L-Lactate and D-Lactate carriers on the fetal and the maternal side of the trophoblast in the isolated guinea pig placenta.
The transfer of 14C-labelled D- or L-lactate (test substance) relative to 3H-L-glucose (control substance, extracellular marker) into the trophoblast of the isolated guinea pig placenta was determined during an open loop perfusion on both sides. Using a single passage, paired tracer dilution technique, the maximal lactate uptake (Umax) was derived from the venous concentration ratio of lactate to L-glucose. A significant metabolism of L-lactate was not observed. The lactate uptake, which occurred in all placentas studied, was not significantly different on the fetal and maternal side. Within one placenta the L-lactate uptake was always higher than the D-lactate uptake. The uptake of both L- and D-lactate could be inhibited by phloretin. The lactate uptake was inversely correlated with the pH of the perfusate fluid within the range from 6.2-8. A first order saturation kinetic (Hofstee-plot) was used to approximate the relationship between the L-lactate uptake and the chemical L-lactate concentration. We conclude that similar lactate carriers exist in the membranes on both the maternal and the fetal side of the trophoblast.
D000818:Animals; D005260:Female; D006168:Guinea Pigs; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D007773:Lactates / Q000378:metabolism*; D019344:Lactic Acid; D010693:Phloretin / Q000494:pharmacology; D010920:Placenta / Q000378:metabolism*; D011247:Pregnancy; D013237:Stereoisomerism; D014327:Trophoblasts / Q000378:metabolism*
D007773:Lactates; D019344:Lactic Acid; D010693:Phloretin