Glutamine transport and metabolism in denervated rat skeletal muscle.
Rat skeletal muscle glutamine fell by 40% from 4.18 to 2.5 mumols/g wet weight (P less than 0.01) after 4 days of denervation. Over the same period net glutamine efflux from denervated hindlimbs [i.e., arteriovenous (a-v) concentration differences x blood flow] increased 3.5-fold (from -6.72 +/- 1.73 to -26 +/- 4.81 nmol.min-1.g-1, P less than 0.001). Gastrocnemius glutamine synthetase activity fell 48% after denervation (from 475 +/- 81 to 248 +/- 39 nmol.min-1.g-1, P less than 0.001), but glutaminase activity was not significantly altered (17 nmol.min-1.g-1). The maximal activity (Vmax) of the unidirectional Na(+)-dependent glutamine transporter (system Nm) was depressed by 45% from 1,020 +/- 104 to 571 +/- 9 nmol.min-1.g-1 (P less than 0.01), but the concentration at which transport was half maximal (Km) was not significantly altered (control 8.1 +/- 0.6 mM; denervated 6.52 +/- 0.12). Hindlimb denervation resulted in an increase of intramuscular Na+ by 17% and a fall of K+ by 12%, and the resting membrane potential in isolated muscles decreased from -75 +/- 10 to -59.5 +/- 5.5 mV. Membrane potential of perfused denervated muscle, isolated after acute addition of the Na+ channel blocker tetrodotoxin (TTX, 3 microM), repolarized to -66.4 +/- 3.2 mV. In perfused denervated preparations TTX caused an acute recovery of Vmax of unidirectional glutamine transport to 848 +/- 75 nmol.min-1.g-1; Km was unaffected.(ABSTRACT TRUNCATED AT 250 WORDS)
Hundal
H S
HS
Department of Anatomy and Physiology, University of Dundee, United Kingdom.
Babij
P
P
Watt
P W
PW
Ward
M R
MR
Rennie
M J
MJ
D000818:Animals; D005260:Female; D005973:Glutamine / Q000097:blood / Q000378:metabolism*; D007700:Kinetics; D008564:Membrane Potentials; D009121:Muscle Denervation; D009132:Muscles / Q000098:blood supply / Q000294:innervation / Q000502:physiology*; D051381:Rats; D011919:Rats, Inbred Strains; D012016:Reference Values; D012039:Regional Blood Flow
D005973:Glutamine