Acute haemodynamic and proteinuric effects of prednisolone in patients with a nephrotic syndrome

Administration of prednisolone causes an abrupt rise in proteinuria in patients with a nephrotic syndrome.

To clarify the mechanisms responsible for this increase in proteinuria we have performed a placebo controlled study in 26 patients with a nephrotic syndrome. Systemic and renal haemodynamics and urinary protein excretion were measured after prednisolone and after placebo.

After i.v. administration of 125-150 mg prednisolone total proteinuria increased from 6.66+/-4.42 to 9.37+/-6.07 mg/min (P<0.001). By analysing the excretion of proteins with different charge and weight (albumin, transferrin, IgG, IgG4 and beta2-microglobulin) it became apparent that the increase of proteinuria was the result of a change in size selectivity rather than a change in glomerular charge selectivity or tubular protein reabsorption. Glomerular filtration rate rose from 83+/-34 ml to 95+/-43 ml/min (P<0.001) after 5 h, whereas effective renal plasma flow and endogenous creatinine clearance remained unchanged. As a result filtration fraction was increased, compatible with an increased glomerular pressure, which probably contributes to the size selectivity changes. Since corticosteroids affect both the renin-angiotensin system and renal prostaglandins, we have evaluated the effects of prednisolone on proteinuria after pretreatment with 3 months of the angiotensin-converting enzyme inhibitor lisinopril or after 2 weeks of the prostaglandin synthesis inhibitor indomethacin. Neither drug had any effect on prednisolone-induced increases of proteinuria.

Prednisolone increases proteinuria by changing the size selective barrier of the glomerular capillary. Neither the renin-angiotensin axis nor prostaglandins seem to be involved in these effects of prednisolone on proteinuria.