Differences in cortical microcirculation in the kidneys of unilaterally congenital hydronephrotic rats

The surgically induced split hydronephrotic kidney has been generally accep ted as a valid model for the assessment of renal microcirculation by means of intravital microscopy. Whereas nearly all previous work on this issue ha s been done with a transillumination technique, we used an epiillumination model that is suitable for investigation of microvascular perfusion in both normal and hydronephrotic kidneys without surgical manipulation of the ure ter. By means of the congenital unilaterally hydronephrotic Tauchi rat, mic rocirculation of the hydronephrotic and that of the nonhydronephrotic kidne y were compared. For that purpose both the hydronephrotic and the nonhydron ephrotic kidneys of Tauchi rats were exteriorized on a specially designed m icroscopy stage. After injection of FITC-dextran and rhodamine 6G, microvas cular perfusion was assessed in both kidneys. The new model allowed visuali zation of arterioles, capillaries, and postcapillary venules in both the hy dronephrotic and the nonhydronephrotic kidneys. Glomeruli could only be reg ularly seen in the hydronephrotic kidney, but also in some normal kidneys. Capillary blood cell velocity was significantly higher in the hydronephroti c kidneys (0.67 +/-0.03 mm/s) compared to the normal kidney (0.32 +/-0.05 m m/s; P<0.05), whereas capillary diameters were smaller (4.2<plus/minus>0.02 mum vs. 5.7 +/-0.2 mum; P<0.05). In addition, the hydronephrotic kidney sh owed a significantly lower density of perfused microvessels compared to the normal controls. Epiillumination intravital microscopy allows assessment o f the cortical microcirculation in both the hydronephrotic and the nonhydro nephrotic kidneys without surgical inductin of hydronephrosis. The hydronep hrotic kidney shows significant microcirculatory differences compared to no rmal kidneys that should be taken into account when using a hydronephrotic model for pharmacological testing. (C) 2001 Academic Press.