Renal insulin-like growth factor (IGF)-I expression is enhanced in tis
sue that remains following removal of kidney mass. To characterize the
expression of renal IGF-I after reduction of kidney mass by partial u
nilateral infarction, we measured levels of IGF-I extracted from nonin
farcted (remnant) renal tissue that remained after one-half unilateral
kidney infarCtion that was performed without (1/2NX) or with (1 1/2NX
) contralateraL nephrectomy. Levels of IGF-I extracted from remnant re
nal tissue after 1/2NX increased significantly, peaking on day 3 after
renal mass reduction, and then returned toward baseline. Steady-state
levels of IGF-I MRNA were also elevated on day 3, suggesting that the
increase in IGF-I results from enhanced synthesis. A simiLar pattern
of increased extracted IGF-I and elevated IGF-I MRNA occurred after 1
1/2NX. Levels of IGF-I extracted from remnant renal tissue 3 days afte
r 1 1/2NX were not higher than leveLs extracted from remnant tissue 3
days after 1/2NX, and both were higher than levels of IGF-I extracted
from contralateral kidneys 3 days after unilateral nephrectomy. Theref
ore, Levels of IGF-I did not correlate with the extent of reduction of
renal mass per se. We conclude that partial renal infarction provides
a stimulus to enhance IGF-I expression. Increased renal IGF-I must be
considered in the interpretation of findings originating from use of
remnant kidney models of chronic renal failure.