Autoradiographic identification of a gastrin receptor on the human parietal cell.

Gastrin plays an important role in regulating gastric acid secretion and gastrointestinal mucosal growth but its cellular sites of action in man have not been determined. Using cryostat sections of gastric mucosal tissue we have identified (125I-gastrin binding followed by fixation-wet emulsion autoradiography) and characterized (125I-gastrin binding followed by counting) a gastrin receptor binding site in the human stomach. This site displayed binding characteristics similar to those observed in isolated cell systems: specifically, 125I-gastrin binding was rapid (t1/2 approximately 10 min at 37 degrees C), temperature-dependent (3.

A novel gastrin-binding protein in the human eosinophil.

A specific and saturable interaction between 125I-gastrin and eosinophils was discovered in autoradiographs of human gastric mucosal tissue and confirmed in isolated and enriched preparations of WBC's. Gastrin displaced 125I-gastrin from eosinophils in a dose-dependent manner with a D50 = 11 uM. Scatchard analysis of the saturation curve indicated a single binding site of low affinity (Kd = 4.

The effects of sulfhydryl-modifying reagents on cholecystokinin-receptor interactions in guinea pig gastric glands.

The effects of a number of different sulfhydryl agents on cholecystokinin (CCK)-binding sites in isolated fundic gastric glands and gastric mucosal membranes from guinea pigs were evaluated. [125I]CCK octapeptide binding was significantly reduced when gastric glands were pretreated with iodoacetamide (IA; 10 mM), p-chloromercuribenzoate (PCMB; 0.1 mM), or N-ethylmaleimide (NEM; 0.

Secretin internalization and adenosine 3',5'-monophosphate levels in pancreatic acinar cells.

The internalization of [125I]secretin in pancreatic acinar cells was evaluated by differentiation of surface-bound and internalized radioligand with an acidified glycine buffer. The amount of surface-bound radioligand was 2-fold higher at 37 C than at 4 C between 15 and 60 min; internalized radioactivity was more than 10-fold greater at 37 C than at 4 C during the same time period. The effects of chloroquine, dithiothreitol (DTT), carbonyl cyanide m-chlorophenyl-hydrazone (CCCP), and dansylcadaverine on the binding and internalization of secretin were then evaluated.

Molecular identification and characterization of the gastrin receptor in guinea pig gastric glands.

The binding characteristics of 125I-labeled Leu15-gastrin and the molecular identification of the gastrin receptor was investigated in dispersed guinea pig gastric glands. The binding of [125I]gastrin to gastric glands was temperature dependent, saturable, and specific. At 37 C, the binding was rapid, became maximal within 10 min, and declined after 30 min; at 24 C, binding reached a steady state between 30 and 60 min.

Internalization and cellular processing of cholecystokinin in rat pancreatic acinar cells.

To evaluate the internalization of cholecystokinin, monoiodinated imidoester of cholecystokinin octapeptide [125I-(IE)-CCK-8] was bound to dispersed pancreatic acinar cells, and surface-bound and internalized radioligand were differentiated by treating with an acidified glycine buffer. The amount of internalized radioligand was four- and sevenfold greater at 24 and 37 degrees C than at 4 degrees C between 5 and 60 min of association. Specific binding of radioligand to cell surface receptors was not significantly different at these temperatures.

Effect of continuous infusions of CCK-8 on food intake and body and pancreatic weights in rats.

The ability of cholecystokinin (CCK) to act as a long-term satiety factor was assessed by its continuous infusion into the jugular veins of rats. Animals receiving a low dose of cholecystokinin octapeptide (CCK-8) (0.6 microgram CCK-8.

Degradation and processing of cholecystokinin in guinea pig fundic gastric glands.

The degradation of 125I-CCK8 in guinea pig fundic gastric glands was time and temperature dependent. At both 24 and 37 degrees C, dithiothreitol (DTT) and chloroquine reduced the degradation of the internalized 125I-CCK8. After 60 min of binding, DTT, chloroquine and DTT plus chloroquine together significantly reduced radioligand degradation by 43, 55 and 66%, respectively, compared to control at 24 degrees C, and these differences remained significant after 1, 2 and 3 hr of processing.

