Spectrum of diurnal rhythms in glomerular permeability in patients with membranous nephropathy

Diurnal rhythms in proteinuria and selectivity index (SI) of proteinuria can vary from patient to patient with respect to phase and amplitude (A/M) and in some cases rhythms are absent. The aim of the present study was to relate this variability to a different pattern of diurnal rhythms in permselectivity of the glomerular capillary wall (GCW).

Ten patients with nephrotic syndrome due to membranous nephropathy were studied. Diurnal rhythmicity in size-dependent permselectivity of the GCW was determined by measuring 3-h fractional clearances of dextrans (30-90 A) over a period of 1 day.

Four types of rhythmicity could be recognized. Type I and II only differed in the magnitude of the diurnal variability in glomerular transport through large pores (r2) and shunt pathway (omega). Both had normal rhythms in clearance of proteins and SI, but all rhythms were more pronounced in the patients with normal renal function and mild histological abnormalities (type II). Although type III also had a normal GFR and minor histological lesions, only transport through omega (and not through r2) showed a significant diurnal rhythm, which implied that this type did not have a normal rhythm in SI. The patients with advanced renal failure and extensive interstitial lesions neither had a rhythm in permselectivity nor had normal rhythms for proteinuria and SI (type IV).

The type of rhythmicity in glomerular permeability corresponds well with the presence and phase of rhythms in clearance of proteins and in SI of the proteinuria.