Wortmannin inhibits both insulin- and contraction-stimulated glucose uptake and transport in rat skeletal muscle.
The role of phosphatidylinositol (PI) 3-kinase for insulin- and contraction-stimulated muscle glucose transport was investigated in rat skeletal muscle perfused with a cell-free perfusate. The insulin receptor substrate-1-associated PI 3-kinase activity was increased sixfold upon insulin stimulation but was unaffected by contractions. In addition, the insulin-stimulated PI 3-kinase activity and muscle glucose uptake and transport in individual muscles were dose-dependently inhibited by wortmannin with one-half maximal inhibition values of approximately 10 nM and total inhibition at 1 microM. This concentration of wortmannin also decreased the contraction-stimulated glucose transport and uptake by approximately 30-70% without confounding effects on contractility or on muscle ATP and phosphocreatine concentrations. At higher concentrations (3 and 10 microM), wortmannin completely blocked the contraction-stimulated glucose uptake but also decreased the contractility. In conclusion, inhibition of PI 3-kinase with wortmannin in skeletal muscle coincides with inhibition of insulin-stimulated glucose uptake and transport. Furthermore, in contrast to recent findings in incubated muscle, wortmannin also inhibited contraction-stimulated glucose uptake and transport. The inhibitory effect of wortmannin on contraction-stimulated glucose uptake may be independent of PI 3-kinase activity or due to inhibition of a subfraction of PI 3-kinase with low sensitivity to wortmannin.
Copenhagen Muscle Research Centre, August Krogh Institute, University of Copenhagen, Denmark.
J F
JF
Wojtaszewski
B F
BF
Hansen
B
B
Ursø
E A
EA
Richter
D019870:1-Phosphatidylinositol 4-Kinase; D000255:Adenosine Triphosphate / Q000378:metabolism; D000730:Androstadienes / Q000494:pharmacology*; D000818:Animals; D004558:Electric Stimulation; D005947:Glucose / Q000378:metabolism*; D006614:Hindlimb / Q000378:metabolism; D007004:Hypoglycemic Agents / Q000037:antagonists & inhibitors* / Q000494:pharmacology; D007329:Insulin Antagonists / Q000494:pharmacology*; D008297:Male; D008566:Membranes / Q000187:drug effects / Q000378:metabolism; D009119:Muscle Contraction / Q000502:physiology; D018482:Muscle, Skeletal / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D010101:Oxygen Consumption / Q000502:physiology; D010725:Phosphocreatine / Q000378:metabolism; D010766:Phosphorylation; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D011972:Receptor, Insulin / Q000378:metabolism; D000077191:Wortmannin
D000730:Androstadienes; D007004:Hypoglycemic Agents; D007329:Insulin Antagonists; D010725:Phosphocreatine; D000255:Adenosine Triphosphate; D017853:Phosphotransferases (Alcohol Group Acceptor); D019870:1-Phosphatidylinositol 4-Kinase; D011972:Receptor, Insulin; D005947:Glucose; D000077191:Wortmannin