Distribution of chemical elements in the cellular and extracellular components of the stomach and duodenum of rats

Abstract

Electron-probe x-ray microanalysis was performed on freeze-dried sections, 4 μm in thickness, of the walls of the stomach and duodenum of Sprague-Dawley rats by using a scanning electron microscope equipped with an energy dispersive x-ray detector and a pulse-height analysis system. Comparable cellular and extracellular components, i.e., the luminal epithelium, lamina propria, muscularis mucosae, submucosa, tunica muscularis, and serosa of the stomach and duodenum were probed with an electron beam using an acceleration voltage of 15 kV. This results in the emission of x-rays that are characteristic of the elements present in the volume probed. Six elements of biologic interest were detected, specifically Na, Mg, P, S, Cl, and K. Based on the peak /continuum ratios for these elements, relative concentrations were measured for each of the probe sites. The findings indicate significant differences exist between the relative amounts of Na (P < 0.01) and Cl (P < 0.001) in the submucosae of the stomach and duodenum. Also, between successive layers of the walls of the stomach and duodenum there are apparent differences in the relative concentrations of certain elements. Concentration gradients for Na, Cl, K, and P are apparent between the mucosal and serosal surfaces of these organs. Other elemental concentration and gradient differences are seen between and within the walls of the stomach and duodenum. Furthermore, these studies indicate that different cellular and extracellular probe sites in the stomach and duodenum show different spectral profiles due to subtle differences in peak intensities of the various elements. The findings of the present study suggest that electron-probe x-ray microanalysis might provide useful information on the relative distribution and concentration of chemical elements concerned with the physiologic processes of the gastrointestinal tract.