HIGH-PROTEIN DIET OR UNILATERAL NEPHRECTOMY INDUCES A HUMORAL FACTOR(S) THAT ENHANCES MESANGIAL CELL-PROLIFERATION IN CULTURE

Background: A high-protein diet is one of the maneuvers which produce hypertrophy of kidney mass. The underlying mechanism(s) has not been e lucidated. In the present study, we investigated the possibility that a humoral factor may be involved. Methods: Twenty-eight 3-week-old Cha rles River rats were studied. Fourteen underwent right nephrectomy and 14 sham operation. Each of these groups was divided into two equal su bgroups (n = 7 in each): one maintained on a regular diet (20% protein ) and the other on a high-protein diet (60% protein) for 7 days. Follo wing this period the animals were sacrificed. Sera from the animals we re added to mesangial cell cultures from kidneys of intact 3-week-old rats, and the thymidine incorporation was assessed. Results: The param eters of kidney mass indicated that the high-protein diet indeed produ ced kidney hypertrophy. Sera from the sham-nephrectomized animals fed a high-protein diet produced a significantly greater proliferative eff ect on mesangial cells in culture than sera from the respective animal s on a normal-protein diet. Sera from either nephrectomized group or f rom the high-protein sham-operated group all had similar magnitudes of enhancement of mesangial cell proliferation. Conclusion: We conclude that the renal hypertrophy produced by a high-protein diet is mediated , at least in part, by a humoral factor(s).