ISSN:
1432-2013
Keywords:
Maternofetal exchange
;
Placenta
;
Permeability
;
l-lactate
;
Mediated transport
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Abstract In the guinea-pig placenta which was artificially perfused on the fetal side while maternal placental blood flow was controlled, the placental transfer per mean transplacental concentration difference (the transfer coefficient TC) was determined for lactate. TC forl-lactate (TCLL) was compared to that ford-lactate (TCDL) and measured for various concentrations ofl-lactate, bicarbonate, pyruvate and CO2. Applying a “closed circuit” perfusion technique,l-lactate and proton concentrations on both sides of the placenta were followed during infusion of HCl and sodiuml-lactate into the fetal circulation. It was found that TCLL is 3 times TCDL. TCLL is depressed by increasing concentrations ofl-lactate while TC for Cl-36 is not. TCLL is also depressed by 50 mmol·l−1 pyruvate. Concentration changes of glucose do not affect TCLL. TCLL rises with the proton concentration, independently of the concomitant changes of the bicarbonate concentration. Transplacentral proton concentration gradients producel-lactate concentration gradients and vice versa. It is concluded that (1) facilitated diffusion ofl-lactate occurs in the placenta and that (2)l-lactate transfer is coupled with proton transfer. Beside the well-known placental transport system for glucose this is the second passive transport system found in a placenta.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00647462
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