Transport of zinc-65 at the blood-brain barrier during short cerebrovascular perfusion in the rat: its enhancement by histidine

Zinc-65 transport into different regions of rat brain has been measured during short vascular perfusion of one cerebral hemisphere with an oxygenated HEPES-containing physiological saline at pH 7.40. The [Zn2+] was buffered with either bovine serum albumin or histidine. In each case uptake was linear with time up to 90 s. 65Zn flux into brain in the presence of albumin followed Michaelis-Menten kinetics and for parietal cortex had a Km of 16 nM and a Vmax of 44 nmol/kg/min. Increasing concentrations of L-histidine enhanced 65Zn flux into brain at [Zn2+] values between 1 and 1,000 nM. The combined effect of [histidine] and [Zn2+] was best accounted for by a function of [ZnHis+], i.e., flux = 64.4.[ZnHis+]/(390 + [ZnHis+]) + 0.00378.[ZnHis+], with concentrations being nanomolar. D-Histidine had an influence similar to that of L-histidine. 65Zn flux in the presence of 100 microM L-histidine was not affected by either 500 microM L-arginine or 500 microM L-phenylanine. The results indicate specific transport of Zn2+ across the plasma membranes of brain endothelium. The enhancement due to histidine has been attributed to diffusion of ZnHis+ across unstirred layers "ferrying" zinc to and from transport sites.

Signal intensity of brain metastases on T2-weighted images: specificity for metastases from colonic cancers

In this report, we present and discuss the signal intensity of brain metastases from colon cancer on both T1- and T2-weighted images. In five of 6 cases, metastases were seen as markedly hypointense areas on T2-weighted images. This finding should alert one to the possibility of a primary cancer of the colon. Some haemorrhagic metastases from other malignancies also showed marked hypointensity. They usually exhibited hyperintensity on T1-weighted images. A case of colon metastasis was also haemorrhagic, and in this case a hyperintense area was observed on T1-weighted images. The marked hypointense area corresponded to peripheral necrosis and probably some viable tumour. Aetiologically, such hypointensity was not induced by severe fibrosis, calcification or excessive iron deposition.

Effect of etodolac on type-II collagen-induced arthritis in mice

We tested the effect of etodolac on the development of type-II collagen-induced arthritis in DBA/1J mice. It was administered orally once daily for 35 days after the primary immunization with type-II collagen. Etodolac (10 mg/kg) significantly inhibited the development of signs of arthritis on day 28 to day 35. Indomethacin (1 mg/kg) also significantly inhibited it on day 29 to day 34. Radiographic examination showed that etodolac (10 mg/kg) significantly prevented the development of osteopenia, bone erosion and new bone formation of the joints on day 35, while indomethacin (1 mg/kg) significantly prevented only the development of bone erosion. Histopathological examination showed that both etodolac (10 mg/kg) and indomethacin (1 mg/kg) significantly prevented the development of synovitis, erosion of cartilage of the joints and bone destruction of the limbs on day 35. Etodolac and indomethacin did not affect the serum level of anti-type-II collagen antibodies. These results suggest that etodolac and indomethacin suppress type-II collagen-induced arthritis without affecting humoral immune responses.

[MR imaging of postoperative change of dura mater of rabbits--effect of contrast enhancement of dura mater & correlation with pathological findings]

To explain the mechanism of benign postoperative dural enhancement, the author made experimental model of rabbit's subdural hematoma and performed magnetic resonance (MR) imaging with gadolinium-diethylenetriaminepentaacetic acid (Gd-DTPA). On plain T1-weighted images, infused blood or red blood cells could not be detected immediately after surgery. On follow up plain T1-weighted images, the infused blood could be identified in only a case with 1 cc blood infusion. Marked dural enhancement could be seen immediately after surgery and continued three to fourteen days after 1 cc or 0.1 cc blood or 0.1 cc red blood cells infusion. To the contrary, no definite dural enhancement could be seen in the cases with plasma or saline infusion. Subdural red blood cells were required for dural enhancement immediately after surgery. Pathological findings revealed three types of reaction to infused blood: newly formed capillarization with fresh hemorrhage from the capillaries; subdural hematoma and no reaction. After vanishment of dural enhancement, pathological findings of the specimens were identical to that of normal dura. Dural enhancement may be induced by increased permeability of the dura associated with subdural hematoma and/or the extravasation of the contrast from newly formed capillaries.

