Influence of Renal Function on the Urinary Excretion of Amylase

Abstract

Urinary excretion of endogenous amylase was studied during osmotic diuresis in normal rats and in rats with different kinds of induced kidney damage. In normal rats the amylase excretion varied almost proportionally with respect to plasma concentration of amylase and to glomerular filtration rate (GFR), estimated as clearance for polyethylene glycol 1000 (PEG 1000). The ratio between amylase clearance and GFR varied only slightly with body weight and was independent of urine flow in normal rats. Both increased glomerular permeability to proteins in aminonucleoside-nephrosis and tubular dysfunction after sodium maleate treatment augmented the ratio of amylase clearance to GFR. A considerable tubular reabsorption of amylase in normal rats is concluded. In unilateral pyelonephritis or unilateral ischemic kidney damage this ratio remained constant, but when the functional kidney mass was reduced by removal of the intact kidney, it increased considerably, possibly owing to decreased fractional reabsorption of fluid in the proximal tubules and increased glomerular filtration of proteins per nephron.

Key Words:

• Amylase
• glomerular filtration rate
• proteinuria
• renal tubular function