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|Type:||Artigo de periódico|
|Title:||Contribution Of Ca2+ Transporters To Relaxation In Intact Ventricular Myocytes From Developing Rats|
|Abstract:||The relative contributions of Ca2+ transporters to intracellular Ca2+ concentration ([Ca2+]i) decline associated with twitch relaxation were analyzed in intact ventricular myocytes from developing and adult rats. This was accomplished by estimation of individual integrated Ca2+ fluxes with the use of kinetic parameters calculated from [Ca2+]i measurements during twitches and caffeine-evoked contractures, and from myocardial passive Ca2+ buffering data. Our main findings were the following: 1) twitch relaxation and [Ca2+]i decline were significantly slower during the first postnatal week than in adults, 2) inhibition of sarcoplasmic reticulum (SR) Ca2+ accumulation resulted in faster [Ca2+]i decline in young cells than in adult cells, 3) the contributions of the SR Ca2+ uptake and Na+/ Ca2+ exchange (NCX) to twitch relaxation increased from ∼75 to 92%, and decreased from 24 to 5%, respectively, from birth to adulthood, and 4) Ca2+ transport by the sarcolemmal Ca2+ -ATPase was apparently increased in neonates. Our data indicate that despite a marked increase in NCX contribution to cell relaxation in immature rats, the SR Ca2+-ATPase appears to be the predominant transporter responsible for relaxation-associated [Ca2+]i decline from birth to adulthood.|
|Appears in Collections:||Unicamp - Artigos e Outros Documentos|
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