Sugar Transport from the Lumen of the Rat Uterus

Abstract

Selective luminal perfusion was utilized to characterize a sugar transport mechanism on the uterine surface in estrogen primed ovariectomized adult rats. After a 30 s luminal perfusion/incubation with a dual label system (10 .mu.Ci/ml at 1.0 mM final concentration of each compound), ethanol extractable [14C]-D-mannitol and [3H]-3-O-methyl-D-glucose (3-O-MG) were employed to estimate diffusion and total sugar uptake, respectively. The transport component of [3H]-3-O-MG uptake was calculated as the difference between these 2 parameters. The carrier mechanism for 3-O-MG was observed to move the sugar faster than by diffusion, was inhibited by D-glucose (but not by D-fructose or D-mannitol) and was insensitive to ouabain. This sugar uptake mechanism is probably one of facilitative transport. The interaction between amino acid (.alpha.-aminoisobutyric acid = AIB) and sugar transport also was studied. Whereas AIB exerted no effect on [3H]-3-O-MG transport, high concentrations of 3-O-MG stimulated AIB transport, inhibition of efflux resulting in apparent stimulation of influx. Since D-glucose did not exert a similar effect, the mechanism of 3-O-MG inhibition was considered an interference with D-glucose utilization by metabolic enzymes and, hence, an indirect effect on the energy dependent AIB efflux transport step.