Figure 1.

Cannabinoid CB₁ receptors are present in parietal cells of the human gastric mucosa. (A) Immunohistochemical localization of CB₁ receptors in selective cells of human gastric glands. Note that only a small number of glandular cells show strong immunoreactivity for CB₁ receptors. These cells exhibit a large-sized, centered nucleus, and the staining is restricted to cytoplasmic and membrane regions. (B) Representative Western blot of a donor in which gastric samples from corporal (left lane) and antral mucosa (right lane) were used. Note the intense 60-kDa band on the samples from corporal mucosa (a region known to contain high amounts of acid-secreting parietal cells) compared with the almost absent band on samples from the antral region (known to be devoid of this type cell). (C,D) Confocal images showing immunofluorescent colocalization of CB₁ immunoreactivity (C) and H⁺/K⁺ ATPase immunoreactivity (D) in human biopsies of gastric mucosa. As expected, CB₁ receptors exhibit a membrane and cytoplasmic distribution, whereas the transporter is limited to cytoplasmic vesicles. Note the match between cells expressing both phenotypic markers (merged image, E) that indicate that parietal cells are the only cell type of the gastric mucosa expressing cannabinoid CB₁ receptors. Markers for other cell populations of the human gastric mucosa showed no colocalization with CB₁ receptors (data not shown). Bars: A = 100 μm; C–E = 50 μm.