Regulation of bombesin receptors on pancreatic acini by cholecystokinin

1989 ◽  
Vol 256 (2) ◽  
pp. G291-G298
Author(s):  
M. Younes ◽  
S. A. Wank ◽  
R. Vinayek ◽  
R. T. Jensen ◽  
J. D. Gardner
Keyword(s):  
Guinea Pig ◽  
Response Curve ◽  
Binding Capacity ◽  
The Other ◽  
Single Class ◽  
Pancreatic Acini ◽  
Cck Receptors ◽  
Cyclic Monophosphate ◽  
High Affinity ◽  
Bombesin Receptors

When guinea pig pancreatic acini are first incubated with the COOH-terminal octapeptide of cholecystokinin (CCK-8), washed, and then reincubated with 125I-[Tyr4]bombesin (125I-[Tyr4]BN) there is a significant decrease in binding of 125I-[Tyr4]BN compared with that observed with pancreatic acini that have been first incubated with no additions. The CCK-8-induced decrease in binding is maximal after 90 min of first incubation is abolished by reducing the temperature of the first incubation from 37 to 4 degrees C or by adding L364,718 to the first incubation and cannot be reproduced by first incubating acini with A23187, 8-bromoadenosine 3',5'-cyclic monophosphate (8Br-cAMP), 8-bromoadenosine 3',5'-cyclic monophosphate (8Br-cGMP), or 12-O-tetradecanoylphorbol 13-acetate. 125I-[Tyr4]BN interacts with a single class of receptors on pancreatic acini, and first incubating acini with CCK-8 decreases the affinity of BN receptors for BN with no change in the maximal binding capacity. CCK-8 does not alter the rate at which bound 125I-[Tyr4]BN dissociates from pancreatic acini; therefore, CCK-8 must alter the rate at which the radiolabeled BN analogue associates with its receptor. Pancreatic acini possess two classes of CCK receptors: one has a high affinity for CCK-8; the other has a low affinity for CCK-8. The dose-response curve for CCK-8-induced inhibition of binding of 125I-[Tyr4]BN appears to to reflect occupation of low-affinity CCK receptors by CCK-8.(ABSTRACT TRUNCATED AT 250 WORDS)

Characterization of gastrin receptors on guinea pig pancreatic acini

1987 ◽  
Vol 253 (6) ◽  
pp. G793-G801 ◽  
Author(s):  
D. H. Yu ◽  
M. Noguchi ◽  
Z. C. Zhou ◽  
M. L. Villanueva ◽  
J. D. Gardner ◽  
...  
Keyword(s):  
Guinea Pig ◽  
Binding Capacity ◽  
Pancreatic Tumors ◽  
Amylase Secretion ◽  
Single Class ◽  
Amylase Release ◽  
Pancreatic Acini ◽  
Cyclic Monophosphate ◽  
Relative Potencies

Recent studies have demonstrated gastrin receptors in some pancreatic tumors and that gastrin is a potent stimulant of pancreatic Na+-H+ exchange. In the present study we used 125I-labeled gastrin (125I-gastrin) to characterize gastrin receptors on guinea pig pancreatic acini. Binding of 125I-gastrin was temperature dependent, saturable, and specific for gastrin-related peptides. Analysis demonstrated a single class of receptors with high affinity for gastrin (Kd = 1.5 nM) and a binding capacity of 1 fmol/mg protein. Binding of 125I-gastrin was inhibited with the following relative potencies (Kd): cholecystokinin octapeptide (CCK-8) (0.35 nM) greater than gastrin-17-I = gastrin-34-I (1.5 nM) greater than pentagastrin (7 nM) greater than desulfated [des(SO3)]CCK-8 (28 nM) greater than CCK-4 (508 nM) and by the receptor antagonists CBZ-CCK-27-32-NH2 (3.5 microM) greater than proglumide analogue 10 (30 microM) greater than asperlicin (265 microM) greater than Bt2-guanosine 3',5'-cyclic monophosphate (828 micron). In contrast, for both stimulation of enzyme secretion and inhibition of binding of 125I-CCK-8 the relative potencies were CCK-8 much greater than des(SO3)CCK-8 greater than gastrin-17-I = gastrin-34-I greater than pentagastrin greater than CCK-4. For each receptor antagonist the dose-inhibition curve for gastrin-stimulated amylase release was superimpossible with that for CCK-8-stimulated amylase release. Gastrin-17-I at concentrations less than 0.1 microM did not potentiate carbachol or vasoactive intestinal peptide-stimulated amylase secretion and did not affect basal or stimulated adenosine 3',5'-cyclic monophosphate or 45Ca outflux.(ABSTRACT TRUNCATED AT 250 WORDS)

