Ca2+ entry through reverse Na+ /Ca2+ exchanger in NCI-H716, glucagon-like peptide-1 secreting cells

Glucagon like peptide-1 (GLP-1) released from enteroendocine L-cells in the intestine has incretin effects due to its ability to amplify glucose-dependent insulin secretion. Promotion of an endogenous release of GLP-1 is one of therapeutic targets for type 2 diabetes mellitus. Although the secretion of GLP-1 in response to nutrient or neural stimuli can be triggered by cytosolic Ca2+ elevation, the stimulussecretion pathway is not completely understood yet. Therefore, the aim of this study was to investigate the role of reverse Na+ /Ca2+ exchanger (rNCX) in Ca2+ entry induced by muscarinic stimulation in NCI-H716 cells, a human enteroendocrine GLP-1 secreting cell line. Intracellular Ca2+ was repetitively oscillated by the perfusion of carbamylcholine (CCh), a muscarinic agonist. The oscillation of cytosolic Ca2+ was ceased by substituting extracellular Na+ with Li + or NMG + . KB-R7943, a specific rNCX blocker, completely diminished CCh-induced cytosolic Ca2+ oscillation. Type 1 Na+ /Ca2+ exchanger (NCX 1 ) proteins were expressed in NCI-H716 cells. These results suggest that rNCX might play a crucial role in Ca2+ entry induced by cholinergic stimulation in NCIH716 cells, a GLP-1 secreting cell line.

Comparison of the Autism Diagnostic Observation Schedule and Childhood Autism Rating Scale in the Diagnosis of Autism Spectrum Disorder: A Preliminary Study

OBJECTIVES: We examined the agreement between the Autism Diagnostic Observation Schedule (ADOS) and the Childhood Autism Rating Scale (CARS) in the diagnosis of autism spectrum disorder. METHODS: The ADOS and CARS scores of 78 children were retrospectively collected from a chart review. A correlation analysis was performed to examine the concurrent validity between the two measures. Using the receiver operating characteristic (ROC) curve, we determined the optimal cut-off score of the CARS for identifying autism spectrum disorder. RESULTS: The CARS score was significantly correlated with the ADOS score (r=0.808, p < 0.001). Taking ADOS as the ideal standard, the optimal cut-off scores of CARS for identifying autism and autism spectrum were 30 and 24.5, respectively. CONCLUSION: We determined the optimal cut-off scores of CARS for screening and diagnosing autism spectrum disorder.

Intravenous Anesthetic, Propofol Affects Synaptic Responses in Cerebellar Purkinje Cells

OBJECTIVE: Propofol is an intravenously administered anesthetic that enhances γ-aminobutyric acid-mediated inhibition in the central nerve system. Other mechanisms may also be involved in general anesthesia. Propofol has been implicated in movement disorders. The cerebellum is important for motor coordination and motor learning. The aim of the present study was to investigate the propofol effect on excitatory synaptic transmissions in cerebellar cortex. METHODS: Excitatory postsynaptic currents by parallel fiber stimulation and complex spikes by climbing fiber stimulation were monitored in Purkinje cells of Wister rat cerebellar slice using whole-cell patch-clamp techniques. RESULTS: Decay time, rise time and amplitude of excitatory postsynaptic currents at parallel fiber Purkinje cell synapses and area of complex spikes at climbing fiber Purkinje cell synapses were significantly increased by propofol administration. CONCLUSION: The detected changes of glutamatergic synaptic transmission in cerebellar Purkinje cell, which determine cerebellar motor output, could explain cerebellar mechanism of motor deficits induced by propofol.

Hydrogen peroxide inhibits Ca²⁺ efflux through plasma membrane Ca²⁺-ATPase in mouse parotid acinar cells

