vasoactive-intestinal-peptide and gastrin-17

An immunological role for eosinophils has been well established. However, roles for eosinophils in the physiological functions of the organs they populate are little explored.. Fixed, frozen, then vibratomed sections of rat stomach were exposed to biotinylated 1-17 gastrin (bG17), biotinylated gastrin-releasing peptide (bGRP), biotinylated neuromedin C (bNC), biotinylated vasoactive intestinal peptide (bVIP), and biotinylated substance P (bSP). Binding sites were identified using an avidin-biotin-glucose oxidase complex and tetranitroblue tetrazolium staining.. bG17, bGRP, and bNC all bound to cells in the lamina propria and to a lesser extent in the submucosa. Neither bVIP nor bSP bound to cells in these sections. Stained cells were identified as eosinophils in the light microscope on the basis of their distribution and staining properties using the Luna stain for eosinophils and in the transmission electron microscope (TEM) on the basis of a light/TEM matching process. Plastic sections viewed in the light microscope showed that stain was localized to a granular component in the cytoplasm of the eosinophils. No other cell type, specifically neither mast cells nor plasma cells, stained. G17 competed for the bG17 binding site better than did NC. A competition study in which polyglutamic acid failed to compete with bG17 for the binding site, and the observation that bG17, bGRP, and bNC did not bind to other positively charged sites (e.g., collagen, red blood corpuscles), demonstrated that binding was not due to nonspecific electrostatic interactions alone. Binding of bG17 to a CCK(B)/gastrin-type receptor was ruled out when specific receptor antagonists failed to block binding.. The particulate nature of the binding site suggests a secretory substance. If so, eosinophils might use that substance to destroy, neutralize, or control the activity of peptide hormones bound to it in the extracellular space.

Topics: Animals; Binding, Competitive; Biotinylation; Bombesin; Coloring Agents; Cytoplasmic Granules; Eosinophils; Frozen Sections; Gastric Mucosa; Gastrins; Microscopy, Electron; Neuropeptides; Peptide Fragments; Rats; Rats, Sprague-Dawley; Substance P; Tissue Fixation; Vasoactive Intestinal Peptide

Several studies examined in vivo and in vitro biologic activity of the human gallbladder in response to cholecystokinin (CCK). However, few studies have demonstrated directly the interaction of CCK with receptors on the human gallbladder, which is responsible for this biologic activity.. To characterize CCK receptors on human gallbladder tissue, gallbladders were removed from human donor grafts that were being used for liver transplantation. The gallbladders were rapidly frozen and sectioned for measurement of binding of 125I-Bolton-Hunter-labeled-CCK-8 and were cut into strips for in vitro bioassay.. Binding of 125I-BH-CCK-8 to human gallbladder was saturable, specific, and dependent on time, pH, and temperature. The binding was inhibited only by cholecystokinin-related peptides including CCK-8 (IC50 10 +/- 1.0 nmol/L) (mean +/- SD), des(SO3) CCK-8 (IC50 0.9 +/- 0.2 mumol/L), and gastrin-17-I (IC50 9.0 +/- 2.0 mumol/L) or specific CCK receptor antagonist L-364,718. Computer analysis of binding of 125I-BH-CCK-8 to gallbladder tissue showed a single class of binding sites with high affinity for CCK-8. Autoradiography localized binding of 125I-BH-CCK-8 only to the smooth muscle layer of the gallbladder. In the bioassay des(SO3) CCK-8 (EC50 1.2 +/- 0.7 mumol/L) and gastrin-17-I (EC50 4.5 +/- 2.4 mumol/L) were 150- and 563-fold less potent than CCK-8 (EC50 8.0 +/- 2.2 nmol/L). The relative potencies of CCK agonists for inhibiting binding of 125I-BH-CCK-8 agreed closely with their relative potencies for causing gallbladder contraction. The dose-response curve for CCK-8 alone to induce gallbladder contraction was not significantly different from those caused by CCK-8 plus 1 mumol/L tetrodotoxin or 1 mumol/L atropine.. These results characterized the CCK receptors on smooth muscle of human gallbladder as sulfate dependent and causing gallbladder contraction.

Topics: Autoradiography; Benzodiazepinones; Binding Sites; Carbachol; Devazepide; Dose-Response Relationship, Drug; Gallbladder; Gastrins; Hormones; Humans; Hydrogen-Ion Concentration; In Vitro Techniques; Iodine Radioisotopes; Muscle Contraction; Muscle, Smooth; Receptors, Cholecystokinin; Reference Values; Secretin; Serotonin; Sincalide; Substance P; Temperature; Vasoactive Intestinal Peptide

Twenty-four male albino rats were given daily intraperitoneal injections of vasoactive intestinal polypeptide (VIP), motilin, human gastrin I (1-17) or the diluent control vehicle at a dose of 100 micrograms/kg for four consecutive days and food intake, water intake, body weight, and running wheel activity were determined every 24 hours. Animals injected with motilin or human gastrin I (1-17) exhibited decreased food intake relative to those injected with VIP or diluent, which did not differ from each other, although food intake increased reliably over days. The mean water consumption followed the same pattern as that of food intake. As expected from the above results, VIP produced weight gains as compared with rats injected with motilin or gastrin but not reliably more than after diluent. A reliable effect of trials for weight gain was the greatest on day three. Running wheel activity was not affected by injections of human gastrin I (1-17), motilin, or diluent but was reliably decreased by VIP. No significant differences existed across days. Although the results indicate that GI peptides may affect behavior when injected systemically and that like other peptides they have multiple effects, caution is urged in the interpretation of behavioral results at this time.

Topics: Animals; Behavior, Animal; Body Weight; Drinking; Eating; Gastrins; Gastrointestinal Hormones; Male; Motilin; Motor Activity; Rats; Rats, Inbred Strains; Vasoactive Intestinal Peptide