Carbachol desensitizes pancreatic enzyme secretion by downregulation of receptors

1990 ◽  
Vol 258 (1) ◽  
pp. G107-G121 ◽  
Author(s):  
R. Vinayek ◽  
M. Murakami ◽  
C. M. Sharp ◽  
R. T. Jensen ◽  
J. D. Gardner
Keyword(s):  
Pancreatic Enzyme ◽  
Cholinergic Receptors ◽  
Single Class ◽  
Amylase Release ◽  
Pancreatic Acini ◽  
Cck Receptors ◽  
High Affinity ◽  
Kinase C ◽  
Pancreatic Enzyme Secretion ◽  
Bombesin Receptors

First incubating guinea pig pancreatic acini with carbachol reduced the subsequent stimulation of amylase release caused by carbachol, cholecystokinin octapeptide (CCK-8), and bombesin but not that caused by vasoactive intestinal peptide, substance P, 8-bromoadenosine 3',5'-cyclic monophosphate, A23187, or 12-O-tetradecanoylphorbol-13-acetate. Carbachol also reduced the subsequent binding of N-[3H]methylscopolamine, 125I-CCK-8, and 125I-[Tyr4]bombesin. Pancreatic acini possess a high-affinity class of cholinergic receptors and a low-affinity cholinergic receptors appears to produce the reduction in carbachol-stimulated amylase release and binding of N-[3H]methylscopolamine. First incubating acini with carbachol caused a complete loss of high-affinity cholinergic receptors with no change in the number or affinity of low-affinity cholinergic receptors. Carbachol occupation of low-affinity cholinergic receptors appears to produce the reduction in CCK-8- and bombesin-stimulated amylase release and in binding of 125I-CCK-8 and 125I-[Tyr4]bombesin. Acini possess two classes of CCK receptors. One class has a high affinity for CCK-8; the other class has a low affinity for CCK-8. First incubating acini with carbachol caused a 60% decrease in the number of high-affinity CCK receptors with no change in the number of low-affinity receptors or the affinities of either class of receptors for CCK-8. Acini possess a single class of bombesin receptors, and first incubating acini with carbachol caused a 40% decrease in the number of bombesin receptors with no change in their affinity for bombesin. 12-O-tetradecanoyl phorbol-13-acetate reproduced the action of carbachol on binding of N-[3H]methylscopolamine and 125I-CCK-8 but not on binding of 125I-[Tyr4]bombesin, suggesting that carbachol activation of protein kinase C may in some way mediate the effect of carbachol on receptors for carbachol and those for CCK but not that on receptors for bombesin.

Carbachol-induced down-regulation of high-affinity receptors for vasoactive intestinal peptide

1989 ◽  
Vol 257 (3) ◽  
pp. G402-G408
Author(s):  
M. Murakami ◽  
R. Vinayek ◽  
R. T. Jensen ◽  
J. D. Gardner
Keyword(s):  
Vasoactive Intestinal Peptide ◽  
Response Curve ◽  
Cholinergic Receptors ◽  
The Other ◽  
Tetraacetic Acid ◽  
Muscarinic Cholinergic Receptors ◽  
Pancreatic Acini ◽  
Vip Receptors ◽  
High Affinity ◽  
Muscarinic Cholinergic

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)

Carbachol acts through protein kinase C to modulate cholecystokinin receptors on pancreatic acini

1991 ◽  
Vol 261 (6) ◽  
pp. G981-G986 ◽  
Author(s):  
D. S. Louie ◽  
O. Y. Chung
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Binding Capacity ◽  
Muscarinic Agonist ◽  
Amylase Release ◽  
Pancreatic Acini ◽  
Cck Receptors ◽  
High Affinity ◽  
Total Binding ◽  
Kinase C

