Visualization of pH gradients in the larval midgut of Spodoptera litura using 31P-NMR microscopy

Abstract

Phosphorus NMR microscopy (scanning or imaging NMR) has been used noninvasively to measure the distribution of phosphate in the midgut of a lepidopteran larva, Spodoptera litura (Noctuidae). The technical background of the method is outlined and resolution to a pixel size of 0.39 mm 2 was obtained. It was demonstrated that there are both radial and longitudinal pH gradients within the digestive tract which are consistent with alkali production occurring in the midgut epithelium. The effects on the midgut pH distributions of a S. litura-active isolate of Bacillus thuringiensis endotoxin, and the antibiotics valinomycin and bafiiomycin also supported current theories on lepidopteran larval midgut alkali production.