Temporal alterations in regional gene expression after nephrotoxic renal injury

To examine at a molecular level the repair process during recovery from acute renal failure, we determined, after nephrotoxic acute renal injury, levels for several RNAs associated with differentiated functions in the kidney. To delineate changes in different regions, we determined RNA levels separately in cortex, outer medulla, and inner medulla of adult rat kidney. Several RNAs were regionally distributed in control kidneys, including epidermal growth factor (EGF, highest in cortex and outer medulla), aldose reductase (highest in inner medulla), and prostaglandin synthase (highest in inner medulla). Futhermore, RNA for the heat shock protein Hsp70 was present at high levels in the inner medulla of controls. A single intraperitoneal dose of folic acid caused reversible, nonoliguric acute renal failure with impairment of glomerular filtration, tubular sodium reabsorption, and urinary concentration. Fractional excretion of sodium returned to normal by day 3, while serum creatinine, serum urea nitrogen, and urinary osmolality remained abnormal until day 7. During acute renal failure there was a marked, reversible decrease in the regional mRNA levels for EGF, aldose reductase, prostaglandin synthase, and Hsp70. Aldose reductase, prostaglandin synthase, and Hsp70 RNA levels returned to control levels by 7 to 10 days, while EGF remained depressed for a more prolonged period. High levels of aldose reductase, prostaglandin synthase, and Hsp70 RNAs in the inner medulla and their loss/recovery during acute renal failure with a time course similar to alterations in urinary osmolality were consistent with regulation in response to changes in inner medullary osmolality, as has been demonstrated for aldose reductase in normal animals. (ABSTRACT TRUNCATED AT 250 WORDS)