MOVEMENT OF CALCIUM AND MAGNESIUM ACROSS MIDGUT EPITHELIUM OF AMERICAN COCKROACH

Atomic absorption spectrophotometry has been used to study net movements of calcium and magnesium across the midgut epithelia of the American cockroach. Movements of both ions are affected by the concentration of midgut lumen contents. Generally, influx movements of both ions are decreased with increasing lumen osmolality. DNP (2,4-dinitrophenol, 0·001 M) tends to increase the influx of calcium while the inverse in true for magnesium. Only minimal quantities of dinitrophenol are absorbed into the epithelial cells, and only a small fraction of this completely crosses the epithelial cells during the course of the 2 hr experiment. These data and an indication that dinitrophenol placement (lumen or blood side) is correlated with resultant changes in ion movements suggest that the primary effect of dinitrophenol is on or near the epithelial membrane. © 1969.