Functional differences of Na+/Ca2+ exchanger expression in Ca2+ transport system of smooth muscle of guinea pig stomach

The plasma membrane ATP-dependent Ca2+ pump and the Na+/Ca2+ exchanger (NCX) are the major means of Ca2+ extrusion in smooth muscle. However, little is known regarding distribution and function of the NCX in guinea pig gastric smooth muscle. The expression pattern and distribution of NCX isoforms suggest a role as a regulator of Ca2+ transport in cells. Na+ pump inhibition and the consequent to removal of K+ caused gradual contraction in fundus. In contrast, the response was significantly less in antrum. Western blotting analysis revealed that NCX1 and NCX2 are the predominant NCX isoforms expressed in stomach, the former was expressed strongly in antrum, whereas the latter displayed greater expression in fundus. Isolated plasma membrane fractions derived from gastric fundus smooth muscle were also investigated to clarify the relationship between NCX protein expression and function. Na+-dependent Ca2+ uptake increased directly with Ca2+ concentration. Ca2+ uptake in Na+-loaded vesicles was markedly elevated in comparison with K+-loaded vesicles. Additionally, Ca2+ uptake by the Na+- or K+-loaded vesicles was substantially higher in the presence of A23187 than in its absence. The result can be explained based on the assumption that Na+ gradients facilitate downhill movement of Ca2+. Na+-dependent Ca2+ uptake was abolished by the monovalent cationic ionophore, monensin. NaCl enhanced Ca2+ efflux from vesicles, and this efflux was significantly inhibited by gramicidin. Results documented evidence that NCX2 isoform functionally contributes to Ca2+ extrusion and maintenance of contraction-relaxation cycle in gastric fundus smooth muscle.Key words: stomach, smooth muscle, Na+/Ca2+ exchanger (NCX), NCX2.

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Smooth muscle cells from guinea pig stomach possess high-affinity galanin receptors that mediate relaxation

AJP Gastrointestinal and Liver Physiology ◽

10.1152/ajpgi.1994.266.5.g839 ◽

1994 ◽

Vol 266 (5) ◽

pp. G839-G845 ◽

Cited By ~ 1

Author(s):

Z. F. Gu ◽

T. K. Pradhan ◽

D. H. Coy ◽

R. T. Jensen

Keyword(s):

Smooth Muscle ◽

Guinea Pig ◽

Smooth Muscle Cells ◽

Muscle Cells ◽

Maximal Effect ◽

Dependent Manner ◽

High Affinity ◽

Gastric Smooth Muscle ◽

Guinea Pig Stomach ◽

Galanin Receptors

Galanin-like immunoactivity occurs in nerves and plexi in muscle layers throughout gastrointestinal tract including the stomach. Galanin can affect gastric emptying and contraction or relaxation of gastric muscle in different species. The aim of this study was to investigate the direct effect of galanin on dispersed gastric smooth muscle cells and to characterize any galanin receptors that mediated any effect. Dispersed gastric smooth muscle cells were prepared from guinea pig stomach by collagenase digestion. Porcine galanin (p-galanin; 1 microM) did not stimulate contraction when present alone; however, p-galanin (1 microM) inhibited carbachol-induced contraction with a half-maximal effect at 7 nM. p-Galanin (1 microM) increased cellular adenosine 3',5'-cyclic monophosphate (cAMP) content by 10 s and caused a maximal increase of 80% over basal. 125I-galanin (porcine) bound to dispersed cells in a time- and temperature-dependent manner. Binding was saturable, reversible, and specific. Binding of 125I-galanin was inhibited almost equally by porcine and rat galanin (Ki = 6-8 nM) but was not inhibited by the galanin-associated peptide [preprogalanin-(108-123)]. The fragment galanin-(1-16) was equally potent to rat galanin; however, the fragment galanin-(9-29) was 56-fold less potent (Ki = 370 nM). Computer analysis demonstrated there were two binding sites for p-galanin on gastric smooth muscle cells, a high-affinity site (Kd = 2.6 nM) with low capacity (Bmax = 175 fmol/mg protein) and a low-affinity site (Kd = 150 nM) with large capacity (Bmax = 3,611 fmol/mg protein).(ABSTRACT TRUNCATED AT 250 WORDS)

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Su1539 Mechanisms of PTHrP-induced Suppression of Gastric Smooth Muscle Contractility in the Guinea Pig Stomach

Gastroenterology ◽

10.1016/s0016-5085(16)31792-9 ◽

2016 ◽

Vol 150 (4) ◽

pp. S521

Author(s):

Hideomi Ohguchi ◽

Hikaru Hashitani ◽

Kenro Imaeda ◽

Mayo Hachiya ◽

Eiji Kubota ◽

...