Receptor-mediated internalization and secretion of cholecystokinin into rat pancreatic duct fluid.

We measured cholecystokinin (CCK) in pancreatic duct secretions (PDS) after infusion of different amounts of CCK-8 (the C-terminal octapeptide of cholecystokinin) into rats. Injection of 23, 46, and 92 ng of CCK-8 increased immunoreactive cholecystokinin in PDS by 3-, 13-, and 28-fold above basal levels within 30 min. Continuous intravenous infusion of CCK-8 (50 ng/min) into rats for 30 min, followed by a 30-min rest period, and then a final infusion of peptide for another 30 min increased CCK in PDS only during the final period by 12-fold to 500 pg/30 min.

Effects of dietary fats and soybean protein on azaserine-induced pancreatic carcinogenesis and plasma cholecystokinin in the rat.

Both dietary unsaturated fat and raw soybean products are known to enhance pancreatic carcinogenesis when fed during the postinitiation phase. A comparison of these two dietary components was made to evaluate the relative potency of each ingredient for enhancing pancreatic carcinogenesis and to determine if this enhancement was correlated with an increase in plasma cholecystokinin (CCK) levels. Male Wistar rats were initiated with a single dose of azaserine (30 mg/kg body weight) at 14 days of age.

Role of cholecystokinin in intestinal phase of human pancreatic secretion.

In this study we have utilized a sensitive and specific radioimmunoassay for cholecystokinin (CCK) to determine the effects of a jejunal infusion (5 cc/min) of amino acids (44 g/liter), saline, and amino acids with intravenous atropine (20 micrograms X lg-1 X hr) on pancreatic exocrine secretion. Amino acids were found to stimulate pancreatic output of trypsin and release CCK, while a saline infusion at the same rate and osmolality (320 mosm/liter) failed to do so. In the presence of atropine, the amino acid infusion did not stimulate the pancreatic output of trypsin, despite an augmented CCK release.

A reduced pancreatic protein secretion in response to cholecystokinin (CCK) in the obese Zucker rat correlates with a reduced receptor capacity for CCK.

Pancreatic membrane receptors for cholecystokinin (CCK) in obese and nonobese Zucker rats were compared with the use of a biologically active [125I]iodo-CCK-8 radioprobe. Membrane homogenates from obese rats bound half the amount of radioligand in 2 h as did membranes from lean rats (specifically bound, 7.0% vs.

Role of cholecystokinin in the regulation of the interdigestive phase of pancreatic secretion.

The rate of pancreatic secretion during the interdigestive state varies with the phase of interdigestive motility. During phases II and III of interdigestive motility, pancreatic secretion is greatest, and minimal during phases I and IV. Pancreatic polypeptide and motilin have been reported to be increased during phases II and III but do not appear to be responsible for the stimulation of pancreatic secretion.

Cholecystokinin: a factor responsible for the enteral feedback control of pancreatic hypertrophyphy.

Chronic diversion of pancreatic and biliary secretions away from the proximal small intestine results in pancreatic hypertrophy in adult rats. Serum levels of cholecystokinin (CCK) were measured in age-matched control and surgically diverted rats at various times after operation by a radioimmunoassay method that was specific for the sulfated form of CCK. The concentration of CCK was markedly increased in bypassed rats as compared with controls.

The binding characteristics of 125I-gastrin and 125I-CCK8 to guinea pig fundic gastric glands differ: is there more than one binding site for peptides of the CCK-gastrin family?

The binding of biologically active 125I-labeled derivatives of the C-terminal octapeptide of cholecystokinin (125I-CCK8) and gastrin (125I-G) to dispersed guinea pig fundic glands were compared at 24 degrees C. Although both peptides share the same C-terminal pentapeptide sequence, differences were found in the amount of each radioligand bound to fundic glands, their dissociation behavior, and their Scatchard plots. However, each peptide was able to displace the other radioligand from the glands at nM concentrations which indicated that both peptides bound to the same site.

