Influence of circulating insulin-like growth factor-I compared with that of intrarenal insulin-like growth factor-I on proximal nephron receptor density in rats.
1. We examined the effects of dietary protein manipulations in partially nephrectomized (one and one-third nephrectomy) and normal rats to gain perspective on the relative importance of circulating versus intrarenal (collecting tubule) insulin-like growth factor-I in the control of proximal nephron receptor density. In addition, we studied the factors that influence liver insulin-like growth factor-I secretion in partially nephrectomized rats. 2. Dietary protein restriction (6% versus 40%) lowered circulating levels of insulin and insulin-like growth factor-I in both normal and partially nephrectomized rats up to 3 weeks after institution of the diets; however, growth hormone levels were little changed. Reduced renal mass stimulated intrarenal production of insulin-like growth factor-I regardless of the diet. 3. Scatchard analysis revealed that the density of insulin-like growth factor-I receptors on glomerular and proximal tubule basolateral membranes increased when circulating levels of insulin-like growth factor-I were diminished, despite raised levels of intrarenal insulin-like growth factor-I, in partially nephrectomized rats. 4. Circulating insulin-like growth factor-I, rather than the tissue level, plays the dominant role in the control of proximal nephron receptor density under physiological conditions. Insulin, but not growth hormone, may play a role in liver insulin-like growth factor-I secretion in partially nephrectomized rats during dietary manipulations.
Hise
M K
MK
Department of Internal Medicine, University of Maryland Medical School, Baltimore.
Corteza
Q
Q
Klassen
D K
DK
Sadler
J H
JH
D000818:Animals; D002462:Cell Membrane / Q000378:metabolism; D004044:Dietary Proteins / Q000008:administration & dosage; D007334:Insulin-Like Growth Factor I / Q000032:analysis / Q000378:metabolism*; D007668:Kidney / Q000378:metabolism*; D008297:Male; D009392:Nephrectomy; D009399:Nephrons / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D017451:Receptors, Somatomedin / Q000378:metabolism*
D004044:Dietary Proteins; D017451:Receptors, Somatomedin; D007334:Insulin-Like Growth Factor I