Dissociation between calcium influx blockage and smooth muscle relaxation by nifedipine in spontaneously hypertensive rats

Aortic smooth muscle isolated from spontaneously hypertensive rats (SHR) and normotensive, agematched Wistar Kyoto rats (WKY) was precontracted by potassium chloride. The relaxant effect of nifedipine (NIF) was much more pronounced in SHR than in WKY, while the relaxation produced by nitroglycerin (...

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Detalles Bibliográficos
Autores principales: Rinaldi, Gustavo, Cattaneo, Elizabeth Renée, Mattiazzi, Alicia Ramona, Cingolani, Horacio Eugenio
Formato: Articulo
Lenguaje:Inglés
Publicado: 1987
Materias:
Ciencias Médicas
Acceso en línea:http://sedici.unlp.edu.ar/handle/10915/138743
Aporte de:
SEDICI (UNLP) de Universidad Nacional de La Plata
id I19-R120-10915-138743
record_format dspace
institution Universidad Nacional de La Plata
institution_str I-19
repository_str R-120
collection SEDICI (UNLP)
language Inglés
topic Ciencias Médicas
spellingShingle Ciencias Médicas
Rinaldi, Gustavo
Cattaneo, Elizabeth Renée
Mattiazzi, Alicia Ramona
Cingolani, Horacio Eugenio
Dissociation between calcium influx blockage and smooth muscle relaxation by nifedipine in spontaneously hypertensive rats
topic_facet Ciencias Médicas
description Aortic smooth muscle isolated from spontaneously hypertensive rats (SHR) and normotensive, agematched Wistar Kyoto rats (WKY) was precontracted by potassium chloride. The relaxant effect of nifedipine (NIF) was much more pronounced in SHR than in WKY, while the relaxation produced by nitroglycerin (NTG) was similar in both tissues. EC50s were (in - log | M | ) NIF: SHR 13.1 ± 0.4 and WKY 9.4 ± 0.2 (p<0.05); NTG: SHR 7.35 ± 0.3 and WKY 7.26 ± 0.18 (NS). Aortas from SHR were less sensitive to the contractile effect of Ca2+ than their WKY controls (EC50 was 3.18 ± 0.03 in WKY and 2.76 ± 0.13 in SHR, p<0.05). The relaxant effect of NIF was dissociated from its effect on Ca2+ influx in SHR aortas. NIF 10"10 M relaxed the muscle by 100% without producing Ca2+ influx blockage, and NIF 10~9 and 10~8 M induced Ca2+ influx blockage while the muscle continued in the relaxed state. Chemically skinned aortic fibers from SHR were less sensitive to the contractile effect of Ca2+ than their normotensive (NR) controls (pCa for EC50 was 5.91 ± 0.05 in SHR and 6.20 ± 0.03 in NR, p<0.05). NIF 10-1 ° M depressed the contractile response to Ca2+ significantly more in SHR than in NR skinned fibers (pCa for EC50 for 5.62 ± 0.09 in SHR and 6.07 ± 0.07 in NR, p<0.05). These data suggest that 1) the more pronounced relaxant action of NIF on SHR aortas cannot be explained by its effect on Ca2+ influx, since both effects were dissociated in these vessels; and 2) the mechanism for NIF-dependent relaxation in SHR appears to be located not at the sarcolemmal but at some intracellular level. In this respect, a reduced calmodulin content in SHR arteries, along with an anticalmodulin action of NIF, could explain both the lesser sensitivity to Ca2+ and the greater sensitivity to NIF that was found in SHR aortas.
format Articulo
Articulo
author Rinaldi, Gustavo
Cattaneo, Elizabeth Renée
Mattiazzi, Alicia Ramona
Cingolani, Horacio Eugenio
author_facet Rinaldi, Gustavo
Cattaneo, Elizabeth Renée
Mattiazzi, Alicia Ramona
Cingolani, Horacio Eugenio
author_sort Rinaldi, Gustavo
title Dissociation between calcium influx blockage and smooth muscle relaxation by nifedipine in spontaneously hypertensive rats
title_short Dissociation between calcium influx blockage and smooth muscle relaxation by nifedipine in spontaneously hypertensive rats
title_full Dissociation between calcium influx blockage and smooth muscle relaxation by nifedipine in spontaneously hypertensive rats
title_fullStr Dissociation between calcium influx blockage and smooth muscle relaxation by nifedipine in spontaneously hypertensive rats
title_full_unstemmed Dissociation between calcium influx blockage and smooth muscle relaxation by nifedipine in spontaneously hypertensive rats
title_sort dissociation between calcium influx blockage and smooth muscle relaxation by nifedipine in spontaneously hypertensive rats
publishDate 1987
url http://sedici.unlp.edu.ar/handle/10915/138743
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