The IGF-I axis in kidney and skeletal muscle of potassium deficient rats.
Potassium deficiency in the rat results in growth retardation, muscle wasting and renal hypertrophy. This study tests the thesis that K deficiency leads to tissue distinct changes in the local IGF-I system and cell sensitivity to IGF-I that favors renal enlargement on the one hand and impaired muscle growth on the other. In rats after eight days of K deficiency, compared to pair-fed control rats, food utilization and muscle and body wt gain were attenuated while the kidneys enlarged. In muscle GH receptor and IGF-I gene expression, IGF-I peptide and IGF binding protein-5 (IGFBP) levels were decreased. Together with reduced food utilization, these changes may contribute to the attenuated muscle growth. In the enlarged kidneys despite a fall in IGF-I mRNA level, IGF-I peptide concentration was increased more than twofold. This increase in IGF-I could be caused by the increase in kidney IGFBP-1 gene and protein expression and the decrease in kidney IGF-I degrading activity noted in K deficiency. Treatment with IGF-I failed to induce body or muscle growth, but induced a further increase in kidney size and enlargement of the spleen. Thus, in K deficiency the spontaneous increase in IGF-I levels in the kidney that is IGF-I sensitive may well be a cause of the renal hypertrophy.
Hsu
F W
FW
Department of Medicine, Stanford University, Palo Alto, California, USA.
Tsao
T
T
Rabkin
R
R
D000818:Animals; D000918:Antibody Specificity; D015153:Blotting, Western; D001835:Body Weight; D002462:Cell Membrane / Q000378:metabolism; D004435:Eating; D015870:Gene Expression / Q000502:physiology; D018970:Insulin-Like Growth Factor Binding Protein 1 / Q000235:genetics / Q000276:immunology; D007334:Insulin-Like Growth Factor I / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D007668:Kidney / Q000737:chemistry / Q000378:metabolism*; D008297:Male; D018482:Muscle, Skeletal / Q000737:chemistry / Q000378:metabolism*; D009929:Organ Size; D011188:Potassium / Q000097:blood; D011191:Potassium Deficiency / Q000378:metabolism*; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017207:Rats, Sprague-Dawley; D017526:Receptor, IGF Type 1 / Q000235:genetics / Q000378:metabolism; D011986:Receptors, Somatotropin / Q000235:genetics / Q000378:metabolism
D018970:Insulin-Like Growth Factor Binding Protein 1; D012333:RNA, Messenger; D011986:Receptors, Somatotropin; D007334:Insulin-Like Growth Factor I; D017526:Receptor, IGF Type 1; D011188:Potassium