Characteristics of Na⁺‐Ca²⁺ exchange in frog skeletal muscle
- Autores
- Hoya, Arturo; Venosa, Roque Alberto
- Año de publicación
- 1995
- Idioma
- inglés
- Tipo de recurso
- artículo
- Estado
- versión publicada
- Descripción
- 1. Fluxes studies were carried out to investigate the Na⁺-dependent outward movement of Ca²⁺ in intact frog sartorius muscle from Leptodactylus ocellatus, 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⁺ (kCa,o) 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 kCa,o promoted by caffeine was decreased by: (a) 72% in the absence of external Na⁺ (Na⁺o); (b) 73% in Na⁺-loaded muscles ([Na⁺]i = 98 mM); (c) 70% when fibres were depolarized to -27 mV ([K⁺]o = 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 kCa,o. This effect of Ni²⁺ was associated with a concomitant caffeine-stimulated Ni²⁺ influx. In the absence of caffeine Ni²⁺ did not affect kCa,o. 6. It was concluded that: (a) under resting conditions the sarcolemmal Ca²⁺ pump suffices to handle the cytosolic calcium concentration ([Ca²⁺]i); (b) Na⁺-Ca²⁺ activity becomes apparent when [Ca²⁺]i 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.
Facultad de Ciencias Médicas - Materia
-
Medicina
Frog skeletal muscle
Caffeine
Medicinal chemistry
Na+-Ca2+ exchange - Nivel de accesibilidad
- acceso abierto
- Condiciones de uso
- http://creativecommons.org/licenses/by-nc-sa/4.0/
- Repositorio
- Institución
- Universidad Nacional de La Plata
- OAI Identificador
- oai:sedici.unlp.edu.ar:10915/123160
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Characteristics of Na⁺‐Ca²⁺ exchange in frog skeletal muscleHoya, ArturoVenosa, Roque AlbertoMedicinaFrog skeletal muscleCaffeineMedicinal chemistryNa+-Ca2+ exchange1. 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.Facultad de Ciencias Médicas1995-08-01info:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionArticulohttp://purl.org/coar/resource_type/c_6501info:ar-repo/semantics/articuloapplication/pdf615-627http://sedici.unlp.edu.ar/handle/10915/123160enginfo:eu-repo/semantics/altIdentifier/issn/0022-3751info:eu-repo/semantics/altIdentifier/doi/10.1113/jphysiol.1995.sp020839info:eu-repo/semantics/openAccesshttp://creativecommons.org/licenses/by-nc-sa/4.0/Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International (CC BY-NC-SA 4.0)reponame:SEDICI (UNLP)instname:Universidad Nacional de La Platainstacron:UNLP2025-09-29T11:29:18Zoai:sedici.unlp.edu.ar:10915/123160Institucionalhttp://sedici.unlp.edu.ar/Universidad públicaNo correspondehttp://sedici.unlp.edu.ar/oai/snrdalira@sedici.unlp.edu.arArgentinaNo correspondeNo correspondeNo correspondeopendoar:13292025-09-29 11:29:18.968SEDICI (UNLP) - Universidad Nacional de La Platafalse |
dc.title.none.fl_str_mv |
Characteristics of Na⁺‐Ca²⁺ exchange in frog skeletal muscle |
title |
Characteristics of Na⁺‐Ca²⁺ exchange in frog skeletal muscle |
spellingShingle |
Characteristics of Na⁺‐Ca²⁺ exchange in frog skeletal muscle Hoya, Arturo Medicina Frog skeletal muscle Caffeine Medicinal chemistry Na+-Ca2+ exchange |
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 |
dc.creator.none.fl_str_mv |
Hoya, Arturo Venosa, Roque Alberto |
author |
Hoya, Arturo |
author_facet |
Hoya, Arturo Venosa, Roque Alberto |
author_role |
author |
author2 |
Venosa, Roque Alberto |
author2_role |
author |
dc.subject.none.fl_str_mv |
Medicina Frog skeletal muscle Caffeine Medicinal chemistry Na+-Ca2+ exchange |
topic |
Medicina Frog skeletal muscle Caffeine Medicinal chemistry Na+-Ca2+ exchange |
dc.description.none.fl_txt_mv |
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. Facultad de Ciencias Médicas |
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. |
publishDate |
1995 |
dc.date.none.fl_str_mv |
1995-08-01 |
dc.type.none.fl_str_mv |
info:eu-repo/semantics/article info:eu-repo/semantics/publishedVersion Articulo http://purl.org/coar/resource_type/c_6501 info:ar-repo/semantics/articulo |
format |
article |
status_str |
publishedVersion |
dc.identifier.none.fl_str_mv |
http://sedici.unlp.edu.ar/handle/10915/123160 |
url |
http://sedici.unlp.edu.ar/handle/10915/123160 |
dc.language.none.fl_str_mv |
eng |
language |
eng |
dc.relation.none.fl_str_mv |
info:eu-repo/semantics/altIdentifier/issn/0022-3751 info:eu-repo/semantics/altIdentifier/doi/10.1113/jphysiol.1995.sp020839 |
dc.rights.none.fl_str_mv |
info:eu-repo/semantics/openAccess http://creativecommons.org/licenses/by-nc-sa/4.0/ Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International (CC BY-NC-SA 4.0) |
eu_rights_str_mv |
openAccess |
rights_invalid_str_mv |
http://creativecommons.org/licenses/by-nc-sa/4.0/ Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International (CC BY-NC-SA 4.0) |
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application/pdf 615-627 |
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