The effects of phlorizin,phloretin and ouabain on the reabsorption of glucose by the Malpighian tubules of Locusta migratoria migratorioides

Isolated Malpighian tubules of Locusta reabsorb significant levels of glucose from their lumen back into the bathing fluid (haemolymph). This reabsorption is inhibited by phlorizin, phloretin and ouabain. Both phlorizin and phloretin are found to accumulate in the secreted fluid of the tubules against concentration gradients. Ouabain inhibition is explained in terms of its effect on intracellular Na⁺ concentrations. A hypothetical model of the role that Na⁺ may play in glucose reabsorption is presented as a possible explanation of these observations.