Tamm-Horsfall protein (THP) and epidermal growth factor (EGF) are both
synthesized by tubular cells in the distal part of the nephron and ex
creted with the urine. The present study examines the urinary excretio
n rates of the two peptides in relation to functional tubular markers
in patients with chronic nephropathy. Four groups of patients with mod
erate to severely reduced renal function were studied: glomerulonephri
tis (n = 10), diabetic nephropathy (n = 11), tubulointerstitial nephro
pathy (n = 13), and polycystic kidney disease (n = 8). The renal funct
ion was evaluated by glomerular filtration rate (GFR) as an indicator
for the general renal function, lithium clearance (C-Li) as an indicat
or for proximal tubular function, and absolute distal reabsorption of
sodium (ADR(NA)) as an indicator for distal tubular function. The excr
etion rate of EGF was rather closely correlated with GFR, C-Li and ADR
(NA) (Spearman coefficients of variation 0.88, 0.69, and 0.74, respect
ively). The correlations between the excretion rate of THP and GFR, C-
Li and ADR(NA) were weaker (Spearman coefficients of variation 0.68, 0
.42, and 0.44). When the effect of GFR had been accounted for by multi
ple variance analyses, the excretion rates of the two peptides were st
ill associated with ADR(NA) but not with C-Li In conclusion, the urina
ry excretion rates of especially EGF but also those of THP were correl
ated with renal function and distal tubular reabsorption of sodium in
patients with chronic nephropathy.