Rate of 59Fe uptake into brain and cerebrospinal fluid and the influence thereon of antibodies against the transferrin receptor

Uptake of 59Fe from blood into brains of anaesthetized rats and mice has been studied by intravenous infusion of [59Fe]ferrous ascorbate or of 59Fe-transferrin, the results not being significantly different. Uptakes in the rat were linear with time, but increased at longer times in the mouse. Transfer constants, K(in) (in ml/g/h x 10(3)), for cerebral hemispheres were 5.2 in the adult rat and 5.6 in the mouse. These K(in) values corresponded to 59Fe influxes of 145 and 322 pmol/g/h, respectively. 59Fe uptake into the mouse brain occurred in the following order: cerebellum > brainstem > frontal cerebral cortex > parietal cortex > occipital cortex > hippocampus > caudate nucleus. In genetically hypotransferrinaemic mice, 59Fe uptake into brain was 80-95 times greater than in To strain mice. Pretreatment of young rats and mice with monoclonal antibodies to transferrin receptors, i.e., the anti-rat immunoglobulin G OX 26 and the anti-mouse immunoglobulin M RI7 208, inhibited 59Fe uptake into spleen by 94% and 98%, respectively, indicating saturation of receptors. The antibodies reduced 59Fe uptake into rat brain by 35-60% and that into mouse brain by 65-85%. Although a major portion of iron transport across the blood-brain barrier is normally transferrin-mediated, non-transferrin-bound iron readily crosses it at low serum transferrin levels.

Electron microscopic study of intercellular junctions in human gastric mucosa with special reference to their relationship to gastric ulcer

The development of gap junctions in the human gastric mucosa has been examined to see if there is any relation to gastric ulcer. Freeze fracture replicas were prepared from the endoscopic biopsy specimens of 20 patients with gastric ulcer (15 men and five women, aged 49 (13) years) and seven healthy volunteers (four men and three women, aged 41 (19) years). Large fractured areas of lateral cell membranes of surface mucous cells were observed randomly at a direct magnification of 15,000 using electron microscopy. Small gap junctions were observed between gastric surface mucous cells in all healthy volunteers. Gap junctions in the patients with gastric ulcer were significantly fewer than in the healthy volunteers. In addition, gap junctions in patients with recurrent ulcer were significantly fewer than in those with first onset ulcer. There was no obvious relationship between age and the development of gap junctions in patients with gastric ulcer or in healthy volunteers. In areas of intestinal metaplasia, gap junctions were occasionally seen between absorptive cells of the villi, but not in the lateral membranes of goblet cells. These findings suggest that loss of intercellular communication via gap junctions is associated with gastric ulcer formation.

Post-irradiation protective effect of irsogladine maleate on intestinal crypt stem cells in mice

Radioprotective effect of irsogladine maleate, an anti-ulcer drug, on the intestinal crypt stem cell survival was studied in mice using a crypt microcolony assay. Irsogladine maleate was injected intraperitoneally immediately after irradiation and then, daily for three days. A successive administration of the drug following 10 Gy of irradiation increased the survival of intestinal stem cells with a clear dose-related trend. In order to estimate the D0, survival curves were determined for X-ray plus placebo and X-ray plus 10 mg/kg of irsogladine maleate. The D0, for X-ray plus the drug was 2.2 Gy while it was 1.9 Gy for X-ray plus placebo. These findings suggest that isogladine maleate can be applied for the alleviation of intestinal damages in heavily irradiated people by radiation accidents.

