Characterization of muscarinic cholinergic receptors on rat pancreatic acini by N-[3H]methylscopolamine binding. Their relationship with calcium 45 efflux and amylase secretion.

When dispersed acini from guinea pig pancreas are first incubated with carbachol, the subsequent binding of 125I-vasoactive intestinal peptide (VIP) is inhibited during a second incubation. This inhibitory action of carbachol on binding of 125I-VIP depends on time, temperature, and the concentration of carbachol in the first incubation and can be blocked by atropine. First incubating acini with A23187, ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA), cholecystokinin octapeptide, bombesin, or 12-O-tetradecanoylphorbol-13-acetate does not alter binding of 125I-VIP. Adding EGTA to the first incubation medium abolishes the effect of carbachol on binding of 125I-VIP. In control acini or acini first incubated with carbachol, approximately half of the bound 125I-VIP can be stripped by acetic acid. 125I-VIP interacts with two distinct classes of receptors on pancreatic acini. One has a high affinity for VIP (Kd, 1 nM); the other has a low affinity for VIP (Kd, 2 microM). First incubating acini with carbachol decreases the number but not the affinity of high-affinity VIP receptors with no change in the number or affinity of low-affinity VIP receptors. Pancreatic acini possess two classes of muscarinic cholinergic receptors: one has a high affinity (Kd, 4 microM) and the other has a low affinity (Kd, 698 microM) for carbachol. The dose-response curve for carbachol-induced inhibition of binding of 125I-VIP and that for occupation of low-affinity muscarinic cholinergic receptors by carbachol are similar.(ABSTRACT TRUNCATED AT 250 WORDS)

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Pharmacological Characterization of Muscarinic Cholinergic Receptors in Cat Pons and Cortex

Pharmacology ◽

10.1159/000139165 ◽

1994 ◽

Vol 48 (2) ◽

pp. 77-85 ◽

Cited By ~ 4

Author(s):

Helen A. Baghdoyan ◽

Berit X. Carlson ◽

Maria T. Roth

Keyword(s):

Cholinergic Receptors ◽

Pharmacological Characterization ◽

Muscarinic Cholinergic Receptors ◽

Muscarinic Cholinergic

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Bovine pancreatic polypeptide as an antagonist of muscarinic cholinergic receptors

AJP Gastrointestinal and Liver Physiology ◽

10.1152/ajpgi.1987.252.3.g384 ◽

1987 ◽

Vol 252 (3) ◽

pp. G384-G391

Author(s):

G. Z. Pan ◽

L. Lu ◽

J. M. Qian ◽

B. G. Xue

Keyword(s):

Pancreatic Polypeptide ◽

Pancreatic Enzyme ◽

Cholinergic Receptors ◽

Enzyme Secretion ◽

Amylase Secretion ◽

Enzyme Release ◽

Muscarinic Cholinergic Receptors ◽

Bovine Pancreatic Polypeptide ◽

Pancreatic Enzyme Secretion ◽

Muscarinic Cholinergic

In dispersed acini from rat pancreas, it was found that bovine pancreatic polypeptide (BPP) and its C-fragment hexapeptide amide (PP-6), at concentrations of 0.1 and 30 microM, respectively, could significantly inhibit amylase secretion stimulated by carbachol (P less than 0.01 or 0.05, respectively), and this inhibition by BPP was dose dependent. 45Ca outflux induced by carbachol was also inhibited by BPP or PP-6, but they had no effect on cholecystokinin octapeptide- (CCK-8) or A23187-stimulated 45Ca outflux. BPP was also capable of displacing the specific binding of [3H]quinuclidinyl benzilate to its receptors, and it possessed a higher affinity (ki 35 nM) than carbachol (Ki 1.8 microM) in binding with M-receptors. It is concluded from this study that BPP acts as an antagonist of muscarinic cholinergic receptors in rat pancreatic acini. In addition, BPP inhibited the potentiation of amylase secretion caused by the combination of carbachol plus secretin or vasoactive intestinal peptide. This may be a possible explanation of the inhibitory effect of BPP on secretin-induced pancreatic enzyme secretion shown in vivo, since pancreatic enzyme secretion stimulated by secretin under experimental conditions may be the result of potentiation of enzyme release produced by the peptide in combination with a cholinergic stimulant.

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Isolated parietal cells: [3H]QNB binding to putative cholinergic receptors

AJP Gastrointestinal and Liver Physiology ◽

10.1152/ajpgi.1980.239.3.g204 ◽

1980 ◽

Vol 239 (3) ◽

pp. G204-G209

Author(s):

R. Ecknauer ◽

W. J. Thompson ◽

L. R. Johnson ◽

G. C. Rosenfeld

Keyword(s):

Specific Binding ◽

Cholinergic Receptors ◽

Parietal Cells ◽

Cholinergic Antagonists ◽

Single Population ◽

Muscarinic Cholinergic Receptors ◽

Cholinergic Antagonist ◽

Muscarinic Cholinergic ◽

Quinuclidinyl Benzilate

The tritiated muscarinic cholinergic antagonist quinuclidinyl benzilate, [3H]QNB, was used as a direct probe for the detection and characterization of muscarinic cholinergic receptors associated with the particulate fraction of isolated and purified rat gastric muscosal parietal cells. Specific binding is saturable (Bmax = 55 fmol/mg protein, KD = 0.78 nM), shows a single population of binding sites, and has appropriate pharmacological specificity. Nanomolar concentrations of muscarinic cholinergic antagonists, such as atropine and scopolamine, inhibit [3H]QNB binding by 50%, whereas micromolar concentrations are needed for agonists, such as acetylcholine, oxotremorine, and carbamylcholine. Binding is also stereoselective as shown by the more than 1,000-fold difference in inhibitory potencies of the stereoisomers of benzetimide. Noncholinergic agents, including pentagastrin, histamine, and the H2-receptor antagonists cimetidine and metiamide, have little or no effect on [3H]QNB binding at concentrations of 100 microM. These data support the existence of specific parietal cell muscarinic cholinergic receptors with which the secretagogue acetylcholine may directly interact to initiate gastric acid secretion.

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