Intracellular Ca²⁺ mobilization is closely linked with the initiation of salivary secretion in parotid acinar cells. Reactive oxygen species (ROS) are known to be related to a variety of oxidative stress-induced cellular disorders and believed to be involved in salivary impairments. In this study, we investigated the underlying mechanism of hydrogen peroxide (H₂O₂) on cytosolic Ca²⁺ accumulation in mouse parotid acinar cells. Intracellular Ca²⁺ levels were slowly elevated when 1 mM H₂O₂ was perfused in the presence of normal extracellular Ca²⁺. In a Ca²⁺-free medium, 1 mM H₂O₂ still enhanced the intracellular Ca²⁺ level. Ca²⁺ entry tested using manganese quenching technique was not affected by perfusion of 1 mM H₂O₂. On the other hand, 10 mM H₂O₂ induced more rapid Ca²⁺ accumulation and facilitated Ca²⁺ entry from extracellular fluid. Ca²⁺ refill into intracellular Ca²⁺ store and inositol 1,4,5-trisphosphate (1 µM)-induced Ca²⁺ release from Ca²⁺ store was not affected by 1 mM H₂O₂ in permeabilized cells. Ca²⁺ efflux through plasma membrane Ca²⁺-ATPase (PMCA) was markedly blocked by 1 mM H₂O₂ in thapsigargin-treated intact acinar cells. Antioxidants, either catalase or dithiothreitol, completely protected H₂O₂-induced Ca²⁺ accumulation through PMCA inactivation. From the above results, we suggest that excessive production of H₂O₂ under pathological conditions may lead to cytosolic Ca²⁺ accumulation and that the primary mechanism of H₂O₂-induced Ca²⁺ accumulation is likely to inhibit Ca²⁺ efflux through PMCA rather than mobilize Ca²⁺ ions from extracellular medium or intracellular stores in mouse parotid acinar cells.

Hydrogen peroxide attenuates refilling of intracellular calcium store in mouse pancreatic acinar cells

Intracellular calcium (Ca²⁺) oscillation is an initial event in digestive enzyme secretion of pancreatic acinar cells. Reactive oxygen species are known to be associated with a variety of oxidative stress-induced cellular disorders including pancreatitis. In this study, we investigated the effect of hydrogen peroxide (H₂O₂) on intracellular Ca²⁺ accumulation in mouse pancreatic acinar cells. Perfusion of H₂O₂ at 300 µM resulted in additional elevation of intracellular Ca²⁺ levels and termination of oscillatory Ca²⁺ signals induced by carbamylcholine (CCh) in the presence of normal extracellular Ca²⁺. Antioxidants, catalase or DTT, completely prevented H₂O₂-induced additional Ca²⁺ increase and termination of Ca²⁺ oscillation. In Ca²⁺-free medium, H₂O₂ still enhanced CCh-induced intracellular Ca²⁺ levels and thapsigargin (TG) mimicked H₂O₂-induced cytosolic Ca²⁺ increase. Furthermore, H₂O₂-induced elevation of intracellular Ca²⁺ levels was abolished under sarco/endoplasmic reticulum Ca²⁺ ATPase-inactivated condition by TG pretreatment with CCh. H₂O₂ at 300 µM failed to affect store-operated Ca²⁺ entry or Ca²⁺ extrusion through plasma membrane. Additionally, ruthenium red, a mitochondrial Ca²⁺ uniporter blocker, failed to attenuate H₂O₂-induced intracellular Ca²⁺ elevation. These results provide evidence that excessive generation of H₂O₂ in pathological conditions could accumulate intracellular Ca²⁺ by attenuating refilling of internal Ca²⁺ stores rather than by inhibiting Ca²⁺ extrusion to extracellular fluid or enhancing Ca²⁺ mobilization from extracellular medium in mouse pancreatic acinar cells.

