Biomedical subjects

N Muto

Publications and source records attributed to N Muto.

At least 19 recordsLinked to original sources

PubMed2001

Glucocorticoid-induced insulin resistance associates with activation of protein kinase C isoforms.

We studied glucocorticoid-induced insulin resistance and possible role of protein kinase C (PKC). Pretreatment with dexamethasone, prednisolone and corticosterone for 60 min decreased insulin-induced [3H] 2-deoxyglucose (DOG) uptake in isolated rat adipocytes. Preincubation with Go6976, LY379196 or myristoylated PKC pseudosubstrate, conventional PKC inhibitor, but not cycloheximide or RU38486, recovered dexamethasone-induced insulin resistance. Dexamethasone activated immunoprecipitates with anti-PKC alpha, beta, and zeta antibodies. PKC zeta activity in adipocytes increased to 163%, and 264% from basal level (100%) with dexamethasone and insulin treatment, respectively. Dexamethasone provoked redistribution of both PKC beta and zeta from the cytosol to the membrane. These results indicate that dexamethasone activates both conventional and atypical PKC. However, conventional PKC is more important in glucocorticoid-induced insulin resistance.

Adipocytes↗

PubMed2001

Mitogen-activated protein kinase regulates normal transition from metaphase to interphase following parthenogenetic activation in porcine oocytes.

The decrease in maturation-promoting factor (MPF) activity precedes that in mitogen-activated protein kinase (MAPK) activity after egg activation, but the cellular functions of this delayed inactivation of MAPK are still unclear. The present study was conducted to examine the essential role of MAPK activity for supporting the transition from metaphase to interphase in porcine oocytes matured in vitro. The increases in the phosphorylated forms of MAPK and the activities of MAPK and histone H1 kinase (H1K) were shown in oocytes arrested at the metaphase II (MII) stage. After additional incubation of MII-arrested oocytes in medium with added U0126, a specific inhibitor of MAPK kinase, 24% of oocytes completed the second meiotic division and underwent entry into interphase with pronucleus (PN) formation, but not second polar body (PB-2) emission. The intensities of the phosphorylated forms of MAPK and the activities of MAPK and H1K in matured oocytes treated with U0126 were significantly decreased by the treatment with U0126. Electrostimulation to induce artificial activation caused both H1K and MAPK inactivation; the inactivation of H1K preceded the inactivation of MAPK and sustained high levels of MAPK activity were detected during the period of PB-2 emission. However, the time sequence required for MAPK inactivation was significantly reduced by the addition of U0126 to the culture medium following electrostimulation, resulting in the dramatic inactivation of MAPK distinct from that of H1K. In these oocytes, PB-2 emission was markedly inhibited but little difference was found in the time course of PN formation compared with oocytes not treated with U0126. These findings suggest that the decrease in MAPK activity is partly involved in driving matured oocytes out of metaphase to induce PN development, and that the delayed MAPK inactivation after the onset of MPF inactivation in activated oocytes has a crucial role for PB-2 emission to accomplish the transition from meiosis to mitosis.

Animals↗

PubMed2001

Enhancement of developmental competence after in vitro fertilization of porcine oocytes by treatment with ascorbic acid 2-O-alpha-glucoside during in vitro maturation.

The present study was conducted to examine the effect of ascorbic acid 2-O-alpha-glucoside (AA-2G), a stable ascorbate derivative, on the sustenance of cytoplasmic maturation responsible for subsequent developmental competence after in vitro fertilization of porcine oocytes. Cumulus-oocyte complexes were cultured for 44 h in North Carolina State University 37 medium supplemented with cysteine, gonadotropins, 10% (v:v) porcine follicular fluid, and 0-750 microM AA-2G. When oocytes were matured in the presence of 250 microM AA-2G, their ability to promote transformation of the sperm nucleus into the male pronucleus (MPN) was strongly enhanced after in vitro fertilization. Similarly, the presence of 25 microM beta-mercaptoethanol (ME) enhanced the degree of progression to MPN of penetrated sperm by associating with the increase in intracellular glutathione (GSH) content. Although the AA-2G treatment during oocyte maturation showed no influence on the GSH concentration, significantly higher levels of ascorbic acid (AsA) were detected in these oocytes than in those oocytes cultured without AA-2G (P < 0.05). The length of DNA migration encompassed by reactive oxygen species (ROS), generated by the hypoxanthine-xanthine oxidase system, was not increased in the oocytes treated with AA-2G, whereas ME treatment could not block the DNA damage by ROS. These findings indicate that AA-2G in maturation medium can potentiate the cellular protection of oocytes against oxidative stress by continuously supplying AsA. The proportion of development to the blastocyst stage after in vitro insemination was significantly increased in oocytes matured with AA-2G (P < 0.05), and this proportion showed no difference in comparison with that of oocytes treated with ME. These findings suggest that a critical concentration of intracellular AsA, supplied by AA-2G during in vitro maturation, plays an important role in supporting the cytoplasmic maturation responsible for developmental competence after fertilization by prevention of oxidative stress against porcine oocytes.

