AJP - Gastrointestinal and Liver Physiology, Vol 247, Issue 3 273-G278, Copyright © 1984 by American Physiological Society
Metabolism of human isoamylases in the rabbit
J. L. Rosenblum, T. E. Niesen and D. H. Alpers
Human isoamylases were purified from pancreas and saliva with separation of
salivary isoenzymes into glycosylated and nonglycosylated forms. After
iodination, bolus injection of each purified isoamylase into conscious
rabbits revealed biexponential disappearance from plasma. Glycosylated
salivary amylase had a metabolic clearance (t 1/2 = 35 min) that was three
to four times faster than nonglycosylated salivary (t 1/2 = 139 min) or
pancreatic (t 1/2 = 111 min) amylase. In contrast to our previous studies
on homologous (rabbit) isoamylases, human pancreatic isoamylase was
excreted into urine as protein-bound radioactivity more readily than
salivary isoamylase. No organ contained more than 18% of the injected dose
of radioactivity except for a striking accumulation of radioactivity in the
liver after injection of 125I-labeled glycosylated salivary amylase. We
concluded that 1) human nonglycosylated salivary amylase and pancreatic
amylase are cleared from the rabbit circulation at rates comparable with
those reported for homologous isoamylases in the rabbit and baboon, 2) the
rabbit kidney excretes human pancreatic amylase into urine more readily
than human salivary isoamylases, and 3) with the notable exception of
glycosylated salivary isoamylase, human isoamylases do not appear to be
metabolized primarily by any single organ.
