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Type: Artigo de periódico
Title: Osmolality- And Na+ -dependent Effects Of Hyperosmotic Nacl Solution On Contractile Activity And Ca2+ Cycling In Rat Ventricular Myocytes.
Author: Ricardo, Rafael A
Bassani, Rosana A
Bassani, José W M
Abstract: Hypertonic NaCl solutions have been used for small-volume resuscitation from hypovolemic shock. We sought to identify osmolality- and Na(+)-dependent components of the effects of the hyperosmotic NaCl solution (85 mOsm/kg increment) on contraction and cytosolic Ca(2+) concentration ([Ca(2+)](i)) in isolated rat ventricular myocytes. The biphasic change in contraction and Ca(2+) transient amplitude (decrease followed by recovery) was accompanied by qualitatively similar changes in sarcoplasmic reticulum (SR) Ca(2+) content and fractional release and was mimicked by isosmotic, equimolar increase in extracellular [Na(+)] ([Na(+)](o)). Raising osmolality with sucrose, however, augmented systolic [Ca(2+)](i) monotonically without change in SR parameters and markedly decreased contraction amplitude and diastolic cell length. Functional SR inhibition with thapsigargin abolished hyperosmolality effects on [Ca(2+)](i). After 15-min perfusion, both hyperosmotic solutions slowed mechanical relaxation during twitches and [Ca(2+)](i) decline during caffeine-evoked transients, raised diastolic and systolic [Ca(2+)](i), and depressed systolic contractile activity. These effects were greater with sucrose solution, and were not observed after isosmotic [Na(+)](o) increase. We conclude that under the present experimental conditions, transmembrane Na(+) redistribution apparently plays an important role in determining changes in SR Ca(2+) mobilization, which markedly affect contractile response to hyperosmotic NaCl solutions and attenuate the osmotically induced depression of contractile activity.
Subject: Animals
Calcium Signaling
Cardiotonic Agents
Cell Size
Enzyme Inhibitors
Myocardial Contraction
Myocytes, Cardiac
Osmolar Concentration
Rats, Wistar
Saline Solution, Hypertonic
Sarcoplasmic Reticulum
Sarcoplasmic Reticulum Calcium-transporting Atpases
Time Factors
Rights: fechado
Identifier DOI: 10.1007/s00424-007-0322-3
Date Issue: 2008
Appears in Collections:Unicamp - Artigos e Outros Documentos

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