Effects of transient hypotension on the structure and function of rat kidney

The immediate effects on renal structure and function of 60 or 90 min of hypotension and the effects of one to four days of recovery were studied in the rat. An initial diuresis occurred during the first day after hypotension, followed by decreased urine volumes. Along with the diuresis, the animals secreted a hypo-osmolar urine for two days following hypotension, which returned to a normal concentration at three days. Twentyfour hour urine sodium excretion was depressed during the first and second days after hypotension while potassium excretion was no different from that of control animals. The morphologic alterations of tissue fixed immediately following 60 and 90 min of hypotension were greatest in the pars recta of the proximal tubule but were also seen focally in the pars convoluta. The cellular changes included dilated endoplasmic reticulum, clumped nuclear chromatin, swollen mitochondria with small flocculent densities, and the formation of multivesicular bodies. One day after the hypotension, cell death and necrosis were observed extensively in the pars recta. This study describes an experimental model for the study of the renal effects of hypovolemic shock in rats.