Journal of Neuroscience, Vol 9, 2878-2886, Copyright © 1989 by Society for Neuroscience
Substance P receptors on canine chief cells: localization, characterization, and function
SR Vigna, CR Mantyh, AH Soll, JE Maggio and PW Mantyh
Department of Medicine, UCLA School of Medicine 90024.
Saturable binding sites for 125I-Bolton-Hunter substance P were observed in
frozen sections of the oxyntic mucosa of the canine stomach using
quantitative autoradiography. The cell type possessing substance P binding
sites in this region was identified as the chief cell in 2 ways. First, the
saturable binding of radioiodinated substance P correlated with chief cell
content (and not with parietal cell content, for example) in dispersed
oxyntic mucosal cells fractionated by centrifugal elutriation. Second,
saturable binding of radioiodinated substance P was localized to dispersed
chief cells by autoradiography using emulsion-coated preparations of
isolated cells affixed to glass slides. Parietal and mucous cells did not
bind substance P. In studies of enriched chief cell preparations, the
binding of radiolabeled substance P was found to be time- and cell
number-dependent, specific, saturable, reversible, and of high affinity.
Equilibrium binding analysis revealed a single class of binding sites with
an apparent Kd of 105 pM and a Bmax of 3000 receptors per cell. In
competitive displacement studies, the order of potency of analogs for
inhibition of the saturable binding of radiolabeled substance P to chief
cells was substance P = physalaemin greater than substance K greater than
neuromedin K; thus, the chief cell has a substance P-preferring tachykinin
binding site. Bombesin, cholecystokinin, and somatostatin had no effect on
substance P binding. Substance P stimulated pepsinogen secretion from
isolated canine oxyntic glands in dose-dependent fashion with a
half-maximal response occurring at a substance P dose of about 1
mM.(ABSTRACT TRUNCATED AT 250 WORDS)