AJP - Gastrointestinal and Liver Physiology, Vol 246, Issue 5 550-G555, Copyright © 1984 by American Physiological Society
Ontogeny of gastric mucosal muscarinic receptor and sensitivity to carbachol
E. R. Seidel and L. R. Johnson
Development of the muscarinic cholinergic receptor and sensitivity of
oxyntic gland mucosa to a muscarinic agonist were studied in rats of
various ages. The gastric lumen of the fetal rat at the 20th day of
gestation contained a statistically significant amount of basal pepsin,
which increased log linearly over the first 30 days of life. Carbachol was
effective in stimulating the secretion of pepsin as early as 12 h after
birth. Basal acid could be measured in the gastric lumen 12 h after birth.
The secretion of basal acid increased log linearly over the first 30 days
of life. Carbachol was an effective secretagogue even in the fetal rat. The
density of the muscarinic cholinergic receptor of the adult rat oxyntic
gland mucosa was 99.3 fmol/mg protein with an apparent equilibrium
dissociation constant for quinuclidinyl benzilate of 0.40 nM. The receptor
was well developed even in the fetal rat, which bound 79.6 fmol/mg protein
with an apparent equilibrium dissociation constant of 0.26 nM. Except for
immediately after birth, receptor density was maintained between 70 and 90%
of the adult level over the first 30 days of life. These results suggest
that cholinergic regulation of gastric acid and pepsin secretion is
probably functional by either late gestation or at least immediately after
birth.