Gadolinium-DTPA enhancement of dural structures on MRI after surgery

Gadolinium-DTPA enhanced MRI was examined before and after surgery in 14 patients with particular attention to the enhancement of falx cerebri, tentorium cerebelli and dura mater. A marked enhancement was observed in 2 falx and 2 tentorium before surgery, whereas it was observed in 7 falx, 9 tentorium and 11 dura after surgery. Among 6 falx, 7 tentorium and 12 dura showing increased enhancement after surgery, 2 falx, 3 tentorium and 8 dura showed marked enhancement which was not observed before surgery. A small amount of subdural haemorrhage during surgery is known to heal as subdural neomembrane with capillaries. An increased enhancement of dural structures conceivably derives from the extravasation of Gd-DTPA through capillaries involved in the subdural neomembrane. In the postoperative MRI, the enhancement of dural structures should be taken into consideration.

Development of gap junctions between gastric surface mucous cells during cell maturation in rats

The development of gap junctions in rat gastric surface mucous cells during their maturation were examined by indirect immunofluorescence and freeze-fracture methods. Monoclonal antibody against liver gap junction protein stained in large spots along the intercellular junctions between mature gastric surface mucous cells. On the other hand, relatively small fluorescent spots were present over the immature surface mucous cells. The freeze-fracture method showed many large irregular gap junctions between mature surface mucous cells. In immature surface mucous cells, the gap junctions were less developed than those of mature cells, and small gap junctions were occasionally associated with tight junctional strands. Quantitatively, the gap junctions in mature cells were larger and more numerous than those in immature cells. These findings show that gap junctions develop during the maturation of surface mucous cells and suggest that the intercellular communication mediated by gap junctions between gastric surface mucous cells plays an important role in the regulation of cell differentiation and in tissue homeostasis.

Release kinetics of nicotinamide from fatty acid-nicotinamide equimolar complexes. II. Activation thermodynamic quantities

The rates of release of nicotinamide (NAA) from fatty acid (FA)-NAA complexes, FA-NAA, were determined at various temperatures, and the thermodynamic quantities for the release of NAA were estimated. The results were compared with the previous results obtained for FA-thiamine disulfide (TDS) complexes, (FA)6(TDS). The values of activation enthalpy (delta H ++) and activation entropy (delta S ++) for the release of NAA from FA-NAA were positive and negative, respectively, indicating that the release of NAA is disadvantageous from not only enthalpic but also entropic viewpoints. The plots of delta H++ against the carbon number (n) in the constituent FA showed a zig-zag line with an upward convex at an odd-numbered position and the plots of the absolute values of (-delta S++) showed a zig-zag line with a downward convex at an odd-numbered position, though the positive value of delta H++ increases and the negative value of delta S++ decreases with an increasing n for either even-numbered or odd-numbered FA. It was found that the release of NAA from FA-NAA formed with odd-numbered FA is more disadvantageous enthalpically but more advantageous entropically as compared with that from FA-NAA formed with even-numbered FA. This phenomenon was similar to that observed for (FA)6(TDS). Furthermore, it is suggested that FA-NAA is formed at least by van der Waals forces and hydrophobic interactions and that van der Waals forces are dominant for the formation of FA-NAA formed with odd-numbered FA and that hydrophobic interactions are dominant for the formation of FA-NAA formed with even-numbered FA.

Intercellular communication in cultured rabbit gastric epithelial cells

The effects of drugs related to cyclic AMP and a tumor promoter, phorbol ester, on intercellular communications via gap junctions were investigated by the Lucifer Yellow-transfer method in cultured rabbit gastric epithelial cells. Cells were in contact with each drug for 4 hr before the microinjection of the dye into a cell. Dye transfer capacity was significantly increased by dibutyryl cyclic AMP (10(-3) M), theophylline (10(-3) M), 3-isobutyl-1-methylxanthine (10(-4) M), forskolin (10(-6) M) and irsogladine (10(-4) M); and it was inhibited by 12-O-tetradecanoyl-phorbol-13-acetate (100 ng/ml). These results suggest that the intercellular communication between cultured rabbit gastric epithelial cells is upregulated by cyclic AMP.