Ca(2+)-induced Ca2+ Release from Internal Stores in INS-1 Rat Insulinoma Cells

The secretion of insulin from pancreatic beta-cells is triggered by the influx of Ca2+ through voltage-dependent Ca2+ channels. The resulting elevation of intracellular calcium ([Ca2+]i) triggers additional Ca2+ release from internal stores. Less well understood are the mechanisms involved in Ca2+ mobilization from internal stores after activation of Ca2+ influx. The mobilization process is known as calcium-induced calcium release (CICR). In this study, our goal was to investigate the existence of and the role of caffeine-sensitive ryanodine receptors (RyRs) in a rat pancreatic beta-cell line, INS-1 cells. To measure cytosolic and stored Ca2+, respectively, cultured INS-1 cells were loaded with fura-2/AM or furaptra/AM. [Ca2+]i was repetitively increased by caffeine stimulation in normal Ca2+ buffer. However, peak [Ca2+]i was only observed after the first caffeine stimulation in Ca2+ free buffer and this increase was markedly blocked by ruthenium red, a RyR blocker. KCl-induced elevations in [Ca2+]i were reduced by pretreatment with ruthenium red, as well as by depletion of internal Ca2+ stores using cyclopiazonic acid (CPA) or caffeine. Caffeine-induced Ca2+ mobilization ceased after the internal stores were depleted by carbamylcholine (CCh) or CPA. In permeabilized INS-1 cells, Ca2+ release from internal stores was activated by caffeine, Ca2+, or ryanodine. Furthermore, ruthenium red completely blocked the CICR response in permeabilized cells. RyRs were widely distributed throughout the intracellular compartment of INS-1 cells. These results suggest that caffeine-sensitive RyRs exist and modulate the CICR response from internal stores in INS-1 pancreatic beta-cells.

Alteration of Ryanodine-receptors in Cultured Rat Aortic Smooth Muscle Cells

Vascular smooth muscle cells can obtain a proliferative function in environments such as atherosclerosis in vivo or primary culture in vitro. Proliferation of vascular smooth muscle cells is accompanied by changes in ryanodine receptors (RyRs). In several studies, the cytosolic Ca2+ response to caffeine is decreased during smooth muscle cell culture. Although caffeine is commonly used to investigate RyR function because it is difficult to measure Ca2+ release from the sarcoplasmic reticulum (SR) directly, caffeine has additional off-target effects, including blocking inositol trisphosphate receptors and store-operated Ca2+ entry. Using freshly dissociated rat aortic smooth muscle cells (RASMCs) and cultured RASMCs, we sought to provide direct evidence for the operation of RyRs through the Ca2+- induced Ca2+-release pathway by directly measuring Ca2+ release from SR in permeabilized cells. An additional goal was to elucidate alterations of RyRs that occurred during culture. Perfusion of permeabilized, freshly dissociated RASMCs with Ca2+ stimulated Ca2+ release from the SR. Caffeine and ryanodine also induced Ca2+ release from the SR in dissociated RASMCs. In contrast, ryanodine, caffeine and Ca2+ failed to trigger Ca2+ release in cultured RASMCs. These results are consistent with results obtained by immunocytochemistry, which showed that RyRs were expressed in dissociated RASMCs, but not in cultured RASMCs. This study is the first to demonstrate Ca2+ release from the SR by cytosolic Ca2+ elevation in vascular smooth muscle cells, and also supports previous studies on the alterations of RyRs in vascular smooth muscle cells associated with culture.

Endothelial Dysfunction in the Smokers Can Be Improved with Oral Cilostazol Treatment

BACKGROUND: Smoking is one of well known environmental factors causing endothelial dysfunction and plays important role in the atherosclerosis. We investigated the effect of cilostazol could improve the endothelial dysfunction in smokers with the measurement of flow-mediated dilatation (FMD). METHODS: We enrolled 10 normal healthy male persons and 20 male smokers without any known cardiovascular diseases. After measurement of baseline FMD, the participants were medicated with oral cilostazol 100 mg bid for two weeks. We checked the follow up FMD after two weeks and compared these values between two groups. RESULTS: There was no statistical difference of baseline characteristics including age, body mass index, serum cholesterol profiles, serum glucose and high sensitive C-reactive protein between two groups. However, the control group showed significantly higher baseline endothelium-dependent dilatation (EDD) after reactive hyperemia (12.0 +/- 4.5% in the control group vs. 8.0 +/- 2.1% in the smoker group, p = 0.001). However, endothelium-independent dilatation (EID) after sublingual administration of nitroglycerin was similar between the two groups (13.6 +/- 4.5% in the control group vs. 11.9 +/- 4.9% in the smoker group, p = 0.681). Two of the smoker group were dropped out due to severe headache. After two weeks of cilostazol therapy, follow-up EDD were significantly increased in two groups (12.0 +/- 4.5% to 16.1 +/- 3.7%, p = 0.034 in the control group and 8.0 +/- 2.1% to 12.2 +/- 5.1%, p = 0.003 in the smoker group, respectively). However, follow up EID value was not significantly increased compared with baseline value in both groups (13.6 +/- 4.5% to 16.1 +/- 3.7%, p = 0.182 in the control group and 11.9 +/- 4.9% to 13.7 +/- 4.3%, p = 0.430 in the smoker group, respectively). CONCLUSION: Oral cilostazol treatment significantly increased the vasodilatory response to reactive hyperemia in two groups. It can be used to improve endothelial function in the patients with endothelial dysfunction caused by cigarette smoking.

