The ability of atrial natriuretic peptide (ANP) to prevent cisplatin-induced nephrotoxicity was compared to the protective effect of 3% NaCl. ANP (1 microgram/kg/min), 3% NaCl or peptide buffer vehicle (50 microliters/min) were infused for 45 min to conscious unrestrained rats immediately after cisplatin administration (5 mg/kg i.v.). Measurements taken 72 h after drug treatment indicated that compared to animals receiving cisplatin only, ANP co-treated rats had lower post-treatment plasma creatinine concentrations (0.70 +/- 0.07 vs 1.3 +/- 0.17 mg/dl; P < 0.05), blood urea nitrogen (BUN) concentrations (44.2 +/- 5.8 vs. 65.5 +/- 2.1 mg/dl; P < 0.05) and higher post-treatment glomerular filtration rates (GFR) (0.71 +/- 0.18 vs. 0.14 +/- 0.03 ml/min; P < 0.05). ANP was as effective as 3% NaCl in preventing cisplatin nephrotoxicity in this model. The effect of ANP co-treatment on the anti-tumor activity of cisplatin was also examined using the Walker 256 carcinosarcoma model. ANP treatment did not result in any observable loss in anti-tumor activity. When ANP was administered 72 h after cisplatin treatment, improvement in GFR was observed for the duration of the infusion, confirming the beneficial effect of ANP on cisplatin-damaged kidneys. ANP may have a role in the treatment and prevention of cisplatin nephrotoxicity especially in clinical situations where treatment with a large fluid volume is contraindicated.