Keyword(s):

Smooth Muscle ◽

Guinea Pig ◽

Muscle Contractility ◽

Smooth Muscle Contractility ◽

Gastric Smooth Muscle ◽

Guinea Pig Stomach

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Inhibition of peptidases potentiates enkephalin-stimulated contraction of gastric muscle cells

AJP Gastrointestinal and Liver Physiology ◽

10.1152/ajpgi.1991.261.3.g476 ◽

1991 ◽

Vol 261 (3) ◽

pp. G476-G484 ◽

Cited By ~ 1

Author(s):

D. Menozzi ◽

Z. F. Gu ◽

P. N. Maton ◽

N. W. Bunnett

Keyword(s):

Smooth Muscle ◽

Cell Surface ◽

Guinea Pig ◽

Muscle Cells ◽

Peptidase Activity ◽

Maximal Contraction ◽

Physical Relationship ◽

Gastric Smooth Muscle ◽

Gastric Muscle ◽

Guinea Pig Stomach

Cell surface peptidases degrade enkephalins and thereby restrict the number of molecules available to activate receptors. The effects of peptidase inhibitors on degradation of enkephalins and on enkephalin-stimulated contraction of gastric smooth muscle cells were examined. Muscle cells dispersed from the guinea pig stomach degraded [Tyr1-3H] [Leu5]enkephalin (41.6 +/- 9.0% degradation at 60 min incubation, mean +/- SD, n = 4 animals). Amastatin (10 microM, an aminopeptidase inhibitor) inhibited degradation by 72.1 +/- 1.5% The residual peptidase activity was inhibited by phosphoramidon (1 microM, an endopeptidase EC 3.4.24.11 inhibitor) by 58.0 +/- 11.0%. [Tyr1-125I] [Met5]enkephalin was similarly degraded. Phosphoramidon (1 microM) inhibited the degradation of the aminopeptidase-resistant peptide [Tyr1-3H] [D-Ala2]-[Leu5]enkephalin by greater than 95%. [Met5]enkephalin, incubated with cells for 30 s, stimulated contraction [50% maximal contraction (EC50) 120 +/- 50 nM, n = 6]. Pretreatment of cells with phosphoramidon alone, amastatin alone, or phosphoramidon plus amastatin, caused 20-fold (EC50 6.5 +/- 1.1 nM), 2-fold (EC50 63 +/- 23 nM), and 100-fold (EC50 1.1 +/- 0.3 nM) increase in potency of [Met5]enkephalin, respectively. The results show that endopeptidase EC 3.4.24.11 and aminopeptidases contribute to degradation of enkephalins by gastric muscle cells. The rapidity and magnitude of the potentiating effects of the inhibitors on enkephalin-stimulated contraction suggest a close physical relationship between the peptidases and the enkephalin receptors.

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Identification of neurotransmitters by selective protection of postjunctional receptors

AJP Gastrointestinal and Liver Physiology ◽

10.1152/ajpgi.1990.258.1.g103 ◽

1990 ◽

Vol 258 (1) ◽

pp. G103-G106

Author(s):

J. R. Grider

Keyword(s):

