Intravital microscopical studies of the tubular urine flow in the conscious rat.

A method was developed which allowed microscopical observation of the kidney in conscious and anesthetized rats. The left kidney was freed from surrounding tissue and placed in a plexiglas chamber with a protecting window which was sewed into the skin of left flank. During the experiments the covering glass was removed. Tubular transit time was measured in the conscious state and during inactin anesthesia in control rats as well as in unilaterally nephrectomized rats with compensatory hypertrophy. Transit time of lissamine green within proximal convolutions and Henle's loop increased significantly in both series during anesthesia. Luminal and outer diameters of proximal tubules in control rats were evaluated from microphotogramms of the kidney surface, they did not change due to anesthesia. The results could be mainly explained by a decrease in glomerular filtration rate due to anesthesia. Possible mechanisms are discussed which could explain the observed transit time in Henle's loops and distal convolutions in control and uninephrectomized rats.