4'-galactooligosaccharide affects sodium and potassium metabolism in rats

The effect of different levels (0, 10 and 20%) of O-beta-D-galactopyranosyl-(1-4)-O-beta-D-galactopyranosyl-(1-4)-D- glucose (4'-GL) on the bioavailability of sodium and potassium was studied in 18 male rats. Three 3-d metabolic balance studies were conducted during the 62-d feeding trial. These were between d 30 and 32 (first period), 45 and 47 (second period) and 60 and 62 (third period). Growth and food intake were not significantly different (P less than 0.05) between the control group and the 4'-GL-fed groups. In rats fed 10 and 20% 4'-GL diet, the fecal sodium excretion was significantly greater (P less than 0.05) in all three balance periods. Fecal potassium excretion was significantly greater (P less than 0.05) in the 10% 4'-GL-fed group in the second balance period and the 20% 4'-GL-fed group in all balance periods relative to the control group. Although not statistically significant, rats in the 4'-GL-fed groups exhibited a tendency for lower sodium retention and higher potassium retention compared with the control group. The cecal weight of rats in both 4'-GL-fed groups was significantly heavier (P less than 0.05) than that of the control group at the end of study. Sodium concentration in the cecum was significantly lower (P less than 0.05) in the 20% 4'-GL-fed group relative to the other groups.

Changes in cyclic AMP content of rat gastric mucosa induced by ulcerogenic stimuli--in relation to the antiulcer activity of irsogladine maleate

Changes in the cyclic AMP (cAMP) content of the gastric mucosa induced by ulcerogenic stimuli were investigated in rats. Ligation of the pylorus for 5 hr produced no glandular mucosal lesion, but increased the cAMP content in the fundus and antrum. Aspirin produced glandular mucosal lesions in the pylorus-ligated rats and caused an increase of the cAMP content in the fundus and a decrease in the antrum. Irsogladine maleate (IM), an antiulcer agent, inhibited both the changes in the cAMP content and the mucosal damage induced by aspirin. IM increased the cAMP content in both regions, especially the antrum, in normal rats. Dibutyryl cAMP (dbcAMP) given orally prevented the gastric mucosal lesions induced by aspirin without affecting gastric secretion. These results suggest that 1) the changes in the cAMP content of the fundus and antrum induced by aspirin may be associated with the formation of glandular mucosal damage, 2) the antiulcer activity of IM may be related to an increase of the cAMP content in mucous cells, and 3) dbcAMP given orally may penetrate into the surface mucous cells and activate defensive functions. Thus, cAMP in the mucous cells may protect the gastric mucosa.

Pharmacological properties of the new non-steroidal anti-inflammatory agent etodolac

The anti-inflammatory, analgesic, antipyretic and ulcerogenic activities of etodolac (CAS 41340-25-4), a new nonsteroidal anti-inflammatory agent, were compared with those of indometacin and other anti-inflammatory drugs in experimental animals. Etodolac had a remarkable anti-inflammatory effect in various experimental models: ultraviolet erythema, carrageenin-induced edema and swelling of adjuvant arthritis. In these models, the effective dose of etodolac was several fold that of indometacin. Etodolac inhibited prostaglandin E2 formation in a concentration-dependent manner, and its inhibitory potency was about 1/5 of that of indometacin. Etodolac also caused marked inhibition of granuloma formation and leucocyte functions such as chemotaxis, lysosomal enzyme release and active oxygen generation. These effects of etodolac were observed at similar doses of indometacin. Etodolac suppressed inflammatory pain but not non-inflammatory pain, and had an antipyretic effect but did not lower normal rectal temperature. Etodolac had no effect on delayed hypersensitivity reactions and was much less ulcerogenic than indometacin. These results indicate that etodolac is a low ulcerogenic anti-inflammatory agent with suppressing activities on leucocyte functions to the same extent as indometacin and prostaglandin biosynthesis.

