Hexose transport by hamster intestine in vitro.

INGS MESON. Hexose transport by hamster intestine in vitro. Am. J. Physiol. 203(2): 237-240. Ig62.-The ability of everted sacs of hamster intestine to concentrate 18 glycosides and 5-deoxyglucose was determined. It was concluded that most of the glycosides were actively transported, but the nature of the aglycone is an important determinant in the extent of transport. A pyranose configuration is required of a sugar if it is to be transported. Evidence was also obtained which indicates that the carbon-to-hydrogen bonds of carbon I and 6 of glucose are transported intact. Therefore, the occurrence during transport of a reaction in which either of these bonds is cleaved appears unlikely. C ONSIDERABLE DATA bearing upon the specificity and mechanism of hexose transport by the intestine are now available. Structural requirements for active sugar transport by the intestine of the hamster have been partially established (I, 2) and evidence has been presented which appears to exclude phosphorylation from direct participation in the transport mechanism (3, 4). These observations have now been extended. First, the restrictions which limit active transport of compounds differing from glucose and galactose by the modification of the carbon I grouping have been investigated by a study of a series of glycosides. Secondly, the availability of 5-deoxyglucose has permitted a test of the specificity of transport for a hexose differing in structure from glucose at carbon 5. Finally, the use of glucose labeled with tritium has permitted a determination of whether or not reactions involving the rupture of the bonds between the hydrogens and carbon I or 6 of glucose participate in the mechanism of active transport. This is Received for publication 29 December 1961. especially to be considered with regard to carbon 6 since hexoses, but not pentoses, are transported against a concentration gradient (5). The glycosides and 5-deoxyglucose were tested for transport in an everted sac preparation from hamster intestine in the manner previously described (6). For the mucosal solution 3.0 ml of modified Krebs-Henseleit-medium containing the sugar to be tested was used and 1.0 ml was introduced into the sac. Only small changes in the volume in the sacs were observed at the completion of incubation. Glycoside concentrations were usually determined by Nelson's copper reduction methad after hydrolysis of a Ba(OH)2-ZnS04 filtrate (7) of the sugar solution in I N HCl at I oo C for 1-2 hr, and subsequent neutralization with NaOH. In some experiments an …