Animals↗

PubMed2001

[Speech perception ability in a patient with a 8-channel auditory brainstem implant].

Auditory brainstem implant (ABI) is a central prosthesis that directly stimulates the cochlear nucleus in the brainstem for those who have interrupted auditory nerves and cannot benefit from the cochlear implantation. Speech perception in a recipient of the Nuclues 8 channel ABI, the first in Japan, is reported. A 25-year-old man with bilateral acoustic nerve tumors postlingually deafened due to tumor resection received auditory sensations with 5 channels. The correct answer using a coding strategy, SPEAK, was 35% for 5 vowels and 36% for 5 monosyllables. The use of ABI also improved his lip-reading ability on monosyllables and open-set words. This indicated that he benefited from ABI, although it was limited. Even after 1 year and 3 months of follow-up, he had no serious side effects such an infection or implant rejection.

Adult↗

PubMed2000

Cellular zinc status regulates cytomegalovirus major immediate-early promoter.

Diethylenetriaminepenta-acetic acid (DTPA) inhibits human cytomegalovirus (CMV) replication in vitro, although the mechanism has remained unclear. The present study shows that DTPA inhibits CMV major immediate-early (MIE) promoter activity in a luciferase reporter assay, whereas its enhancer-less promoter was not affected. The inhibitory effect of DTPA on CMV MIE promoter activity was abrogated by stoichiometric amounts of cations in the following (decreasing) order, Zn(2+)>Co(2+)>Ni(2+)>Cu(2+)>Fe(3+)>Fe(2+), but not by Mn(2+). These cations bind to DTPA and may limit the zinc-chelating capability. In the absence of DTPA, exogenous zinc activated CMV MIE promoter activity in a dose-dependent manner, but not its enhancer-less promoter. The intracellular metallothionein content of DTPA- and cation-treated cultures was significantly correlated with CMV MIE promoter activity. DTPA may inhibit CMV replication by regulating CMV MIE promoter activity through controlling the availability of cellular zinc. Since the CMV MIE promoter has no consensus sequence for a metal responsive element, a novel mechanism for metal-regulated transcription may be involved in this process.

Antigens, Viral↗

PubMed2000

Protection of porcine oocytes against apoptotic cell death caused by oxidative stress during In vitro maturation: role of cumulus cells.

The present study was conducted to examine the protective effect of cumulus cells on oocyte damage caused by reactive oxygen species (ROS), generated by the hypoxanthine-xanthine oxidase (XOD) system, during in vitro maturation of porcine oocytes. Cumulus-oocyte complexes (COCs) and cumulus-denuded oocytes (DOs) were cultured for 44 h in NCSU37 supplemented with cysteine, gonadotropins, 10% porcine follicular fluid, and hypoxanthine in the presence or absence of XOD. DNA cleavage and damage were analyzed using the terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL) method and single cell microgel electrophoresis (comet) assay, respectively, and caspase-3 activity and glutathione (GSH) content were measured in each experimental group. Exposure of DOs to ROS resulted in meiotic arrest and the increase of degenerated oocytes. These degenerated DOs underwent apoptosis, as shown by the TUNEL-positive reaction within their germinal vesicles and the activation of caspase-3. The length of DNA migration in DOs treated with XOD was significantly longer than that of untreated DOs (P: < 0.05). However, irreparable cell damage caused by ROS was not observed in COCs, and no difference was observed in the caspase-3 activity of both COCs treated with and without XOD. A significantly (P: < 0.05) high level of GSH was found in COCs after 44 h of culture, compared with that of oocytes freshly isolated from their follicles, whereas GSH content in DOs markedly decreased after treatment with or without XOD. These findings suggest that cumulus cells have a critical role in protecting oocytes against oxidative stress-induced apoptosis through the enhancement of GSH content in oocytes.

