Effect of furosemide or mannitol before injection of a non-ionic contrast medium on intrarenal oxygen tension.

Oxygen tension (pO2) in rat renal cortex and outer medulla was studied after an intravenous injection of mannitol or furosemide, followed 10 minutes later by an intravenous injection of the non-ionic X-ray contrast medium (CM) iopromide (370 mg iodine/ml). Ten minutes after mannitol injection, before injection of CM, pO2 in the medulla had decreased from a control level of 32 +/- 3 to 28 +/- 4 mm Hg. The addition of CM caused a further decrease, to 24 +/- 5 mm Hg, which was a significant reduction. Ten minutes after furosemide injection the pO2 in the medulla had increased significantly, from a control value of 32 +/- 2 to 44 +/- 4 mm Hg. Injection of CM caused a significant decrease in pO2 to 37 +/- 3 mm. Ringer's solution (n = 6) caused no changes. We conclude that pretreatment with mannitol or furosemide does not prevent the CM-induced decrease in pO2 in the outer medulla.