Wg. Aschenbach et al., Effect of a myocardial volume overload on lactate transport in skeletal muscle sarcolemmal vesicles, AM J P-REG, 281(1), 2001, pp. R176-R186
Citations number
44
Categorie Soggetti
Physiology
Journal title
AMERICAN JOURNAL OF PHYSIOLOGY-REGULATORY INTEGRATIVE AND COMPARATIVE PHYSIOLOGY
This study sought to determine the effect of a myocardial volume overload (
MVO) on sarcolemmal (SL) lactate (La-) transport and the aerobic profile of
skeletal muscle. SL vesicles were obtained from female rats 10 wk after ei
ther a MVO was induced by creation of an infrarenal fistula (n = 10), or sh
am surgeries were performed (n = 11). Influx of C-14-labeled L(+)-La- was m
easured at various unlabeled La- concentrations under zero-trans conditions
. La- transport kinetics were determined using a Michaelis-Menten equation
with an added linear component to discriminate between carrier-mediated and
diffusional transport. Although heart and lung weights were significantly
increased (P < 0.0001) in the MVO group, left ventricular function was only
modestly altered (P < 0.05). A significant reduction in type I myosin heav
y chain (MHC) in the soleus and a strong trend (P = 0.06) for a reduced typ
e IIx MHC in the plantaris were observed in MVO rats, but no differences in
citrate synthase activity or monocarboxylate transporter proteins (MCT)-1
expression were noted in any muscle. Carrier-mediated La- influx into SL ve
sicles was similar between sham and MVO (K-m =12 +/- 1 and 18 +/- 3 mM; app
arent V-max = 772 +/- 99 and 827 +/- 80 nmol.mg(-1).min(-1), respectively).
Total influx at 100 mM was lower in MVO, and this was due to a 30% reducti
on in membrane diffusion. In conclusion, a 10-wk MVO did not alter MCT-medi
ated La- transport or protein expression but was associated with modest cha
nges in myofibrillar proteins and impaired SL diffusive properties.