Insulin and exercise stimulate muscle alpha-aminoisobutyric acid transport by a Na+-K+-ATPase independent pathway.
Sodium ions are required for the active transport of amino acids such as alpha-aminoisobutyric acid (AIB) into skeletal muscle. To examine the role of Na+-K+-ATPase in this phenomenon, studies were carried out using the isolated perfused rat hindquarter preparation. Perfusion for 30 min with ouabain at a dose sufficient to inhibit the Na+-K+ pump (10(-4) M) inhibited the basal rate of AIB uptake in all muscles studied by up to 80%. However, it failed to inhibit the stimulation of AIB uptake, either by insulin (200 microU/ml) or electrically-induced muscle contractions. The increase in K+ release by the hindquarter in the presence of ouabain was the same under all conditions suggesting comparable inhibition of the Na+-K+ pump. These studies suggest that the basal, but not insulin or exercise-stimulated AIB transport into muscle is acutely dependent on a functional Na+-K+ pump. They also suggest that stimulated and basal uptake of AIB involve different mechanisms.
Zorzano
A
A
Balon
T W
TW
Goodman
M N
MN
Ruderman
N B
NB
D000621:Aminoisobutyric Acids / Q000378:metabolism*; D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D005947:Glucose / Q000378:metabolism; D007328:Insulin / Q000494:pharmacology*; D007473:Ion Channels / Q000187:drug effects; D008297:Male; D009119:Muscle Contraction; D009132:Muscles / Q000201:enzymology / Q000378:metabolism*; D010042:Ouabain / Q000494:pharmacology; D005082:Physical Exertion; D051381:Rats; D011919:Rats, Inbred Strains; D012964:Sodium / Q000378:metabolism; D000254:Sodium-Potassium-Exchanging ATPase / Q000502:physiology
D000621:Aminoisobutyric Acids; D007328:Insulin; D007473:Ion Channels; C100049:2-aminoisobutyric acid; D010042:Ouabain; D012964:Sodium; D000254:Sodium-Potassium-Exchanging ATPase; D005947:Glucose