Caffeine and 2-Aminoethoxydiphenyl Borate (2-APB) Have Different Ability to Inhibit Intracellular Calcium Mobilization in Pancreatic Acinar Cell

Inositol 1,4,5-trisphosphate receptors (InsP3Rs) modulate Ca2+ release from intracellular Ca2+ store and are extensively expressed in the membrane of endoplasmic/sarcoplasmic reticulum and Golgi. Although caffeine and 2-aminoethoxydiphenyl borate (2-APB) have been widely used to block InsP3Rs, the use of these is limited due to their multiple actions. In the present study, we examined and compared the ability of caffeine and 2-APB as a blocker of Ca2+ release from intracellular Ca2+ stores and Ca2+ entry through store-operated Ca2+ (SOC) channel in the mouse pancreatic acinar cell. Caffeine did not block the Ca2+ entry, but significantly inhibited carbamylcholine (CCh)-induced Ca2+ release. In contrast, 2-APB did not block CCh-induced Ca2+ release, but remarkably blocked SOC-mediated Ca2+ entry at lower concentrations. In permeabilized acinar cell, caffeine had an inhibitory effect on InsP3-induced Ca2+ release, but 2-APB at lower concentration, which effectively blocked Ca2+ entry, had no inhibitory action. At higher concentrations, 2-APB has multiple paradoxical effects including inhibition of InsP3-induced Ca2+ release and direct stimulation of Ca2+ release. Based on the results, we concluded that caffeine is useful as an inhibitor of InsP3R, and 2-APB at lower concentration is considered a blocker of Ca2+ entry through SOC channels in the pancreatic acinar cell.

A Successful Primary Percutaneous Coronary Intervention Twelve Days After a Cabrol Composite Graft Operation in Marfan Syndrome

The Cabrol procedure is one of several techniques used for re-implantation of a coronary artery. After replacement of the ascending aorta and aortic valve using a composite graft, second Dacron tube grafts are used for anastomosis between the ascending aortic graft and the coronary arteries. Ostial stenosis is one of the complications associated with the Cabrol operation. However, there have been no reported cases of acute thrombosis of a Cabrol graft. Here we report a case with acute ST elevation myocardial infarction due to thrombotic total occlusion of a right Cabrol graft-to-right coronary artery (RCA) twelve days after surgery in a patient with Marfan syndrome. He was successfully treated with primary percutaneous coronary intervention (PCI).

Causative factors for time delays in patients with acute st-segment elevation myocardial infarction undergoing primary percutaneous coronary intervention / 대한내과학회지

BACKGROUND/AIMS: The time delay for a patient from the onset of disease symptoms until the reperfusion therapy is one of the biggest interruptions in early reperfusion therapy in patients with acute ST-segment elevation myocardial infarction (STEMI). Here, we evaluated both the duration and nature of these time delays to facilitate early patient reperfusion therapy. METHODS: Patients with acute STEMI who were undergoing primary percutaneous coronary intervention (PCI) were prospectively enrolled in the Chungnam National University Hospital from January 2005 to December 2007. RESULTS: From a total 364 patients (mean age: 64+/-12 years) the mean time interval from the onset of symptoms to the decision to visit a hospital was 101.4+/-10.6 (median: 50.0) minutes. The mean time interval for the onset of disease symptoms to the patient arrival at the emergency room (ER) (pre-hospital delay) was 222.1+/-12.4 (median: 171.5) minutes. The mean time interval from the ER to reperfusion (door to balloon time) was 89.0+/-6.0 (median 65.0) minutes. The mean time interval from the onset of symptoms to successful reperfusion therapy (pain to balloon time) was 311+/-13.6 (median: 250) minutes. The factors associated with these significant time delays were mainly: residency in rural areas, the use of private transport in preference to an ambulance and finally the transferal of patients from other hospitals. As a result of multivariate analysis the latter was found to be the most significant causative factor. CONCLUSIONS: This study demonstrates that there is a significant pre-hospital time delay in patients with STEMI. Thus, a media campaign explaining STEMI symptoms, the importance of early visits to the emergency department, the use of an ambulance, and the activation of the base hospital for efficient patient transfer (particularly in rural areas) may reduce this time delay in patients with STEMI and avoid interruptions to otherwise efficient reperfusion therapies.

