Effect of increased oxygen on kidney function in the rat during and after 21 ATA He-O2 exposure

Two groups of four adult male rats each were exposed continuously for 12 d to 1.2 or 21 ATA He-O2 at 400 mm Hg 02. A third group was maintained under room-air conditions. Urine samples were collected every 12 h for the first 60 h of exposure and for the first 48 h post-decompression. Parameters measured included urine volume, urea, creatinine, calcium, and phosphate. In the 21-ATA group at pressure, urine volume and urea/creatinine increased, and total creatinine decreased; during recovery, total calcium, calcium/creatinine, and urea/creatinine increased and total phosphate decreased. In the 1.2-ATA group, during exposure, urea/creatinine and phosphate/creatinine increased. Diuresis in the 21-ATA group required 48 h to fully develop; however, recovery to normal occurred within 12 h post-decompression. The results reveal a moderate water diuresis and no serious alterations in kidney function during or after 21-ATA exposure at 400 mm Hg O2. There was a mild stress response at pressure and an undefined effect on calcium homeostasis post-decompression.