Relation of Kidney Tissue Somatomedin-C/Insulin-Like Growth Factor I to Postnephrectomy Renal Growth in the Rat*

Abstract

In kidney tissue extracts, we observed elevated somatomedin-C (SmC) tissue concentrations in the kidney remaining after nephrectomy compared to those in the kidney removed at surgery or kidneys from sham-operated animals. In hypophysectomized animals, we observed a response of the same magnitude, but from significantly lowered basal SmC concentrations. In neither case did nephrectomy affect SmC levels in serum or other tissues studied (liver and lung). The increased tissue levels of SmC in the regenerating kidney, with a return to baseline levels within 30 days, along with the absence of elevated serum levels suggest a local role for this mitogen in organ growth.

Insulin-like growth factor I gene expression in isolated rat renal collecting duct is stimulated by epidermal growth factor.

“…In addition to hypersomatotropism (14), levels of IGF I in whole kidney (3)(4)(5) and collecting duct (15,16) are increased in compensatory renal hypertrophy (3,15,16) and in diabetic renal hypertrophy (4,5). The changes in renal IGF I gene expression in compensatory hypertrophy and diabetes cannot be attributed to GH, since renal IGF I is elevated in compensatory hypertrophy in hypophysectomized rats (3) and since levels of circulating GH are reduced in diabetic rats (6). Therefore, it is likely that stimuli other than GH regulate IGF I gene expression in kidney in one or both of these conditions and in other settings.…”

Expression of liver insulin-like growth factor 1 gene and its serum level in rats with diabetes

“…The homogenates were extracted with 1 mmol·L -1 acetic acid (precooled) and centrifuged. The supernatants were collected, then mixed with 0.05 mmol·L -1 Tris·HCl (PH 7.8) to neutralization and finally stored under -70 for future use [10] . An aliquot of the samples treated as above was taken to measure both total protein content by Brodford method and IGF-1 peptide concentration by enzyme linked immunosorbent assay (ELISA, Diagnostic Systems Laboratory, Inc.).…”

Effects of recombinant human insulin-like growth factor I on glomerular dynamics in the rat.

“…IGF-I receptors have been demonstrated in cultured glomerular mesangial cells, proximal tubular epithelial cells, vascular endothelial cells, and vascular smooth muscle cells (8-1 1). In rats, the kidney IGF-I content increases during compensatory renal hypertrophy (5,(12)(13)(14), with feeding of high protein diets that promote renal hypertrophy ( 14), and during recovery from acute renal ischemic injury (15). Growth hormone injections, which also cause renal hypertrophy, also increase renal IGF-I levels ( 16).…”