Tumor Suppressor Serine/Threonine Kinase LKB1 Expression, Not Kinase Activity, Increased in the Vascular Smooth Muscle Cells and Neointima in the Rat Carotid Artery Injury Model

BACKGROUND AND OBJECTIVES: Vascular smooth muscle cell (VSMC) proliferation is responsible for the restenosis of previously inserted coronary stents. Angiotensin II (Ang II) is known to regulate VSMC proliferation. LKB1, a serine/threonine kinase, interacts with the p53 pathway and acts as a tumor suppressor. MATERIALS AND METHODS: We assessed the association of Ang II and the expression of LKB1 in primary cultured murine VSMCs and neointima of the Sprague Dawley rat carotid artery injury model. We created carotid balloon injuries and harvested the injured carotid arteries 14 days after the procedure. RESULTS: Ang II increased LKB1 expression in a time-dependent manner and peaked at an Ang II concentration of 10(-7) mole/L in VSMCs. In the animal experiment, neointima was markedly increased after balloon injury compared to the control group. Immunohistochemical studies showed that LKB1 expression increased according to neointima thickness. Ang II augmented LKB1 expression after the injury. Western blot analysis of LKB1 with carotid artery lysate revealed the same pattern as LKB1 immunohistochemistry. Increased LKB1 expression started at 5 days after the balloon injury, and peaked at 14 days after the injury. Although LKB1 expression was increased after the injury, LKB1 kinase activity was not increased. Ang II or balloon-injury increased the expression of LKB1 although the LKB1 activity was reduced. CONCLUSION: Ang II increased LKB1 expression in VSMCs and neointima. These findings were not kinase dependant.

Usefulness of Mitral Annular Systolic Velocity in the Detection of Left Ventricular Systolic Dysfunction: Comparison with Three Dimensional Echocardiographic Data

BACKGROUND: Although the modified Simpson's method is widely used for the assessment of left ventricular ejection fraction (LVEF), it has limitations including relatively high inter- and intra-observer variability and time consuming nature. We want to evaluate whether assessing mitral annular systolic velocity (S' velocity) by tissue Doppler imaging (TDI) can be used to evaluate LV systolic function with comparing LVEF by three dimensional echocardiography (3DE). METHODS: We examined 3DE and TDI studies of patients between January and August 2008. 3DE LVEF was measured by offline commercial computer software EchoPac PC(R) (GE, Andover, MA, USA). S' velocity was obtained from the medial side with apical four chamber view by pulsed-wave Doppler with TDI. RESULTS: We included 125 patients (78 males (62.4%), mean age: 57.5+/-13.0 years). The mean S' velocity was 7.7+/-1.9 cm/s and the mean LVEF was 57.2+/-10.4%. The S' velocity measured by TDI showed a linear correlation with LVEF measured by 3DE (r=0.688, p<0.001). Study patients were divided into two groups according to the presence of LV systolic dysfunction: Group I (normal LVEF), n=102 and Group II (LVEF <50%), n=23. For prediction of significant LV systolic dysfunction by the receiver operating characteristic curve according to S' velocity, the optimal cutoff value was 6.8 cm/s. At this cutoff value, the sensitivity and specificity were 94.1% and 87%, respectively. CONCLUSION: In this study, S' velocity measured by TDI showed a significant correlation with three dimensional LVEF and can be used to detect patients with LV systolic dysfunction.

Thrombotic Occlusion of the Radial Artery as a Complication of the Transradial Coronary Intervention

No abstract available.