Cholecystokinin (CCK) and cholinergic agonists are both major stimulants of pancreatic enzyme secretion and both utilize a common calcium-phosphoinositide-mediated receptor coupling system. In this study we investigated the modulation of pancreatic acinar CCK receptors by the muscarinic agonist carbachol (CCh) and investigated the intracellular mechanisms involved in the modulation. Acini were isolated from rat pancreas and dispersed in N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid-Ringer solution. Preincubation with 0.1 mM carbachol for 60 min reduced the CCK octapeptide (CCK-8; 100 pM)-stimulated amylase release by 43 +/- 5%. Binding of 125I-Bolton-Hunter-labeled CCK-8 (125I-BH-CCK-8) revealed two classes of CCK receptors, a high affinity with a dissociation constant (Kd) of 20 pM and a low affinity with a Kd of 2.3 nM. Pretreatment with 100 microM CCh decreased total binding by 35 +/- 6%, affecting the binding capacity of the high-affinity site, without change in the maximal binding capacity of the low-affinity site and no change in the Kd of either site. Preincubation of acini with 12-O-tetradecanoylphorbol 12,13-acetate (TPA, 1 microM), an activator of protein kinase C (PKC), decreased subsequent CCK-8-stimulated amylase release, and total binding of 125I-BH-CCK-8 to a similar extent as with pretreatment with CCh. The inhibitory effect of TPA or CCh on CCK-8-stimulated amylase release was reversed by simultaneous preincubation with H-7, an inhibitor of PKC. Pretreatment of acini with the calcium ionophore A23187, vasoactive intestinal peptide, or 8-bromoadenosine 3',5'-cyclic monophosphate had no effect on 125I-BH-CCK-8 binding. After CCh or TPA preincubation, CCK-8-stimulated production of [3H]inositol phosphates was inhibited by at least 49%.(ABSTRACT TRUNCATED AT 250 WORDS)

Receptor occupation, calcium mobilization, and amylase release in pancreatic acini: effect of CCK-JMV-180

1989 ◽  
Vol 257 (2) ◽  
pp. G202-G209 ◽  
Author(s):  
S. Sato ◽  
H. A. Stark ◽  
J. Martinez ◽  
M. A. Beaven ◽  
R. T. Jensen ◽  
...  
Keyword(s):  
Response Curve ◽  
Cytosolic Calcium ◽  
Calcium Mobilization ◽  
Amylase Release ◽  
Pancreatic Acini ◽  
Rat Pancreas ◽  
Cck Receptors ◽  
High Affinity ◽  
Low Concentrations ◽  
The Relationship

We examined the relationships between receptor occupation, calcium mobilization, and stimulated amylase release for cholecystokinin octapeptide (CCK-8) and for CCK-JMV-180, an analogue of the COOH-terminal heptapeptide of CCK having the structure Boc-Tyr(SO3)-Nle-Gly-Trp-Nle-Asp-2-phenylethyl ester using dispersed acini from rat pancreas. CCK-8 and CCK-JMV-180 each bind to two classes of CCK receptors: one class has a high affinity for CCK-8 and CCK-JMV-180 and the other class has a low affinity for CCK-8 and CCK-JMV-180. Mobilization of cellular calcium was assessed by measuring cytosolic calcium with a fluorescent indicator and by measuring outflux of radioactive calcium from preloaded cells. In terms of causing an increase in cytosolic calcium or an increase in calcium outflux, CCK-JMV-180 was 50-60% as efficacious as CCK-8. Analysis of the relationship between receptor occupation and calcium mobilization caused by CCK-8 and CCK-JMV-180 in combination indicates that calcium mobilization is caused by occupation of low-affinity CCK receptors. Comparison of the dose-response curve for calcium mobilization and amylase release stimulated by CCK-8 or CCK-JMV-180 indicates that very low concentrations of each peptide stimulate amylase release without causing detectable calcium mobilization. At these very low concentrations, CCK-8 or CCK-JMV-180 do not cause potentiation of amylase release when combined with vasoactive intestinal peptide.

Cholecystokinin downregulates receptors for vasoactive intestinal peptide and secretin in rat pancreatic acini

1990 ◽  
Vol 258 (3) ◽  
pp. G395-G403
Author(s):  
S. Katsushima ◽  
H. Adachi ◽  
T. Honda ◽  
S. Sato ◽  
T. Kusui ◽  
...  
Keyword(s):  
Vasoactive Intestinal Peptide ◽  
Binding Sites ◽  
Specific Binding ◽  
Amylase Secretion ◽  
Affinity Binding ◽  
Pancreatic Acini ◽  
Cck Receptors ◽  
Cyclic Monophosphate ◽  
Apparent Decrease ◽  
Specific Antagonist

