Novel model for calcium paradox in sympathetic transmission of smooth muscles: Role of cyclic AMP pathway
Data
2013-09-01
Autores
Bergantin, Leandro Bueno 
Souza, Claudio Fontes
Ferreira, Regiane Miranda
Smaili, Soraya Soubhi
Jurkiewicz, Neide Hyppolito
Mostrar mais
Tipo
Artigo
Título da Revista
ISSN da Revista
Título de Volume
Resumo
It is well established that reduction of Ca2+ influx through L-type voltage-dependent Ca2+ channel (L-type VDCC), or increase of cytosolic cAMP concentration ([cAMP]c), inhibit contractile activity of smooth muscles in response to transmitters released from sympathetic nerves. Surprisingly, in this work we observed that simultaneous administration of L-type VDCC blocker (verapamil) and [cAMP]c enhancers (rolipram, IBMX and forskolin) potentiated purinergic contractions evoked by electrical field stimulation of rat vas deferens, instead of inhibiting them. These results, including its role in sympathetic transmission, can be considered as a calcium paradox. On the other hand, this potentiation was prevented by reduction of [cAMP]c by inhibition of adenylyl cyclase (SQ 22536) or depletion of Ca2+ storage of sarco-endoplasmic reticulum by blockade of Ca2+ reuptake (thapsigargin). in addition, cytosolic concentration ([Ca2+](c)) evaluated by fluorescence microscopy in rat adrenal medullary slices was significantly reduced by verapamil or rolipram. in contrast, simultaneous incubation of adrenal slices with these compounds significantly increased [Ca2+](c). This effect was prevented by thapsigargin. Thus, a reduction of [Ca2+](c) due to blockade of Ca2+ influx through L-type VDCC could stimulate adenylyl cyclase activity increasing [cAMP]c thereby stimulating Ca2+ release from endoplasmic reticulum, resulting in augmented transmitter release in sympathetic nerves and contraction. (C) 2013 Elsevier B.V. All rights reserved.
Descrição
Citação
Cell Calcium. Edinburgh: Churchill Livingstone, v. 54, n. 3, p. 202-212, 2013.