Intracoronary Catheter Aspiration Can Be an Adequate Option in Patients with Acute Myocardial Infarction Caused by Left Atrial Myxoma

Cardiac myxomas are the most common benign cardiac tumors and can be associated with systemic embolization including acute myocardial infarction (AMI). The probability of an arterial embolization is closely related to a tumor's villous morphology. In cases of AMI caused by cardiac myxoma, open heart surgery including excision of the coronary artery has been the one of the treatment options for removing the myxoma and embolus from the coronary artery to maintain distal coronary flow. However, preparing for emergent open heart surgery takes a considerable amount of time. Moreover, this time delay can deteriorate the coronary perfusion to the infarcted area and is associated with poor clinical prognosis. So intracoronary catheter aspiration can be an additional option to maintain the distal coronary flow. In this report we present a case with acute anterior ST elevation myocardial infarction caused by a left atrial myxoma. The embolus in the left anterior descending coronary artery was successfully removed with intracoronary catheter aspiration, and distal coronary flow was restored after the procedure.

Abnormal Expression of Neuropeptide Y in the Cerebellar Purkinje Cells of the Ataxic Mutant Mice, Pogo / 체질인류학회지

The pogo mouse is an autosomal recessive ataxic mutant that arose spontaneously in the inbred KJR/MsKist strain derived originally from Korean wild mice. The ataxic phenotype is characterized by difficulty in maintaining posture and the consequent inability to walk straight. In our previous study about pogo mice cerebellum, we reported the Purkinje cell abnormalities and ectopic expression of tyrosine hydroxylase (TH) in Purkinje cell. In this study, we have provided an abnormal expression of NPY in ataxic mutant pogo mice for the first time. There was increased immunoreactivity for NPY in Purkinje cell of ataxic pogo (pogo/pogo) mice compared to those of heterozygote non-ataxic pogo mice (pogo/+, control group). In our previous study, TH is also expressed abnormally in Purkinje cells of ataxic mutant pogo (pogo/pogo) mouse cerebellum. To compare the expression patterns of TH and NPY within some Purkinje cell using double immunofluorescence, most of NPY-immunoreactive Purkinje cells in the ataxic pogo mice are TH-immunoreactive Purkinje cells. However, all of TH-immunoreactive Purkinje cells are not express the NPY. These data reveal that abnormal NPY-immunoreactivity in the ataxic pogo (pogo/pogo) cerebellum is restricted to a subset of cells within the ectopic TH-immunoreactive Purkinje cell subset. These results further suggest that Purkinje cell abnormalities contribute to motor ataxia in the ataxic pogo mouse.

Effects of gamma-Aminobutyric Acid on Intrinsic Cholinergic Action in Exocrine Secretion of Isolated, Perfused Rat Pancreas

gamma-Aminobutyric acid (GABA) has been reported to enhance exocrine secretion evoked not only by secretagogues but also by intrinsic neuronal excitation in the pancreas. The pancreas contains cholinergic neurons abundantly that exert a stimulatory role in exocrine secretion. This study was undertaken to examine effects of GABA on an action of cholinergic neurons in exocrine secretion of the pancreas. Intrinsic neurons were excited by electrical field stimulation (EFS; 15 V, 2 msec, 8 Hz, 45 min) in the isolated, perfused rat pancreas. Tetrodotoxin or atropine was used to block neuronal or cholinergic action. Acetylcholine was infused to mimic cholinergic excitation. GABA (30microM) and muscimol (10microM), given intra-arterially, did not change spontaneous secretion but enhanced cholecystokinin (CCK; 10 pM) -induced secretions of fluid and amylase. GABA (3, 10, 30microM) further elevated EFS-evoked secretions of fluid and amylase dose-dependently. GABA (10, 30, 100microM) also further increased acetylcholine (5microM) -induced secretions of fluid and amylase in a dose-dependent manner. Bicuculline (10microM) effectively blocked the enhancing effects of GABA (30microM) on the pancreatic secretions evoked by either EFS or CCK. Both atropine (2microM) and tetrodotoxin (1microM) markedly reduced the GABA (10microM) -enhanced EFS- or CCK-induced pancreatic secretions. The results indicate that GABA enhances intrinsic cholinergic neuronal action on exocrine secretion via the GABAA receptors in the rat pancreas.