Animals↗

PubMed2000

Two metallothioneins in the fresh-water fish, crucian carp (Carassius cuvieri): cDNA cloning and assignment of their expression isoforms.

Two metallothionein cDNAs (MT-A and MT-B) in the fresh-water fish crucian carp (Carassius cuvieri Temminck et Schlegel) were cloned. Sequence analysis of both cDNAs gave the structure of a coding region corresponding to 60 amino acid residues. The homology of their deduced amino acid sequences was completely conserved at the positions of the cysteine residue, but a significant difference existed in the size of their 3'-untranslated regions (130 base pairs for MT-A and 280 base pairs for MT-B). Direct amino acid sequencing of the MT-II isoform purified by HPLC was accomplished for up to 30 residues and its sequence was identical to that deduced from MT-B cDNA. This is the first case in vertebrates that N-terminal methionine in crucian carp MT-II was not blocked. By northern blot analysis, basal and cadmium chloride- or dexamethasone-induced MT-B (MT-II) mRNAs were detected time dependently after treatment. On the other hand, the expression of MT-A mRNA was extremely low. These results indicate that the MT isoform II in crucian carp is coded by the MT-B gene, and that the MT-B-dominant expression of mRNA in crucian carp may be due to the difference in the 3'-untranslated regions of MT mRNAs.

Amino Acid Sequence↗

PubMed2000

Metallothionein acts as a cytoprotectant against doxorubicin toxicity.

The protective role of metallothionein (MT) against the myocardiotoxicity and hepatotoxicity of doxorubicin (Dox) was investigated in mice. Dox-induced elevations of plasma creatine kinase activity, a measure of myocardiac damage, and plasma glutamate pyruvate transaminase activity, reflecting hepatic damage, were prevented by pretreatment with an MT inducer. Pretreatment with zinc induced MT in the liver and heart, thereby reducing Dox toxicity in these two organs. Pretratment with n-hexane also induced MT and reduced Dox toxicity, but only in the liver. In primary hepatocyte cultures, the leakage of lactate dehydrogenase induced by Dox was prevented by zinc pretreatment. These results suggest that MT induction prevents Dox toxicity in vivo and in vitro. Furthermore, we determined that MT-null mice were more sensitive to the myocardiotoxic and hepatotoxic effects of Dox. These findings indicate that both basal and induced MT protect against Dox toxicity.

Alanine Transaminase↗

PubMed2000

Distinct mechanisms of transport of ascorbic acid and dehydroascorbic acid in intestinal epithelial cells (IEC-6).

Ascorbic acid (AsA) is an essential nutrient for humans as they lack its biosynthesizing key enzyme. Its absorption mechanism in small intestinal epithelial cells still remains to be resolved. In this study, the transport mechanisms functioning on the uptake of AsA and its oxidized form, dehydroascorbic acid (DHA), were investigated using rat small intestinal epithelial cell line IEC-6. Both AsA and DHA were accumulated in the cells in time- and concentration-dependent manners, but their absorption kinetics were apparently different. The saturability of AsA uptake was shown at a considerably lower concentration in IEC-6 cells as well as other mammalian cells, indicating that this absorption was mediated by a specific transporting carrier. The absorption efficiency of AsA was about 1/5-1/10 that of DHA at the same concentration range and, moreover, the uptake of DHA was almost comparable to that of 2-deoxy-D-glucose, an alternative of glucose. The uptake of AsA was diminished by the removal of sodium ion, but not by the addition of glucose, whereas that of DHA was sodium ion-independent and effectively inhibited by glucose. In addition, phlorizin and cytochalasin B, which are blockers of glucose transporters, interfered the uptake of DHA more efficiently than that of AsA. These results indicate that there are at least two distinct transport systems of vitamin C in rat small intestinal epithelial cells; AsA is transported by a specific transporter and DHA is mainly transported by glucose transporter(s).

Animals↗

PubMed1999

Apoptosis during iron chelator-induced differentiation in F9 embryonal carcinoma cells.

