L-lactate uptake by rat liver. Effect of food deprivation and substrate availability.
We have studied the role of substrate availability on net L-lactate uptake by liver of anaesthetized fed and 24 h-fasted rats. L-Lactate was infused through a mesenteric vein at infusion rates equivalent to 0, 0.125, 0.25 and 0.5 times the basal turnover rate (Rt). By these means we were able to increase L-lactate portal concentrations up to 5.5 mM, without significant changes in portal pH. In the basal state (0 Rt), a net L-lactate uptake by liver was found in 24 h-fasted animals. No net balance was observed in fed rats. Infusion of L-lactate in fed animals failed to induce a net hepatic uptake, except when L-lactate levels in portal vein were raised above 5 mM. In fasted animals, net L-lactate uptake by liver increased linearly (r = 0.99) as a function of L-lactate concentration in the portal vein, even beyond the saturation of its specific carrier. It is concluded that, first, the L-lactate carrier does not limit net L-lactate uptake, and second, that substrate availability is an important factor modulating net L-lactate uptake by liver.
Felipe
A
A
Departament de Bioquímica i Fisiologia, Universitat de Barcelona, Spain.
Remesar
X
X
Pastor-Anglada
M
M
D000818:Animals; D005260:Female; D005508:Food Deprivation; D007773:Lactates / Q000097:blood / Q000378:metabolism*; D019344:Lactic Acid; D008099:Liver / Q000378:metabolism*; D011773:Pyruvates / Q000097:blood; D019289:Pyruvic Acid; D051381:Rats; D011919:Rats, Inbred Strains; D013379:Substrate Specificity
D007773:Lactates; D011773:Pyruvates; D019344:Lactic Acid; D019289:Pyruvic Acid