Distribution, turnover, and mechanism of renal excretion of amylase in the baboon

Abstract

A B S T R A C T Pure amylase was isolated from pancreata and parotid glands of the baboon, an animal which has a serum amylase level and renal clearance of amylase (CAm) similar to man. After bolus injection, both pancreatic and salivary amylase rapidly disappeared from the serum in a monoexponential fashion with a mean serum half-time of approximately 83 min. Only about 24% of the amylase cleared from the serum appeared in the urine indicating that the majority of amylase was removed from the serum by an extraurinary mechanism. The CA. by the kidney was constant over a wide range of serum amylase levels and the ratio of CAm/CI, which averaged 3.0%, was not influenced by mannitol diuresis. This suggests that the renal excretion of amylase results from glomerular filtration without appreciable tubular reabsorption. Pancreatic amylase was consistently cleared more rapidly by the kidney than was the baboon's endogenous amylase while salivary amylase was consistently cleared less rapidly than endogenous amylase.The findings in this study provide insight into several of the following clinically observed phenomena: (a) the short serum half-time of atpylase accounts for the transient nature of serum amylase elevations in pancreatitis; (b) the extra-urinary removal of amylase accounts for the maintenance of relatively normal amylase levels in uremia; and (c) the more rapid renal clearance of pancreatic amylase compared to salivary amylase may explain the disproportionate elevation of the urinary amylase excretion rate relative to the serum amylase level in acute pancreatitis.

Simultaneous study of the metabolic turnover and renal excretion of salivary amylase-125I and pancreatic amylase-131I in the baboon

“…Interpretation of previous studies of the turnover of serum amylase are limited by the use of laboratory animals not comparable to man in regard to serum amylase levels and renal amylase clearance (1,2), by the use of amylase heterologous to the animals studied (2,3), and lastly, by the need to markedly elevate serum amylase levels in order to measure the removal rate of the unlabeled enzyme from the serum (1)(2)(3)(4).…”

“…The glycogen precipitation technique of Loyter and Schramm (8) was used to isolate amylase from baboon parotid gland and pancreas as previously described (4). The purity of amylase was assessed by gel filtration and electrophoresis as described in a previous paper (4).…”

Heritability of urine and plasma amylase activity

“…As to the rates of Amy 1 or Amy 2 in plasma and urine it is well known that pancreatic isozyme is considerably more rapidly cleared by the kidney (Levitt et al, 1969;Duane et al, 1971Duane et al, , 1972. In serum, activity of pancreatic isozyme comprised less than half the total activity, 26.7 to 49.1~, according to the Fridhandler et al (1972).…”

Tests of Exocrine Pancreatic Function

“…Only 24% of amylase cleared from the blood after infusion is excreted by the kidney (Duane et al, 1971). The rate of urinary excretion can be satisfactorily determined on a timed random specimen and 24 hour collections are unnecessary (Klein and Foreman, 1973;Waller and Ralston, 1971).…”

“…A relative increase in amylase clearance is also recorded in acute pancreatitis, (Blainey and Northam, 1967;Levitt et af., 1969;Waller and Ralston, 1971). This arises from the fact that pancreatic isoamylase has a higher clearance than salivary isoamylase (Duane et al, 1971;Fridhandler et al, 1972).…”