ABSORPTION OF MIXTURES OF SUGARS BY ISOLATED SURVIVING GUINEA PIG INTESTINE

Abstract

In the presence of mixtures of glucose and fructose, at a concentration of, or below, 14 mM, additive rates of sugar transport by the isolated surviving guinea pig intestine are found. At a concentration of 28 mM, or above, the rate of transport of glucose is maximum and no additive rates with mixtures of glucose and fructose at such concentrations are obtained. The rate of transport of sugar from the intestine in the presence of sucrose is that to be expected from the hydrolysis of sucrose to glucose and fructose in the intestine. The increase of concentration of potassium ion to 15.6 meq./liter accelerates the rate of sugar transport from sucrose as well as from, glucose–fructose mixtures. The rate of galactose transport by the isolated surviving guinea pig intestine is inhibited 80% in the presence of an equivalent concentration (14 mM) of glucose. Fructose, at this concentration, has no inhibitory effect on the rate of galactose transport. Mannose (14 mM) and D-glucosamine (14 mM) effect 30% inhibitions of galactose transport. Sucrose (14 mM) is highly inhibitory (67%) to galactose transport, this probably being due to glucose formation in the intestine. Lactose (14 mM) is also apparently inhibitory (46%) to galactose transport, but it is possible that this inhibition is partly due to isotopic dilution by galactose obtained by lactose breakdown. These results are discussed in relation to the phosphorylation hypothesis of sugar transport in the intestine.