We have previously demonstrated that three potent iron chelators, hinokitiol, dithizone and deferoxamine, induce differentiation of F9 embryonal carcinoma cells, as do other well-known morphogens such as retinoic acid (RA) and sodium butyrate (NaB). In this study, we compared the patterns of cell proliferation, cell death and cell cycle arrest during the process of differentiation induced by these five agents. When F9 cells were cultured with the agents at their individual differentiation-inducing concentrations, cell proliferation was rapidly inhibited by treatment with the iron chelators and NaB. In contrast, RA did not influence the rate of increase of cell number at the concentration of 1 microm. The three chelators also caused a marked reduction in cell viability, and the treated cells exhibited internucleosomal DNA fragmentation, whereas cells treated with NaB showed no apoptotic characteristics. RA induced apoptosis weakly at 1 microm and strongly at higher concentrations. In addition, all the iron chelators hindered cell cycle progression, resulting in an arrest at the G1-S interface or S phase. The phenomena observed in chelator-treated cells were considerably different from those in RA- or NaB-treated cells. It is concluded that the three iron chelators cause both severe apoptotic cell death and cell cycle arrest of proliferating F9 cells via cellular iron deprivation, and that this apoptotic change may be independent of the process of differentiation.

Animals↗

PubMed1999

Induction of two major isoforms of metallothionein in crucian carp (Carassius cuvieri) by air-pumping stress, dexamethasone, and metals.

The induction of metallothionein (MT) by physical and chemical stress was assessed using the fresh-water fish, crucian carp (Carassius cuvieri Temminck et Schlegel). The fish exposed to violent air-pumping stress for 6 days revealed time-dependent induction of MT-like metal-binding proteins in both their livers and kidneys. Their hepatic contents after exposure to stress were elevated to twice the basal level with 24 h, resulting in more than a 3-fold increase at 144 h, whereas their renal contents gradually increased after 24 h and reached the same level as that in the liver around 96 h. Two major inducible proteins were purified from livers of fish exposed to stress and were shown to be MT based upon their chromatographic behavior, UV absorption spectra and their molecular weights. Consequently, they were termed ccMT-1 and ccMT-2, according to their elution sequence upon anion-exchange chromatography. Both proteins mainly bound zinc in their endogenous forms and showed different immunogenicity to rat and rabbit MTs. Dexamethasone, a potent inducer for MT synthesis in mammals, induced the production of both isoforms in crucian carp, whereas cadmium and zinc ions prominently induced the synthesis of ccMT-2. These results indicate that crucian carp have the ability to produce MTs in response to various kinds of environmental stress and that violent air-pumping stress in crucian carp may induce MT synthesis, in part, via the release of endogenous factor(s), such as glucocorticoids.

Air↗

PubMed1999

DHEA improves glucose uptake via activations of protein kinase C and phosphatidylinositol 3-kinase.

We have examined the effect of adrenal androgen, dehydroepiandrosterone (DHEA), on glucose uptake, phosphatidylinositol (PI) 3-kinase, and protein kinase C (PKC) activity in rat adipocytes. DHEA (1 microM) provoked a twofold increase in 2-[3H]deoxyglucose (DG) uptake for 30 min. Pretreatment with DHEA increased insulin-induced 2-[3H]DG uptake without alterations of insulin specific binding and autophosphorylation of insulin receptor. DHEA also stimulated PI 3-kinase activity. [3H]DHEA bound to purified PKC containing PKC-alpha, -beta, and -gamma. DHEA provoked the translocation of PKC-beta and -zeta from the cytosol to the membrane in rat adipocytes. These results suggest that DHEA stimulates both PI 3-kinase and PKCs and subsequently stimulates glucose uptake. Moreover, to clarify the in vivo effect of DHEA on Goto-Kakizaki (GK) and Otsuka Long-Evans fatty (OLETF) rats, animal models of non-insulin-dependent diabetes mellitus (NIDDM) were treated with 0.4% DHEA for 2 wk. Insulin- and 12-O-tetradecanoyl phorbol-13-acetate-induced 2-[3H]DG uptakes of adipocytes were significantly increased, but there was no significant increase in the soleus muscles in DHEA-treated GK/Wistar or OLETF/Long-Evans Tokushima (LETO) rats when compared with untreated GK/Wistar or OLETF/LETO rats. These results indicate that in vivo DHEA treatment can result in increased insulin-induced glucose uptake in two different NIDDM rat models.

