Resolution of the potassium pool size controversy in insect midgut

Abstract

The isolated midgut of Lepidopteran larvae actively transports potassium from the hemolymph side to the lumen side when chamber-mountedin vitro. Active potassium transport is not affected by ouabain and is not dependent on sodium. A long controversy has existed over the fraction of the midgut cells that participate in active transport of potassium. One set of investigators demonstrated that only a small fraction of the tissue potassium was involved in the pool of potassium involved in active transport whereas a separate set of workers found that virtually all of the exchangeable potassium was thus involved. The results presented in this paper show that the insect's diet affects whether some or all the cells are in the pool, known formally as a transport pool. Leaf-reared insects are characterized by a small pool whereas diet-reared insects are characterized by a large pool. These results are shown to correlate with the pool size results of previous investigators.