Roles of Gonadal Steroids on Exocrine Secretion of Isolated Perfused Rat Pancreas

To clarify the roles of gonadal steroids on pancreatic exocrine secretion, effects of progesterone and estradiol-17beta on spontaneous and secretagogue-induced exocrine response of isolated perfused rat pancreas were investigated. Intra-arterial infusion of progesterone resulted in significant increase of the spontaneous pancreatic fluid and amylase secretion dose-dependently. However, estradiol-17beta did not exert any influence on spontaneous pancreatic exocrine secretion. Exogenous secretin, cholecystokinin (CCK), and acetylcholine markedly stimulated pancreatic fluid and amylase secretion. Progesterone initially enhanced secretin-induced amylase secretion, but this stimulatory response declined thereafter to basal value. Moreover, secretin-induced fluid secretion was not affected by infusion of progesterone. Therefore, initial increase of secretion-induced amylase secretion by progesterone seems to be a non-specific action by washout effect of secretin. Estradiol-17beta failed to change the secretin-induced fluid and amylase secretion. Both progesterone and estradiol-17beta did not exert any influence on CCK-induced fluid and amylase secretion. Acetylcholine-induced exocrine secretion of isolated perfused pancreas also was not affected by intra-arterial infusion of progesterone or estradiol-17beta. It is concluded from the above results that progesterone could enhance the spontaneous pancreatic fluid and amylase secretion of isolated perfused rat pancreas through non-genomic short- term action, and that these effects could be masked by more potent stimulants such as secretin, CCK, and acetylcholine.

Effects of gamma-Aminobutyric Acid on Pancreatic Amylase Secretion Evoked by Sodium Oleate in Anesthetized Rats

gamma-Aminobutyric Acid (GABA) is contained in pancreatic islet beta-cells although its physiological role in pancreatic exocrine function is completely unknown at the present time. Recently, we have reported that exogenous GABA enhances secretagogue-evoked exocrine secretion in the isolated, perfused rat pancreas. This study was aimed to investigate an effect of exogenous GABA on pancreatic exocrine secretion in vivo evoked by intestinal stimulation. Rats were anesthetized with urethane (1.4 g/kg) after 24-h fast with free access to water. GABA (10, 30 and 100micromol/kg/h), given intravenously, did not change spontaneous pancreatic amylase secretion but dose-dependently elevated the amylase secretion evoked by intraduodenal sodium oleate (0.05 mmol/h). GABA (30micromol/kg/h) also further increased the amylase secretion stimulated by CCK+(30 pmol/kg/h) plus secretin (20 pmol/kg/h) but failed to modify the amylase secretion induced by secretin alone. GABA (10, 30 and 100micromol/kg/h) also dose-dependently elevated pancreatic amylase secretion evoked by CCK+alone. Bicuculline (100micromol/kg/h), a GABAA-receptor antagonist, markedly reduced the GABA-enhanced pancreatic responses to sodium oleate, CCK+plus secretin or CCK+alone. The results indicate that GABA enhances the sodium oleate-evoked pancreatic amylase secretion via GABAA-receptors in anesthetized rats, which may account for elevating the action of CCK+released by sodium oleate.

Effects of GABA on pancreatic exocrine secretion of rats

Since GABA and its related enzymes had been determined in beta-cells of pancreas islets, effects of GABA on pancreatic exocrine secretion were investigated in the isolated perfused rat pancreas. GABA, given intra-arterially at concentrations of 3, 10, 30 and 100 microM, did not exert any influence on spontaneous or secretin (12 pM)-induced pancreatic exocrine secretion. However, GABA further elevated cholecystokinin (10 pM)-, gastrin-releasing peptide (100 pM)- or electrical field stimulation-induced pancreatic secretions of fluid and amylase, dose-dependently. The GABA-enhanced CCK-induced pancreatic secretions were completely blocked by bicuculline (10 microM), a GABAA receptor antagonist but not affected by saclofen (10 microM), a GABA(B) receptor antagonist. The enhancing effects of GABA (30 microM) on CCK-induced pancreatic secretions were not changed by tetrodotoxin (1 microM) but partially reduced by cyclo-(7-aminoheptanonyl-Phe-D-Trp-Lys-Thr[BZL]) (10 microM), a somatostatin antagonist. In conclusion, GABA enhances pancreatic exocrine secretion induced by secretagogues, which stimulate enzyme secretion predominantly, via GABA(A) receptors in the rat pancreas. The enhancing effect of GABA is partially mediated by inhibition of islet somatostatin release. GABA does not modify the activity of intrapancreatic neurons.