Possible sodium and D-glucose cotransport in isolated jejunal epithelium of children.

Some experimental data in human jejunum suggest a Na dependence for glucose absorption and a glucose dependence for Na absorption. However, the relationship between these two transport processes is not yet known. Na+ and D-glucose absorptions were, therefore, measured simultaneously, in vitro, in isolated jejunal mucosa of children. The results are as follows: 1) the steady-state accumulation of D-glucose (C/M glucose) is a function of the Na concentration gradient between cell and medium (C/M Na). In Ringer solution, C/M glucose = 3.97 and C/M Na = 0.29; in the presence of 10(-4) M ouabain, C/M glucose = 1.63 and C/M Na = 0.60, and in Na free solution, C/M glucose = 0.99. In the presence of phloridzin, C/M Na is not statistically different from that in Ringer, but C/M glucose is significantly decreased. 2) The influx of D-glucose at the luminal membrane is a function of Na concentration in the bathing solution; it has the value of 4.41 mumole/hr cm2 in the presence of Na and of 1.65 mumole/hr cm2 in absence of Na. 3) The short-circuit current is a saturable function of D-glucose and of 3-O-D-methylglucose. The Kt for glucose is 8.01 mM. These results support the concept of a coupling between Na and D-glucose absorptions at the luminal membrane of jejunal mucosa of children.