RELATIONSHIP BETWEEN THE DIURETIC EFFECT OF RADIOCONTRAST MEDIA AND THEIR ABILITY TO INCREASE RENAL VASCULAR-RESISTANCE

The relationship between diuresis and natriuresis induced by radiocont rast media (RCM) and their renal haemodynamic effects were investigate d. The effects of the iso-osmolar iotrolan and the hyperosmolar diatri zoate on the renal vascular resistance (RVR) were studied in the filte ring and non-filtering variants of the isolated perfused rat kidney (I PRK) preparation. In the non-filtering model, no tubular regulatory pr ocess can be activated. The effect of diatrizoate on the RVR of the fi ltering IPRK in the presence of frusemide (0.3 mmol 1(-1)) an inhibito r of the tubuloglomerular feedback (TGF) was also investigated. There was no significant difference (p > 0.05) in the response of the filter ing (n = 6) and non-filtering (n = 6) IPRK to iotrolan. The induced re duction in the renal perfusate flow (RPF) by iotrolan was 20.5 +/- 3.0 5% and 22.9 +/- 3.03%, respectively. The reduction in the RPF which wa s observed with diatrizoate in the non-filtering IPRR (n = 5, 17.5 +/- 3.04%) was significantly less (p < 0.05) in comparison to that of the filtering IPRK (n = 6, 26.9 +/- 4.28%). In the frusemide experiments, a reduction in the RPF comparable to that of the non-filtering kidney was observed (n = 5, 13.7 +/- 4.34%). This study demonstrates that th e renal vascular effect of diatrizoate is partially dependent on the T GF response. No tubular regulatory mechanism was accountable for the h aemodynamic effect of iotrolan. The activation of the tubular response is osmolarity dependent.