Smooth Muscle ◽

Guinea Pig ◽

Gastric Fundus ◽

Membrane Receptors ◽

Field Stimulation ◽

Dibutyryl Camp ◽

Selective Protection ◽

Gastric Smooth Muscle ◽

Selective Ligands ◽

Before And After

The neurotransmitter responsible for relaxation of gastric smooth muscle was identified by a technique involving the use of selective ligands to protect postjunctional receptors combined with inactivation of all other receptors with N-ethylmaleimide (NEM). Relaxation in response to field stimulation (80 V, 1 ms, 0.5-8 Hz) and to maximally effective concentrations of vasoactive intestinal peptide (VIP; 1 microM), ATP (1 mM), isoproterenol (1 mM), dibutyryl adenosine 3',5'-cyclic monophosphate (cAMP; 1 mM), and forskolin (1 microM) was measured in muscle strips from guinea pig gastric fundus before and after treatment with NEM (5 microM) for 1 h. Protection of VIP receptors with VIP or the VIP antagonist VIP10-28 fully protected relaxation induced by VIP and by field stimulation, but did not protect relaxation induced by ATP or isoproterenol. Protection of ATP receptors with ATP protected only the response to ATP, but did not protect the response to field stimulation, VIP, or isoproterenol. Relaxation induced by either forskolin or dibutyryl cAMP was not altered by treatment with NEM alone or in the presence of protective ligands, indicating that at the concentrations used NEM inactivated membrane receptors without affecting intracellular relaxation mechanisms. These studies indicate that VIP but not ATP is the neurotransmitter responsible for neurally induced relaxation in the gastric fundus.

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Comparative Study of pA2 Values of Pirenzepine and Atropine for Guinea-Pig Gastric Fundus and Gastric Smooth Muscle

Pharmacology ◽

10.1159/000138032 ◽

1984 ◽

Vol 29 (6) ◽

pp. 329-335 ◽

Cited By ~ 4

Author(s):

Del Tacca ◽

G. Soldani ◽

C. Bernardini ◽

E. Martinotti

Keyword(s):

Smooth Muscle ◽

Guinea Pig ◽

Comparative Study ◽

Gastric Fundus ◽

Gastric Smooth Muscle

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Characterization of opioid receptors on smooth muscle cells from guinea pig stomach

AJP Gastrointestinal and Liver Physiology ◽

10.1152/ajpgi.1992.262.3.g461 ◽

1992 ◽

Vol 262 (3) ◽

pp. G461-G469 ◽

Cited By ~ 1

Author(s):

L. Zhang ◽

Z. F. Gu ◽

T. Pradhan ◽

R. T. Jensen ◽

P. N. Maton

Keyword(s):

Smooth Muscle ◽

Smooth Muscle Cells ◽

Opioid Receptors ◽

Muscle Cells ◽

Receptor Subtypes ◽

Selective Antagonist ◽

Kappa Agonist ◽

Gastric Smooth Muscle ◽

Selective Ligand ◽

Guinea Pig Stomach

On the basis of opioid-stimulated contraction of dispersed gastric smooth muscle cells it has been suggested that these cells possess opioid receptors of three subtypes: kappa (kappa), mu (mu), and delta (delta). We have used selective peptidase-resistant radioligands, agonists and antagonists, to examine receptor subtypes on dispersed gastric smooth muscle cells from guinea pigs prepared by collagenase digestion. The kappa-agonist U-50488H, the mu-agonist [D-Ala2,N-Me-Phe4,Gly5-ol]enkephalin (DAGO), and the delta-agonist [D-Pen2,Pen5]enkephalin (DPDPE) each caused muscle contraction. The concentrations required to caused half-maximal contraction were U50488H (6 pM) greater than DAGO (13 pM) greater than DPDPE (6 nM). The abilities of these agonists to inhibit binding of [3H]U-69593 (kappa-preferring) by 50% were U50488H (43 nM) greater than DAGO (43 microM) greater than DPDPE (200 microM). Their abilities to inhibit binding of [3H]naloxone (mu-preferring) by 50% were DAGO (0.2 microM) greater than U50488H (10 microM) greater than DPDPE (greater than 100 microM). No binding could be detected with the delta-selective ligand [3H]DPDPE. The kappa-preferring antagonist Mr2266 (10 nM) preferentially inhibited contraction stimulated by the kappa-agonist U50488H, and naltrexone (10 nM) (mu-selective antagonist) preferentially inhibited contraction stimulated by the mu-agonist DAGO. ICI 174864 (200 microM; delta-selective antagonist) had no effect on contraction stimulated by mu-, kappa-, or delta-agonists. Contraction stimulated by the delta-agonist DPDPE was inhibited by both kappa- and mu-receptor antagonists. Studies on the effect of the antagonists on binding of [3H]naloxone and [3H]U69593 also provided evidence for kappa- and mu-sites but nor for delta-sites.(ABSTRACT TRUNCATED AT 250 WORDS)

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