Characterization of the effect of cocaine on catecholamine uptake by pregnant myometrium.

OBJECTIVE

To characterize the effect of cocaine on catecholamine uptake by myometrium from pregnant women.

METHODS

Slices of myometrium obtained from nine women during elective cesarean delivery at term were incubated with [3H]-norepinephrine and various uptake inhibitors for 30 minutes. The radiolabeled material was extracted with perchloric acid, expressed as percent control (+/- standard error of the mean), and compared by one-factor analysis of variance and Fisher multiple range test.

RESULTS

Myometrial uptake was inhibited by cocaine (42 +/- 9%) by neuronal (type 1) uptake inhibitors (desipramine 41 +/- 14%; N-ethylmaleimide 53 +/- 8%), and by extraneuronal (type 2) inhibitors (normetanephrine 56 +/- 19%; corticosterone 73 +/- 9%). When uptake inhibitors were used in combination with cocaine, uptake was not decreased further in the presence of neuronal inhibitors (desipramine plus cocaine 40 +/- 20%; N-ethylmaleimide plus cocaine 42 +/- 4%). However, the effect of cocaine appeared to be added to that of extraneuronal inhibitors (normetanephrine plus cocaine 25 +/- 14%; corticosterone plus cocaine 32 +/- 1%).

CONCLUSION

Catecholamine uptake by myometrium in pregnant women appears to be both extraneuronal and neuronal in nature, and cocaine inhibits the neuronal portion of this uptake. This mechanism may play a role in the increased rate of premature delivery associated with cocaine abuse.