Characteristics of Na⁺‐Ca²⁺ exchange in frog skeletal muscle
1. Fluxes studies were carried out to investigate the Na⁺-dependent outward movement of Ca²⁺ in intact frog sartorius muscle from <i>Leptodactylus ocellatus</i>, a preparation for which published data on the subject are sparse. 2. Under normal resting conditions the Na⁺-Ca²⁺ exchange wa...
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Formato: | Articulo |
Lenguaje: | Inglés |
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1995
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Acceso en línea: | http://sedici.unlp.edu.ar/handle/10915/123160 |
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I19-R120-10915-123160 |
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institution |
Universidad Nacional de La Plata |
institution_str |
I-19 |
repository_str |
R-120 |
collection |
SEDICI (UNLP) |
language |
Inglés |
topic |
Medicina Frog skeletal muscle Caffeine Medicinal chemistry Na+-Ca2+ exchange |
spellingShingle |
Medicina Frog skeletal muscle Caffeine Medicinal chemistry Na+-Ca2+ exchange Hoya, Arturo Venosa, Roque Alberto Characteristics of Na⁺‐Ca²⁺ exchange in frog skeletal muscle |
topic_facet |
Medicina Frog skeletal muscle Caffeine Medicinal chemistry Na+-Ca2+ exchange |
description |
1. Fluxes studies were carried out to investigate the Na⁺-dependent outward movement of Ca²⁺ in intact frog sartorius muscle from <i>Leptodactylus ocellatus</i>, a preparation for which published data on the subject are sparse.
2. Under normal resting conditions the Na⁺-Ca²⁺ exchange was not readily detectable.
3. When muscles were exposed to 4 mM caffeine, the rate of fractional loss of Ca²⁺ (k<sub>Ca,o</sub>) increased by about 50%. Most of this increase exhibits characteristics typical of the Na⁺-Ca²⁺ antiport working in the forward mode found in other cells.
4. The increase in k<sub>Ca,o</sub> promoted by caffeine was decreased by: (a) 72% in the absence of external Na⁺ (Na⁺<sub>o</sub>); (b) 73% in Na⁺-loaded muscles ([Na⁺]<sub>i</sub> = 98 mM); (c) 70% when fibres were depolarized to -27 mV ([K⁺]<sub>o</sub> = 50 mM); and (d) 80% in the presence of 5 mM amiloride.
5. Ni²⁺ (5 mM), an inhibitor of the Na⁺-Ca²⁺ exchanger current, unexpectedly increased the caffeine-promoted rise in k<sub>Ca,o</sub>. This effect of Ni²⁺ was associated with a concomitant caffeine-stimulated Ni²⁺ influx. In the absence of caffeine Ni²⁺ did not affect k<sub>Ca,o</sub>.
6. It was concluded that: (a) under resting conditions the sarcolemmal Ca²⁺ pump suffices to handle the cytosolic calcium concentration ([Ca²⁺]<sub>i</sub>); (b) Na⁺-Ca²⁺ activity becomes apparent when [Ca²⁺]<sub>i</sub> is substantially increased by caffeine-induced Ca²⁺ release from the sarcoplasmic reticulum; and (c) the blocking effect of Ni²⁺ on the current generated by a Na⁺-Ca²⁺ exchange with a coupling ratio > 2 might actually represent a shift of the antiport mode toward an electroneutral 1Ni²⁺-1Ca²⁺ exchange. |
format |
Articulo Articulo |
author |
Hoya, Arturo Venosa, Roque Alberto |
author_facet |
Hoya, Arturo Venosa, Roque Alberto |
author_sort |
Hoya, Arturo |
title |
Characteristics of Na⁺‐Ca²⁺ exchange in frog skeletal muscle |
title_short |
Characteristics of Na⁺‐Ca²⁺ exchange in frog skeletal muscle |
title_full |
Characteristics of Na⁺‐Ca²⁺ exchange in frog skeletal muscle |
title_fullStr |
Characteristics of Na⁺‐Ca²⁺ exchange in frog skeletal muscle |
title_full_unstemmed |
Characteristics of Na⁺‐Ca²⁺ exchange in frog skeletal muscle |
title_sort |
characteristics of na⁺‐ca²⁺ exchange in frog skeletal muscle |
publishDate |
1995 |
url |
http://sedici.unlp.edu.ar/handle/10915/123160 |
work_keys_str_mv |
AT hoyaarturo characteristicsofnaca2exchangeinfrogskeletalmuscle AT venosaroquealberto characteristicsofnaca2exchangeinfrogskeletalmuscle |
bdutipo_str |
Repositorios |
_version_ |
1764820449871527936 |