MOVEMENT OF POTASSIUM AND SODIUM ACROSS MIDGUT EPITHELIUM OF AMERICAN COCKROACH

Atomic absorption spectrophotometry has been used to study movements of sodium and potassium across the midgut epithelium of the American cockroach. Movements of both ions are affected by the concentration and/or nature of the lumen contents. Generally, the net directional flow of potassium is from the blood-side to the lumen and is completely inhibited by 0·001 M dinitrophenol (DNP). Blood- and lumen-side DNP-sensitive mechanisms are transporting sodium, but the direction and existence of such movement appears to be dependent upon the nature of the lumen contents. Passive (non-DNP-sensitive) mechanisms appear to be quite important in controlling cation movements since passive diffusion cannot be demonstrated with corresponding increases in lumen sodium concentrations while in the presence of DNP. The sites of the various sodium and/or potassium transport mechanisms are discussed in relation to results obtained under numerous experimental conditions. © 1969.