The effect of chronic nitric oxide inhibition on vascular reactivity and blood pressure in pregnant rats
Palavras-chave:
Vascular reactivity, Pregnancy, Rats; L-NAME, Nitric oxideResumo
CONTEXTO: Os mecanismos envolvidos na diminuição da pressão arterial e da resistência vascular periférica da gravidez não são totalmente esclarecidos, assim como a real importância do fator relaxante derivado do endotélio (Endothelium-derivated relaxing factors - EDRF), um importante modulator do tônus vascular. OBJETIVO: O trabalho avaliou a importância do EDRF e seu principal componente, óxido nitrico, na prenhez das ratas. TIPO DE ESTUDO: Experimentação clínica em animal. LOCAL: Laboratório Universitário de Farmacologia. VARIÁVEIS ESTUDADAS: Foram avaliados, em ratas Wistar normotensas, virgens ou prenhes, a influência da inibição crônica da síntese de óxido nítrico, utilizando o Nw-nitro-L-arginina (L-NAME) diluído na água ingerida pelos animais durante 10 dias e comparadas com os respectivos grupos controles. Foram analisados as repercussões da prenhez e do L-NAME sobre a pressão arterial, reatividade vascular da aorta a acetilcolina in vitro e resultados perinatais. RESULTADOS: A pressão arterial caudal diminui no final da prenhez. A sensibilidade da aorta das ratas prenhes à acetilcolina foi maior que nas virgens. O tratamento com L-NAME determinou aumento da pressão arterial caudal em ambos os grupos de animais e determinou bloqueio no relaxamento induzido pela acetilcolina, de modo semelhante a retirada mecânica do endotélio da aorta. O grupo de ratas prenhes que ingeriram L-NAME apresentou peso da ninhada e do peso de cada feto menor que o grupo controle. CONCLUSÕES: Demonstramos maior sensibilidade para acetilcolina na gestação, contribuindo com a diminuição da pressão arterial e um bloqueio no relaxamento induzido pela acetilcolina após administração de L-NAME.
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