Substance P receptors on canine chief cells: localization, characterization, and function.

Area of Science:

• Gastroenterology
• Neuroendocrinology
• Cell Biology

Background:

• Substance P is a neuropeptide involved in various physiological processes.
• The role of substance P in gastric mucosal function, particularly in chief cells, remains to be fully elucidated.

Purpose of the Study:

• To identify and characterize substance P binding sites in the canine gastric oxyntic mucosa.
• To determine the specific cell type expressing these binding sites.
• To investigate the functional consequence of substance P binding on chief cells.

Main Methods:

• Quantitative autoradiography on frozen canine stomach sections.
• Cell fractionation using centrifugal elutriation.
• Autoradiography on isolated gastric mucosal cells.
• Equilibrium binding analysis and competitive displacement studies.
• Measurement of pepsinogen secretion from isolated oxyntic glands.

Main Results:

• Saturable, high-affinity substance P binding sites were localized to chief cells in the canine oxyntic mucosa.
• Parietal and mucous cells did not exhibit substance P binding.
• Binding analysis revealed a single class of sites with Kd of 105 pM and Bmax of 3000 receptors/cell.
• Chief cells possess a substance P-preferring tachykinin receptor.
• Substance P stimulated pepsinogen secretion in a dose-dependent manner.

Conclusions:

• Canine gastric chief cells express specific, high-affinity substance P receptors.
• Substance P binding to chief cells is associated with the stimulation of pepsinogen secretion.
• These findings suggest a novel role for substance P in regulating gastric enzyme secretion.