Contrast enhancement of cystic portions in brain tumors on delayed image of gadolinium-DTPA-enhanced MR imaging

This report describes three patients whose cystic portions were filled with intravenously injected Gadolinium-DTPA. Four cystic portions showed contrast enhancement of the whole wall on early MR images and enhancement of the content on delayed MR images. Two cystic portions showed no enhancement of content. We speculate that the difference is based upon the composition of the cyst walls.

Microwave irradiation is effective in the rapid fixation of gastric mucosa for determination of the prostaglandin content

The gastric mucosal content of prostaglandin (PG) E2, 6-keto PGF1 alpha, and thromboxane (TX) B2 was determined by radioimmunoassay in unfed rats. The stomach was removed, and gastric mucosal specimens were prepared by microwave irradiation of the 1) intact stomach, 2) frozen stomach, 3) separated frozen glandular portion, 4) frozen gastric mucosa separated from the stomach wall, and 5) separation of frozen gastric mucosa with no microwave irradiation. Procedure 1 resulted in PGE2, TXB2, and 6-keto PGF1 alpha levels of 0.75, 2.33, and 3.04 ng/g tissue in the fundus, and 0.33, 1.92, and 1.76 ng/g tissue in the antrum, respectively. In procedures 2-4 these values were much higher, indicating that the PG content of the gastric mucosa is liable to be changed by various artificial procedures, such as freezing and surgical and mechanical handling. In procedure 5, values of PG contents were quite unreliable. These results suggest that microwave irradiation immediately after removal of the stomach may be the most reliable procedure for the accurate determination of the PG content of the gastric mucosa in vivo.

Effects of inhaled cadmium on breathing in the mouse

Effects of intranasally administered cadmium (3.67 micrograms Cd approximately 36.7 mg per mouse) on breathing were investigated in mice under pentobarbital anesthesia. Cd levels found in the respiratory tract were dependent on the amount administered. Cd mainly caused degeneration and desquamation of the bronchial epithelium and pulmonary congestion, while the carrier solvent had no effects. On the other hand, the carrier solvent decreased respiratory frequency and enhanced its amplitude. These effects were absent 24 h later. However, Cd strongly affected respiration; frequency and amplitude were decreased and recovery at 24 h was not complete at the higher concentrations. These effects by Cd on respiration were dependent on the concentration of administered Cd and the Cd level in lung. Therefore, these results suggest that intranasally administered Cd has inhibitory effects on mouse respiration, perhaps owing to its acute toxicity to pulmonary tissues.

Inhibition of H+,K+-ATPase by methyl(E)-2-(3,4-dimethoxystyryl)-benzimidazole-4-carboxylate (ALE-36)

ALE-36, as well as omeprazole and SCH 28080, markedly inhibited the [14C]aminopyrine (AP) accumulation induced by dibutyryl cyclic AMP (dbcAMP) and H+,K+-ATPase activity in a concentration-dependent manner. The inhibitory effect of omeprazole on the dbcAMP-induced [14C]AP accumulation was reversed by treatment with beta-mercaptoethanol, but those of ALE-36 and SCH 28080 were not. ALE-36 and SCH 28080 did not inhibit dog renal Na+,K+-ATPase activity, while omeprazole and ouabain did inhibit this enzyme activity. These results suggest that the inhibitory action of ALE-36 on acid secretion is due to the specific inhibition of gastric H+,K+-ATPase, the manner being different from in the case of omeprazole.

