AJP - Endocrinology and Metabolism, Vol 256, Issue 2 E208-E214, Copyright © 1989 by American Physiological Society
Insulin degradation products from perfused rat kidney
W. C. Duckworth, F. G. Hamel, J. Liepnieks, D. Peavy, B. Frank and R. Rabkin
Veterans Administration Medical Center, Omaha, Nebraska.
The kidney is a major site for insulin metabolism, but the enzymes involved
and the products generated have not been established. To examine the
products, we have perfused rat kidneys with insulin specifically iodinated
on either the A14 or the B26 tyrosine. Labeled material from both the
perfusate and kidney extract was examined by Sephadex G50 and
high-performance liquid chromatography (HPLC). In perfusate from a
filtering kidney, 22% of the insulin-sized material was not intact insulin
on HPLC. With the nonfiltering kidney, 10.6% was not intact insulin.
Labeled material from HPLC was sulfitolyzed and reinjected on HPLC. By use
of 125I-iodo(A14)-insulin, almost all the degradation products contained an
intact A-chain. By use of 125I-iodo(B26)-insulin, several different
B-chain-cleaved products were obtained. The material extracted from the
perfused kidney was different from perfusate products but similar to
intracellular products from hepatocytes, suggesting that cellular
metabolism by kidney and liver are similar. The major intracellular product
had characteristics consistent with a cleavage between the B16 and B17
amino acids. This product and several of the perfusate products are also
produced by insulin protease suggesting that this enzyme is involved in the
degradation of insulin by kidney.