Immunoreactive cholecystokinin in human and rat plasma: correlation of pancreatic secretion in response to CCK.

Immunoreactive cholecystokinin (CCK) levels in human and rat plasma are described using a radioimmunoassay specific for the biologically active sulfated end of CCK. This assay detected significant changes in plasma cholecystokinin levels during intrajejunal administration of amino acids and intravenous infusions of CCK-8 which were followed by increased pancreatic secretion. In humans, the concentration (pg/ml) of plasma cholecystokinin increased from 10.

Effect of N-terminal iodination on the biological, immunological and receptor binding properties of secretion. A role for the alpha-amino group of histidine in stabilizing hormone-receptor interactions.

Both radiotrace labeled and high specific activity 125I-labeled derivatives of secretin were prepared by direction iodination of the histidyl residue with chloramine T [( 125I]secretin) and by conjugation of a preiodinated Bolton-Hunter group (iodo-3-(4-hydroxyphenyl)propionate) to the free alpha-amino group at the N-terminus [( 125I]BH-secretin). Following purification, the biological, immunological and receptor binding properties of both secretin derivatives were compared. [125I]secretin and [125I]BH-secretin were equally effective in a sensitive radioimmunoassay that detected secretin and secretin (5-27) but not CCK-8, VIP and glucagon.

Cholecystokinin receptor binding levels in the genetically obese rat brain.

Cholecystokinin (CCK) receptor binding levels were compared between groups of genetically obese (fa/fa) and non-obese (Fa/-) Zucker rats of both sexes. The radioligand used was the iodinated octapeptide (CCK-8). Binding was measured in eight brain regions.

Changes in cholecystokinin receptor binding in rat brain after food deprivation.

Levels of cholecystokinin (CCK) receptor binding in 7 brain regions were measured in two groups of adult male rats using iodinated CCK-8 as the radioligand. One group was deprived of food for 72 h prior to sacrifice and the other group had food available ad libitum. The deprivation resulted in a 13% decrease in body weight.

Characterization of cholecystokinin binding sites in rat cerebral cortex using a 125I-CCK-8 probe resistant to degradation.

Specific binding sites for cholecystokinin (CCK) have been characterized in a particulate membrane fraction of rat cerebral cortex using a biologically active 125I-labeled derivative of the C-terminal octapeptide of CCK (CCK-8) prepared by reaction with the iodinated form of the imidoester (125IIE), methyl-p-hydroxybenzimidate. The time course of binding to cortical membranes was rapid, temperature dependent, and saturable. Half-maximal binding at 24 degrees C was reached in 30 min and full binding at 120 min.

Identification and characterization of a specific receptor for cholecystokinin on isolated fundic glands from guinea pig gastric mucosa using a biologically active 125I-CCK-8 probe.

Specific binding sites for cholecystokinin (CCK) have been identified and characterized in fundic glands isolated by collagenase treatment from guinea pig gastric mucosa using a biologically active 125I-labeled derivative of the C-terminal octapeptide of CCK (125IIE-CCK-8). The time course of binding to these glands was rapid, temperature dependent and saturable. At 24, 30 and 37 degrees C, half-maximal binding was reached at 5 min and full binding at 30 min.

Preparation of an N-acetyl-octapeptide of cholecystokinin. The role of N-acetylation in protecting the octapeptide from degradation by smooth muscle tissues.

The C-terminal octapeptide of cholecystokinin (CCK-8) was acetylated on its lone N-terminal amino group using acetic anhydride in N,N-dimethylformamide. The acetylated derivative (Ac-CCK-8) and unreacted CCK-8 were separated from acetic anhydride and other reaction products by fractionation on Sephadex LH-20. Final purification was by thin-layer isoelectric focusing in a pH 2.