We examined the effect of cholecystokinin (CCK) on the receptors for vasoactive intestinal peptide (VIP) and secretin in rat pancreatic acini. CCK decreased the specific binding of 125I-VIP and 125I-secretin by 42 and 51%, respectively. This CCK-induced inhibition was caused by an apparent decrease in the capacity of high-affinity binding sites of VIP and secretin receptors. CR 1409, a specific antagonist of CCK, abolished CCK-induced binding inhibition, whereas 12-O-tetradecanoylphorbol-13-acetate, A23187, and cycloheximide did not affect the binding of the radioligands. Both N2,O2-dibutyryl guanosine 3',5'-cyclic monophosphate (Bt2cGMP) and nitroprusside inhibited the specific binding of 125I-VIP. This inhibition, however, was because of an apparent decrease in the capacity of low-affinity binding sites on VIP receptors. CCK-induced downregulation of VIP and secretin receptors was associated with the diminished acinar response to VIP or secretin-induced adenosine 3',5'-cyclic monophosphate accumulation and amylase secretion, whereas neither Bt2cGMP nor nitroprusside affected VIP-induced amylase secretion. Data suggest that CCK-induced downregulation is mediated by the initial interaction of CCK with CCK receptors followed by some postreceptor process, which appears unrelated to protein kinase C, calcium mobilization, decrease in protein synthesis, or cellular cGMP increases. This downregulation, at least in part, accounts for CCK-induced restricted stimulation of amylase secretion by VIP and secretin.

Maturation of cholecystokinin receptors in pancreatic acini of rats

1986 ◽  
Vol 250 (5) ◽  
pp. G594-G597 ◽  
Author(s):  
Y. K. Leung ◽  
P. C. Lee ◽  
E. Lebenthal
Keyword(s):  
Receptor Binding ◽  
Binding Capacity ◽  
Amylase Secretion ◽  
Newborn Rat ◽  
Pancreatic Acini ◽  
Binding System ◽  
High Affinity ◽  
Cholecystokinin Receptors ◽  
Maximal Binding

Amylase secretion by fetal and newborn rat pancreata was shown not to respond to cholecystokinin (CCK) stimulation. Binding of 125I-Bolton-Hunter (125I-BH)-CCK-8 to dispersed pancreatic acini from rats at various perinatal ages was measured and compared with adults. Binding occurred maximally at 30 min at 37 degrees C at all ages. Maximal binding increased with age. The capacity and affinity of the CCK-receptor binding system was analyzed by Scatchard's method. The results revealed that the capacity of the high-affinity component gradually increases with age, whereas that of the low-affinity component remains relatively constant. Amylase secretion due to CCK stimulation also increases with age, suggesting that the lack of responsiveness of pancreata of pups to secretagogue is due to a low binding capacity of the high-affinity component of the receptors.

scholarly journals Identification of serum GH-binding proteins in the goldfish (Carassius auratus) and comparison with mammalian GH-binding proteins

1999 ◽  
Vol 161 (2) ◽  
pp. 255-262 ◽  
Author(s):  
Y Zhang ◽  
TA Marchant
Keyword(s):  
Binding Sites ◽  
Carassius Auratus ◽  
Binding Proteins ◽  
Binding Capacity ◽  
Sea Bream ◽  
Single Class ◽  
Binding Characteristics ◽  
High Affinity ◽  
Goldfish Carassius Auratus ◽  
Reducing Conditions

The present study constitutes the characterization of a specific, high-affinity GH-binding protein (GHBP) in the serum of a teleost, the goldfish (Carassius auratus). GH-binding assay and ligand blotting techniques were employed to identify GHBPs in goldfish serum and hepatocyte culture medium. The binding characteristics and apparent molecular weights (Mr) of goldfish GHBPs were also compared with those of rabbit and rat. LIGAND analysis identified a single class of high-affinity and low-capacity binding sites for iodinated recombinant carp GH (rcGH) in the goldfish serum, with an association constant (Ka) of 20.1x10(9) M-1 and a maximum binding capacity (Bmax) of 161 fmol ml-1 serum. A single class of binding sites for iodinated recombinant sea bream GH and bovine GH (bGH) was also found in goldfish serum, but with a much lower affinity than that of rcGH. The binding affinity for iodinated bGH in rabbit and rat sera was found to be similar to that reported previously. Ligand blotting revealed multiple forms of GHBPs in sera of goldfish, rabbit and rat with Mr ranging from 70 kDa to 400 kDa and 27 kDa to 240 kDa under non-reducing and reducing conditions respectively. A prominent band with Mr of 66 kDa and a minor band with Mr of 27 kDa were observed to occur in sera from all three species under reducing conditions. Iodoacetamide promoted the shedding of three GHBPs with Mr of 25, 40 and 45 kDa from the cultured goldfish hepatocytes. The appearance of all bands was completely inhibited by the presence of excess unlabeled rcGH. Our results provide clear evidence that a GHBP exists in the goldfish and indicate that more information on teleost GHBPs is needed if the physiology of growth in teleosts is to be fully understood.

