Beneficial effect of fibronectin administration on chronic nephritis in rats

We studied the effect of fibronectin (FN) on the course of chronic nephritis (induced by daily injections of ovalbumin) and on the clearance and catabolism of immune complexes in Wistar rats. Rats with chronic nephritis were treated with FN (2.5 mg/kg/48 hours) for 15 days after proteinuria was first detected. In rats with untreated nephritis, urinary protein levels increased from 40 +/- 22 mg/day (mean +/- SD) to 339 +/- 68 mg/day during the 15 days of the study (P less than 0.0005). This statistically significant increase was not observed in rats treated with FN (mean +/- SD 58 +/- 46 mg/day to 124 +/- 112 mg/day). Rats treated with FN showed a higher total serum protein level than did the untreated animals (mean +/- SD 6.4 +/- 0.3 gm/dl versus 5.1 +/- 0.5 gm/dl; P less than 0.0125), as well as a significant reduction in mesangial and glomerular basement membrane deposits. Untreated nephritic rats demonstrated delayed plasma clearance of 125I-labeled aggregated IgG (plasma half-life T1/2] 3.03 +/- 0.6 minutes) and less catabolism of these aggregates at 30 minutes (mean +/- SD 15 +/- 1.7%) than did the normal rats (T1/2 1.5 +/- 0.2 minutes, 22 +/- 2.8%, respectively; P less than 0.0005). Both parameters were within normal limits in the FN-treated rats (T1/2 1.6 +/- 0.4 minutes, 22 +/- 6%, respectively). In vitro, FN induced a significant increase in aggregated IgG catabolism by Kupffer cells and peritoneal macrophages from normal rats. These results show that FN reduces the proteinuria and histologic lesions of chronic nephritis in rats.(ABSTRACT TRUNCATED AT 250 WORDS)