Adipocytes↗

PubMed1999

Induction of apoptosis by hinokitiol, a potent iron chelator, in teratocarcinoma F9 cells is mediated through the activation of caspase-3.

Hinokitiol, a potent iron chelator, has been reported to induce differentiation in teratocarcinoma F9 cells with a reduction of viable cells. In this study, we examined the steps leading to eventual cell death by hinokitiol during differentiation. Hinokitiol induced DNA fragmentation of F9 cells in a concentration- and time-dependent manner. This effect was also observed in a cell-free system using the nuclei from intact cells and the cytosols from hinokitiol-treated cells. In contrast, hinokitiol methyl ether and hinokitiol-Fe (III) complex, which are deficient in iron-chelating activity, showed no DNA fragmentation activity in both cell culture and cell-free systems. These results suggest that iron deprivation by hinokitiol may be involved in the induction of apoptosis of F9 cells. Caspase-3, one of the key enzymes in the apoptotic cascade, was specifically activated by hinokitiol treatment, but not by the other two derivatives. In addition, its specific inhibitor, benzyloxycarbonyl-Val-Ala-Asp-fluoromethyl ketone, strongly blocked hinokitiol-induced DNA fragmentation. These results indicate that iron deprivation by hinokitiol can induce apoptosis of F9 cells through the activation of caspase-3.

Amino Acid Chloromethyl Ketones↗

PubMed1998

Tissue accumulation of cadmium following oral administration to metallothionein-null mice.

To verify the roles of intestinal metallothionein (MT) as a barrier against ingested cadmium (Cd) and as a transporter of mucosal Cd to the kidneys, the distribution of orally administered Cd was compared between normal and MT-I and -II knock-out (MT-null) mice. Following single administration of a low dose of Cd (0.1 mg/kg), hepatic Cd levels and the sum of total Cd in the liver and kidney (K + L) were significantly less in the controls than in MT-null mice. The ratio of Cd in the kidney to the liver (K/L) was significantly lower in the MT-null mice. On the other hand, at a high Cd dose (2.0 mg/kg), K + L and K/L were not significantly different between the two groups. However, following oral pretreatment with zinc (Zn) to the high dose control mice, K + L significantly decreased and K/L significantly increased. No such effects of Zn pretreatment were observed in MT-null mice. Similar differences in K + L and K/L were also observed between the control and MT-null mice groups following the Zn pretreatment. Repeated administration of Cd for 4 weeks resulted in significantly larger K/L distribution in control mice over null mice. These results suggest that MT in the intestinal mucosa functions both as a protective barrier against Cd absorption and as an extracellular transporter of Cd to the kidney.

Administration, Oral↗

PubMed1998

Requirement for cooperative interaction of interleukin-6 responsive element type 2 and glucocorticoid responsive element in the synergistic activation of mouse metallothionein-I gene by interleukin-6 and glucocorticoid.

Metallothionein (MT)-inducing activity of interleukin (IL)-6 depends on the presence of glucocorticoid in hepatic cells. The synergistic action of IL-6 and glucocorticoid was observed in the transcriptional activation of the mouse MT (mMT)-I gene. We found that a 281-bp promoter was sufficient for IL-6 and glucocorticoid stimulation. Our inspection of this region revealed the putative type 1 and 2 IL-6 responsive elements (REs). Functional analyses of these regions were performed using luciferase reporter constructs, and it was observed that the type 2 IL-6RE exerted the major response to the IL-6 signal. The transcriptional factor binding to type 1 IL-6RE, nuclear factor-IL-6, hardly contributed to the activation of the mMT-I promoter by IL-6 and glucocorticoid. A glucocorticoid responsive element (GRE) was also required for the synergistic activation by IL-6 and glucocorticoid. Interestingly, this synergism was not observed when the type 2 IL-6RE and the GRE were kept apart. Therefore, the synergistic activation of the mMT-I gene by IL-6 and glucocorticoid may require not only that signal transducers and activators 3 (Stat3) and the glucocorticoid receptor (GR) bind to their respective responsive elements, but also that Stat3 and the GR physically interact with one another.

Acute-Phase Proteins↗

PubMed1998

Induction of differentiation and apoptosis by dithizone in human myeloid leukemia cell lines.

