Renal Disposition of Amylase, Lipase, and Lysozyme in the Dog

Abstract

Abstract. Normal adult dogs were given intravenously lysine hydrochloride to abolish renal tubular reabsorption. The treatment caused tubular proteinuria. Once forced diuresis was established, fractional clearances for amylase, lipase, and lysozyme increased five-, 18-, and 857-fold over the baseline values, respectively. There was relatively little tubular reabsorption of amylase, and urinary amylase activity remained low. A renal arteriovenous difference in amylase activity was not present. Urinary amylase activity could not be reactivated by the addition of serum or treatment with dithiothreitol. Urinary inhibitors of amylase activity were not detected. Immunoreactive urinary amylase did not exceed kinetically measured urinary amylase. Therefore, the presence of irreversibly inactivated amylase did not explain the low fractional clearance of amylase. A small amount of serum macroamylase was present, but macroamylasemia did not account for canine amylase failing to pass the glomerular filter. It appears that the renal loss of amylase in the dog is not an important excretory route.Canine a-amylase has a molecular weight of 54 kilod a l t o n~,~ which is similar to human a-amylase.8 In both species, the kidney is believed to be an important excretory route for amylase.11,28 In man, the measurement of urinary amylase activity and amylase clearance in relation to creatinine can have diagnostic importance.I5 The renal clearance rate of amylase in the dog is reported to be similar to the rate in man." Dogs have greater than twice the serum amylase activity compared with man, yet they have normally little or undetectable urinary amylase activity. Even with greatly increased serum amylase activity resulting from experimentally induced pancreatitis or infusion of supernates of pancreatic homogenates, the urinary loss of amylase appears minimal in d o g~.~,~,~J~,~~ It has been hypothesized that canine amylase is inactivated in the glomerular filtrate by unknown mechanisms or is reabsorbed by tubular epithelial cells.L1 Metabolic inhibitors of canine renal tubular epithelial cells increased the amylase to creatinine clearance ratio, suggesting that tubular cells normally reabsorbed amylase activity; however, the influence on the ratio of decreased creatinine secretion by the metabolically inhibited tubular epithelial cells was not ~0nsidered.I~ The low concentrations of urinary calcium and protein may cause urinary amylase activity to be lower than anticipated, since both are needed for optimal activity,12,23 although urinary amylase activity does not appear to be inhibited in man in such a manner. Changes to essential sulfhydryl groups in the amylase molecule also may result in enzyme inactivation, as reported for human amy1a~e.I~ It is possible that canine urine may contain inhibitors of amylase activity, but early data based on a saccharogenic technique for measuring amylase activity do not support this hypothesis.15 In man, approximately 45% of filtered amylaseZ8 and almost all lipase19 are reabsorbed by renal tubula...

Hyperlipasemia in 6 Dogs with Pancreatic or Hepatic Neoplasia: Evidence for Tumor Lipase Production

“…Results of studies regarding the elimination of canine serum α‐amylase are less definitive. At least a portion of total serum α‐amylase is filtered by glomeruli and metabolized or secreted in the urine 17 . Extrarenal mechanisms for elimination of the remaining serum α‐amylase have not been elucidated 17 , 18 .…”

“…At least a portion of total serum α‐amylase is filtered by glomeruli and metabolized or secreted in the urine 17 . Extrarenal mechanisms for elimination of the remaining serum α‐amylase have not been elucidated 17 , 18 . In human beings, hepatic clearance of α‐amylase is suspected 19 .…”

“…17 Extrarenal mechanisms for elimination of the remaining serum ␣amylase have not been elucidated. 17,18 In human beings, hepatic clearance of ␣-amylase is suspected. 19 Because serum PL and ␣-amylase are eliminated, at least in part, by the kidneys, increases in the activities of both enzymes can occur with decreased glomerular filtration.…”

Glomerular Filtration Rate and Renal Volume in Dogs with Congenital Portosystemic Vascular Anomalies before and after Surgical Ligation

“…26,27 Other studies have yielded conflicting results about the renal elimination of amylase. 28,29 The magnitude of change in GFR in individual dogs was not consistently associated with the magnitude or direction of change in serum amylase activity. Similarly, changes in BUN and creatinine concentrations in individual dogs showed no consistent association with changes in amylase activity.…”

“…The presence of macroamylasemia has been reported in the dog. 29 Large protein-amylase complexes are not freely filtered by the glomerulus and might account, in part, for the increased enzyme activity reported in animals with renal failure. 30 Alterations in plasma proteins in dogs with PSVA could be involved in changes in macroamylase activity.…”