Uptake of 3,5,3′-l-tri-iodothyronine in human erythrocytes

1989 ◽  
Vol 121 (3) ◽  
pp. 585-591 ◽  
Author(s):  
K. Yamauchi ◽  
R. Horiuchi ◽  
H. Takikawa
Keyword(s):  
Binding Sites ◽  
Binding Capacity ◽  
Human Erythrocytes ◽  
The Other ◽  
Transport Pathway ◽  
High Affinity ◽  
High Affinity Site ◽  
Maximum Binding Capacity ◽  
Energy Dependent ◽  
Dependent Pathway

ABSTRACT The mechanisms of 3,5,3′-l-tri-iodothyronine (T3) uptake into human erythrocytes were examined. Purified membranes of human erythrocytes were shown to have two classes of T3-binding sites with one being a high-affinity site (dissociation constant, 59·2±17·8 nmol/l; maximum binding capacity, 344·3 ± 95·5 fmol/μg protein). Furthermore, it was shown that there were two pathways for T3 uptake in human erythrocytes; one was saturable, stereospecific (T3»thyroxine > 3,5,3′-d-tri-iodothyronine), energydependent and dominant at 15 °C; the other was not displaced by unlabelled T3 and was energyindependent but did not occur by passive diffusion. The former pathway which, it is suggested, is a receptor-mediated transport pathway, was inhibited by monodansylcadaverine, phloretin or oligomycin at 15 or 37 °C, but the latter pathway was not inhibited by these inhibitors. Our results strongly suggest that uptake of T3 by the energy-independent pathway became predominant over the energy-dependent pathway at 37 °C and accounted for 83% of total T3 uptake of human erythrocytes. Journal of Endocrinology (1989) 121, 585–591

Hydrocortisone treatment increases the sensitivity and responsiveness to cholecystokinin in rat pancreas

1989 ◽  
Vol 257 (3) ◽  
pp. G364-G370 ◽  
Author(s):  
M. Otsuki ◽  
Y. Okabayashi ◽  
T. Nakamura ◽  
M. Fujii ◽  
S. Tani ◽  
...  
Keyword(s):  
Ionophore A23187 ◽  
Pancreatic Acini ◽  
Cck Receptors ◽  
Cyclic Monophosphate ◽  
Dna Contents ◽  
Wet Weight ◽  
Dose Dependent Increase ◽  
Dose Dependent ◽  
Hydrocortisone Treatment

The effects of hydrocortisone treatment on the secretory abilities of pancreatic acini to various secretagogues were studied. Rats were given subcutaneous injections of hydrocortisone at doses of 1.25, 2.5, or 5.0 mg/kg body wt once daily for 7 days. Hydrocortisone led to a small dose-dependent increase in pancreatic wet weight per 100 g body wt, which was associated with an increase in both total protein and DNA contents. In acini prepared from hydrocortisone-treated rats, both the responsiveness and the sensitivity to cholecystokinin octapeptide (CCK-8) was increased. The concentration dependence of cellular Ca2+ mobilization in response to CCK-8 was also shifted to lower concentrations in acini from hydrocortisone-treated rats compared with control rat acini. In vivo administration of hydrocortisone caused a significant increase in the affinity of 125I-CCK-8 binding to high-affinity receptors. The secretory responsiveness to carbamylcholine and bombesin, but not to secretin, was also increased but without any change in the sensitivity. Moreover, the hydrocortisone treatment increased the secretory responsiveness of acini to the Ca2+ ionophore A23187 and the phorbol ester 12-O-tetradecanoylphorbol-13-acetate but did not to an adenosine 3',5'-cyclic monophosphate analogue, 8-bromoadenosine 3',5'-cyclic monophosphate. The present observations suggest that in vivo glucocorticoid administration affects both the CCK receptors and a postreceptor loci.

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