We investigated the effect of diphenylthiocarbazone (dithizone) and its structurally related compounds on the differentiation and apoptosis of two human myeloid leukemia cell lines. Dithizone caused a time- and concentration-dependent induction of differentiation in both the promyelocytic leukemia cell line HL-60 cells and the myeloblastic leukemia cell line ML-1 cells, as measured by nitroblue tetrazolium (NBT) reducing activity. Morphological changes and esterase activities confirmed that this differentiation took place. The induction of differentiation required the addition of dithizone to the culture medium for at least 12 h. The differentiation inducing activity was inhibited by the preincubation of dithizone with various metal ions such as Pb2+, Zn2+, Cu2+ and Mn2+ ions, but not with Fe3+ and Mg2+ ions. In addition, the DNA extracted from dithizone-treated HL-60 cells showed a typical ladder pattern characteristic of apoptosis in agarose gel electrophoresis. A quantitative analysis of DNA fragmentation revealed that this apoptosis was concentration- and time-dependent in both the HL-60 and ML-1 cells. Dithizone-induced apoptosis was also inhibited by preincubation with Mn2+ ions, but not with Mg2+ ions. These results indicate that dithizone induces both differentiation and apoptosis in HL-60 and ML-1 cells through a unique mechanism including metal chelation.

Acute Disease↗

PubMed1998

Differential effect of the antidiabetic thiazolidinediones troglitazone and pioglitazone on human platelet aggregation mechanism.

Troglitazone and pioglitazone, antidiabetic thiazolidinediones, are known to improve insulin resistance. However, the effect of these drugs on platelet aggregation remains unclear. The chemical structure of troglitazone contains vitamin E. Accordingly, we studied the effect of troglitazone, pioglitazone, and vitamin E on thrombin-induced platelet aggregation, metabolism of phosphoinositide, protein phosphorylation, protein kinase C (PKC)-alpha and -beta, and phosphatidylinositol (PI) 3-kinase activation in vitro in human platelets. Maximum platelet aggregation by ADP, collagen, and thrombin decreased in the presence of 0.1-1 micromol/l troglitazone and 500 nmol/l vitamin E for 60 min compared with controls. However, pioglitazone did not inhibit ADP-, collagen-, or thrombin-induced platelet aggregation. Pretreatment with troglitazone and vitamin E, but not with pioglitazone, resulted in decreases in thrombin-induced phosphatidic acid production, hydrolysis of phosphatidylinositol 4,5-bisphosphate by phospholipase C, and 47-kDa protein phosphorylation. Thrombin-induced PKC-alpha and -beta activation in membrane fraction was suppressed by pretreatment with troglitazone and vitamin E, but not with pioglitazone. Separately, troglitazone and pioglitazone stimulated PI 3-kinase activity, but thrombin-induced PI 3-kinase activation was suppressed by pretreatment with troglitazone and pioglitazone for 60 min. These results suggest that troglitazone and vitamin E, but not pioglitazone, have a potent inhibitory effect on platelet aggregation via suppression of the thrombin-induced activation of phosphoinositide signaling in human platelets. Finally, the chemical structure of vitamin E may contribute to the inhibitory effect of troglitazone on platelet aggregation in human platelets.

Adenosine Diphosphate↗

PubMed1998

Cholecystokinin stimulates ascorbic acid secretion through its specific receptor in the perfused stomach of rats.

We have previously demonstrated that endogenous ascorbic acid is secreted into the gastric lumen by cholinergic stimulation in both conscious pylorus-ligated rats and the perfused stomach of unconscious rats, and that gastrin, a potent gastric stimulatory peptide hormone, has no effect. In the present study, the effects of some gastrointestinal peptide hormones on gastric ascorbic acid secretion were further examined in the perfused stomach of rats. An intravenous administration of cholecystokinin octapeptide (CCK-8) significantly increased gastric ascorbic acid secretion at a dose of 1.0 and 4.0 micrograms/kg, whereas the other three peptides examined, bombesin, neurotensin and substance P, showed no or little effect at the doses which were quite commonly employed for evaluation of various gastric functions. CCK-8-induced ascorbic acid secretion was reduced by pretreatment with proglumide, which is a CCK receptor antagonist, but not by pretreatment with atropine. These results indicate that gastric ascorbic acid secretion is physiologically regulated not only by muscarinic receptor-associated cholinergic stimulation but also by CCK receptor-associated humoral stimulation.

Animals↗