LACK OF EFFECT OF COCAINE ON LYSINE AND ALANINE UPTAKE IN HUMAN PLACENTAL VILLI OR TRANSFER IN PERFUSED HUMAN PLACENTA

The effect of cocaine on lysine and alanine uptake in human placental villi and transfer across the dually perfused placenta was studied. Up take ( in terms of the intracellular to extracellular distribution rat io) of alanine and lysine was 2.81+/-0.30 (n = 5) and 1.45+/-0.24 (n = 5) respectively and was unaffected by cocaine (50-500 ng mL(-1)) in t he incubation medium. In the dually perfused placenta, the clearance i ndex (ratio of amino acid to antipyrine clearance) was 0.35+/-0.03 and 0.30+/-0.05 and the transfer index (ratio of amino acid to L-glucose clearance) was 2.20+/-0.07 and 1.89+/-0.29 for lysine and alanine resp ectively. Cocaine at concentrations of 100 ng mL(-1) or 250 ng mL(-1) had no effect on the clearance of either amino acid. The results of th is study indicate that concentrations of cocaine likely to be encounte red in vivo do not affect uptake of lysine or alanine by placental vil li or transfer across the perfused placental lobule, in contrast with the report that cocaine reduces uptake of alanine by placental vesicle s, Experimental models must be critically evaluated before accepting t he results as pertinent to a clinical situation.