AJP - Renal Physiology, Vol 260, Issue 2 243-F248, Copyright © 1991 by American Physiological Society
Isolation of nephrocalcin from kidney tissue of nine vertebrate species
Y. Nakagawa, C. L. Renz, M. Ahmed and F. L. Coe
Nephrology Program, University of Chicago, Illinois 60637.
Nephrocalcin (NC), a urinary calcium oxalate monohydrate (COM) crystal
growth inhibitor, was purified from kidneys of nine vertebrate species
including humans. All isolates were glycoproteins with high contents of
aspartic and glutamic acids and small amounts of basic and aromatic amino
acids. Carbohydrate contents ranged from 4 to 16 wt% among the different
species, but all contained fucose, mannose, galactose, glucose,
galactosamine, glucosamine, and N-acetylneuraminic acid. Although amino
acid and carbohydrate compositions were similar, dissociation constants
derived from calcium oxalate monohydrate inhibition varied between 10(-7)
and 10(-8) M, and highest affinity could be related to highest ability of
the kidney of origin to concentrate urine. Using an antibody raised against
NC from human kidney tissue culture medium, we found strong
immunoreactivity with two species, pigs and sheep. Thus far all vertebrate
kidneys possess COM growth-inhibiting material that seems to be of
glycoprotein character, and all the glycoproteins isolated so far share
similar features, suggesting NC-like proteins are a well-conserved trait.
