The gastric mucosa secretes a number of substances, including acid, mucus, hormones, and proteases. Parietal cells are responsible for the release of hydrochloric acid into the deep plasma membrane invaginations known as canaliculi. The acid, which helps break down ingested material, is so strong that it could easily eat through wood. Gastrin, a hormone secreted by the g-cells of the mucosa, is primarily responsible for the regulation of the parietal cells’ acid secretion. The inactive precursor to pepsin, pepsinogen, is secreted by mucus cells and chief cells. It is converted to pepsin, which hydrolyses peptide bonds and initiates protein disassembly, when mixed with hydrochloric acid in the stomach. The mucus secreted by cells in the gastric epithelium is rich in bicarbonate and protects the stomach from being harmed by the hydrochloric acid it contains.

In order to localize a red fluorescent tag to F-actin in the sample of rat stomach tissue presented in the digital image above, the specimen was labeled with Alexa Fluor 568 conjugated to a phallotoxin (phalloidin). Oregon Green 488 conjugated to the lectin wheat germ agglutinin, which selectively binds to N-acetylglucosamine and N-acetylneuraminic residues, was also applied to the tissue sample, as was the nuclear counterstain Hoechst 33342. Images were recorded in grayscale with a 12-bit digital camera coupled to a Nikon Eclipse 80i microscope equipped with bandpass emission fluorescence filter optical blocks. During the processing stage, individual image channels were pseudocolored with RGB values corresponding to each of the fluorophore emission spectral profiles.