Passage of microspheres through vessels of normal and split hydronephrotic rat kidneys

Microspheres (15 micron) were injected intracardially in rats. By means of in vivo microscopy of the split hydronephrotic kidney microcirculation, the passage of microspheres through renal blood vessels was analyzed. Additionally, three sets of experiments were conducted, one consisting of rats with normal kidneys, one of rats with hydronephrotic kidneys, and one of rats with hydronephrotic kidneys under vasodilation. In vivo microscopic as well as histological studies show that the passage of 15-micron microspheres is dependent on the postinjection interval. Microspheres are capable of locally dilating preglomerular vessels and moving towards the glomeruli. Therefore, estimates of preglomerular vessel diameters with microsphere experiments ought to be controlled by intravital microscopy.