Characteristics of putrescine uptake in isolated rat enterocytes

Polyamines are necessary for the growth of eukaryotic cells and are supplied either by new synthesis or cellular uptake. To our knowledge, no information is available on polyamine uptake by gastrointestinal cells. In the current study, isolated villous enterocytes from the rat accumulated putrescine to an eightfold concentration gradient. Uptake was temperature dependent, saturable, and inhibited by 1 mM KCN. Kinetic analysis showed a Km of 1.23 X 10(-5) M and a Vmax of 2.60 X 10(-10) mol.10(6) cells-1.15 min-1. Enterocytes from the distal one-fourth of the gut showed the highest rate of uptake. Putrescine uptake was inhibited by cadaverine and spermine but not by the amino acids asparagine, AIB, or leucine. Sodium replacement by choline, lithium, N-methyl-D-glucamine, or tetramethylammonium significantly inhibited uptake, but replacement of Na+ by sucrose or mannitol was without effect. The inhibition observed was believed to be due to the ability of the cations to interact in some way with the carrier. Neither ouabain nor digitoxigenin had any effect on uptake. These data indicate that putrescine is accumulated by villous enterocytes by a carrier-mediated process that does not appear to involve Na+ contransport.