Heterogeneity of glomerular perfusion and filtration induced by epinephrine and norepinephrine

The role of catecholamines in the distribution of intrarenal blood flow and in single-nephron glomerular filtration rate (SNGFR) was evaluated in anesthetized Wistar rats by the Hanssen technique. Epinephrine (EPI) and norepinephrine (NOR) were infused to produce elevations of 20-30 mmHg in mean arterial pressure. Superficial and juxtamedullary nephron perfusion and filtration were determined by the presence of Prussian blue dye. In the control group, 100 per cent of the nephrons presented a homogeneous pattern of perfusion and filtration. In contrast, a heterogenous distribution of the dye was found even in the larger arteries (arciform and radial), indicating variable perfusion and filtration in both superficial and juxtamedullary nephrons. The effects of EPI and NOR were also evaluated in the superficial cortex by the micropuncture technique in two additional groups of Munich-Wistar rats. Mean SNGFR was 27 per cent and 54 per cent lower in the EPI-and NOR-treated groups, respectively. No change in mean intraglomerular hydraulic pressure was observed after EPI or NOR infusion in spite of a highly scattered pattern, indicating an important variability in perfusion along the superficial cortex, and/or different sensitivity of the pre-and post-glomerular arterioles. The present data suggest that EPI and NOR may affect intrarenal hemodynamics by modifying perfusion and filtration in both superficial and juxtamedullary glomeruli and not by shifting blood folow from superficial to juxtamedullary nephrons. The heterogenous pattern of perfusion was a consequence of differential vasoconstriction along the intrarenal arteries, probably due to different density and/or sensitivity of the adrenergic receptor subtypes present in the intrarenal vascular tree.

Estudio do efeito de Donnan em solucoes utilizadas para a microperfusao isolada do tubulo renal "in vitro". / Study of Donnan effect in solutions used for isolated microperfusion of the renal tubule \"in vitro\"

Neste trabalho foi estudada a importancia do efeito de Donnan durante a feitura de solucoes utilizadas na microperfusao isolada do tubulo contornado proximal in vitro. Nas nossas condicoes experimentais observamos a existencia do efeito de Donnan nesta preparacao, avaliada pelas medidas de sodio, calcio e consequentes alteracoes da osmolaridade. Assim, observamos nesta preparacao que a correcao do pH 7,4, para evitar precipitados e para manter a viabilidade celular, consiste num fator importante na deteccao de um fenomeno semelhante ao efeito de Donnan. Este achado se torna mais evidente durante a ultrafiltracao, o que nos levou a fazer uma correcao da osmolariadade do ultrafiltrado de 8mOsm/kg/H2O com relacao ao banho, para a obtencao de condicoes de isosmolaridade

Avaliação clinica do efeito do verapamil em pacientes hipertensos / Clinical evaluation of the effect of verapamil in hypertensive patients

Os autores estudaram 20 pacientes com hipertensão essencial e função renal normal. O efeito do verapamil, em diferentes associações por períodos de 14 dias, foi avaliado através da determinação da pressão arterial na posição deitada e em pe, da frequência cardíaca e do intervalo P-R. Os vários períodos foram comparados quanto as variáveis estudadas bem como quanto aos efeitos colaterais