Effects of IGF-I infusion on growth and muscle Na(+)-K+ pump concentration in K(+)-deficient rats.
K(+)-deficient rats and control rats were infused for 14 days with vehicle: acetic acid (AcA) or recombinant human insulin-like growth factor-I (IGF-I, 240 micrograms/day) by osmotic minipumps. IGF-I treatment of K(+)-deficient rats did not result in overall growth of carcass or muscles but in marked selective growth of adrenals (+42%) and spleen (+66%). In control rats, IGF-I induced increased body and muscle weight, tibia length, and thymus weight. K+ deficiency was associated with reduced serum IGF-I but unchanged thyroid status. IGF-I treatment of the K(+)-deficient rats restored serum IGF-I and decreased total 3,5,3'-triiodothyronine. In AcA-treated K(+)-deficient rats [3H]ouabain binding site concentration decreased by 63 and 43% in soleus and extensor digitorum longus (EDL) muscle, respectively, compared with the AcA-treated controls. IGF-I had no effect on the [3H]ouabain binding site concentration in the control group, but in K(+)-deficient rats a significant lowering of 26% was observed in EDL. K+ deficiency causes relative organ-specific resistance to the growth-promoting effects of IGF-I, comparable to the effects seen in protein-restricted rats. Reduced circulating IGF-I is not the only cause of the downregulation of Na(+)-K+ pumps in K+ deficiency, and IGF-I treatment of control animals in vivo has no stimulatory effect on the synthesis of Na(+)-K+ pumps.
Dørup
I
I
Institute of Physiology, University of Aarhus, Denmark.
Flyvbjerg
A
A
D000311:Adrenal Glands / Q000187:drug effects / Q000254:growth & development; D000818:Animals; D001665:Binding Sites; D001835:Body Weight / Q000187:drug effects; D001846:Bone Development / Q000187:drug effects; D005260:Female; D006128:Growth / Q000187:drug effects*; D007262:Infusions, Intravenous; D007334:Insulin-Like Growth Factor I / Q000008:administration & dosage / Q000494:pharmacology*; D007700:Kinetics; D024510:Muscle Development; D009132:Muscles / Q000187:drug effects / Q000378:metabolism*; D009929:Organ Size / Q000187:drug effects; D010042:Ouabain / Q000378:metabolism; D011191:Potassium Deficiency / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D012016:Reference Values; D000254:Sodium-Potassium-Exchanging ATPase / Q000187:drug effects* / Q000502:physiology; D013154:Spleen / Q000187:drug effects / Q000254:growth & development; D013950:Thymus Gland / Q000187:drug effects / Q000254:growth & development; D013997:Time Factors; D015430:Weight Gain / Q000187:drug effects
D010042:Ouabain; D007334:Insulin-Like Growth Factor I; D000254:Sodium-Potassium-Exchanging ATPase