RESUMO
Aquaporin-1 (AQP1) is expressed in the heart and its relationship with NO system has not been fully explored. The aims of this work were to study the effects of NO system inhibition on AQP1 abundance and localization and evaluate AQP1 S-nitrosylation in a model of water restriction during postnatal growth. Rats aged 25 and 50days (n=15) were divided in: R: water restriction; C: water ad libitum; RL: L-NAME (4mg/kgday)+water restriction; CL: L-NAME+water ad libitum. AQP1 protein levels, immunohistochemistry and S-nitrosylation (colocalization of AQP1 and S-nitrosylated cysteines by confocal microscopy) were determined in cardiac tissue. We also evaluated the effects of NO donor sodium nitroprusside (SNP) on osmotic water permeability of cardiac membrane vesicles by stopped-flow spectrometry. AQP1 was present in cardiac vascular endothelium and endocardium in C and CL animals of both ages. Cardiac AQP1 levels were increased in R50 and RL50 and appeared in cardiomyocyte plasma membrane. No changes in AQP1 abundance or localization were observed in R25, but RL25 group showed AQP1 presence on cardiomyocyte sarcolemma. AQP1 S-nitrosylation was increased in R25 group, without changes in the 50-day-old group. Cardiac membrane vesicles expressing AQP1 presented a high water permeability coefficient and pretreatment with SNP decreased water transport. Age-related influence of NO system on AQP1 abundance and localization in the heart may affect cardiac water homeostasis during hypovolemic state. Increased AQP1 S-nitrosylation in the youngest group may decrease osmotic water permeability of cardiac membranes, having a negative impact on cardiac water balance.
Assuntos
Aquaporina 1/metabolismo , Miocárdio/metabolismo , Miocárdio/patologia , Óxido Nítrico/metabolismo , Pressão Osmótica , Animais , Animais Recém-Nascidos , Pressão Sanguínea/efeitos dos fármacos , Membrana Celular/efeitos dos fármacos , Membrana Celular/metabolismo , Permeabilidade da Membrana Celular/efeitos dos fármacos , Ventrículos do Coração/efeitos dos fármacos , Ventrículos do Coração/metabolismo , Imuno-Histoquímica , Masculino , Membranas/efeitos dos fármacos , Modelos Biológicos , NG-Nitroarginina Metil Éster/farmacologia , Doadores de Óxido Nítrico/farmacologia , Óxido Nítrico Sintase/metabolismo , Nitrosação , Pressão Osmótica/efeitos dos fármacos , Ratos Sprague-Dawley , Reprodutibilidade dos Testes , Espalhamento de Radiação , Sístole/efeitos dos fármacos , ÁguaRESUMO
PURPOSE: During the postnatal stage, cardiovascular nitric oxide (NO) system and caveolins (cav) may be regulated differentially in response to hypovolemic state induced by water restriction. Our aim was to examine the effects of water restriction on NO synthases (NOS) and cav in the atria, ventricle and aorta of growing rats. METHODS: Male Sprague-Dawley rats aged 25 and 50 days were divided into (n = 15): WR: water restriction 3 days; WAL: water ad libitum 3 days. Systolic blood pressure, NOS activity and NOS/cav protein levels were measured. RESULTS: Dehydration induced a larger increase in SBP in WR25 group. Ventricular NOS activity, endothelial NOS (eNOS) and neuronal isoform (nNOS) of WR25 pups were increased, and both cav were decreased. In the WR50 group, NOS activity remained unchanged. In the atria, NOS activity, eNOS and nNOS decreased in WR25 associated with increased cav-1; in the WR50 group, NOS activity was increased without changes in NOS isoforms. In the aorta of WR25, NOS activity and inducible NOS (iNOS) were decreased; NOS activity was unchanged in WR50, despite the decreased levels of eNOS and increased iNOS, cav-1 and cav-3. CONCLUSIONS: NO system adjustments in cardiovascular system under osmotic stress in vivo depend on postnatal age, being eNOS and nNOS, the isoforms that determine NOS activity in cardiac tissue in 25-day-old pups. Changes in cav abundance during hypovolemic state may contribute to age-related NO production.
