 mOsm/1 or more hypertonic solutions. |
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