Effects of extracellular calcium and sodium on cadmium uptake in guinea-pig and rabbit aorta

1. Effects of Na+ and Ca2+ on Cd2+ uptake in the guinea-pig and rabbit aorta were investigated. 2. The Cd2+ fraction can be divided with EDTA and Zn2+. The EDTA fraction may be intracellular fraction and the Zn2+ fraction may be loosely bound to surface membrane. 3. In Na+ deficient solution the Zn2+ fraction was markedly increased and the EDTA fraction also increased while the external Ca2+ concentrations scarcely affect the Cd2+ contents in both fractions. 4. Cd2+ did not affect the cellular Na+ and K+ contents. 5. These results suggest that Na+ strongly relates with these fractions but Na+ pump does not contribute to these phenomena.

Effects of ALE-36 on gastric secretion, and gastric and duodenal ulcers induced in rats

We examined the antisecretory and anti-ulcer effects of ALE-36 in rats. ALE-36 (3-30 mg/kg) dose-dependently inhibited gastric acid secretion in pylorus-ligated rats. However, the agent apparently increased the volume of gastric juice, and the Na+ and Cl- ion outputs. These changes were almost completely prevented by pretreatment with indomethacin, suggesting that endogenous prostaglandins in the gastric mucosa mediated the changes. Pretreatment with ALE-36 (3-30 mg/kg) inhibited the development of stress-, aspirin-, and indomethacin-induced gastric lesions, and mepirizole-induced duodenal ulcers. Repeated administration of ALE-36 significantly accelerated the healing of gastric ulcers induced by thermocautery.

Effects of zinc and EDTA on tissue cadmium in various smooth muscles in rabbit and guinea-pig

1. The effects of zinc (Zn2+) and ethylenediaminetetra-acetic acid (EDTA) on tissue cadmium (Cd2+) were investigated in the smooth muscles of rabbit trachea, taenia coli, aorta and guinea-pig taenia coli. 2. After an Cd uptake in high-K2+ solution, samples were rinsed with cold high-K2+, cold Zn2+ or cold EDTA solution without Cd2+ and the results were quantitatively different from each other. 3. Concentration-response curves were obtained with each treatment of cold solution. 4. It is suggested that tissue Cd2+ can be divided into 3 fractions in the surface membrane and there is another fraction in cellular space.

Interacting effects of zinc and cadmium on the cadmium distribution in the mouse

Effects of zinc (Zn) on cadmium (Cd) distribution in the mouse body were investigated after intranasal administration. The amounts of Cd (2 x 10(-6) M/0.02 ml) reaching respiratory organs increased as the ip dose of pentobarbital increased. Administration of Zn with Cd (2 x 10(-6) M Zn + 2 x 10(-6) M Cd /0.02 ml) further increased the Cd amounts reaching respiratory organs and increased mouse mortality. A single administration of Cd increased Cd levels in blood, liver, kidney and respiratory organs. High levels of Cd were maintained for at least 90 days in these organs after single administrations of Cd. The administration of Cd plus Zn further increased the Cd content in these organs during 0-60 min after administration. However, simultaneous administration of Zn with Cd inhibited prolonged Cd accumulation in kidney and liver. These results suggest that intranasally administered Zn (2 x 10(-6) M) has dual effects on Cd movement. Zn further increases the Cd levels in the lung and mouse mortality increases. On the contrary, Zn inhibits prolonged Cd accumulation in mice and decreases the chronic toxicity in mice that survive the acute phase.

[Protective effect of dicloguamine maleate (MN-1695) on HCl-induced gastric mucosal damage in rats--histologic studies]

Effect of MN-1695, a new cytoprotective antiulcer agent, on 0.2 N HCl-induced gastric surface epithelial cell damage was investigated by optical and transmission electron microscopy in rats. Tissue examination after five minutes exposure to 0.2 N HCl showed extensive damage of the surface epithelial cells: dilatation of intercellular spaces including marked edema of lamina propria. It was found that MN-1695 (3 mg/kg) pretreatment prevented such 0.2 N HCl-induced damage of the surface epithelial cells, and it reduced the percentage of damaged mucosa, but not significantly.

Effect of 2,4-diamino-6-(2,5-dichlorophenyl)-s-triazine maleate (MN-1695) on gastric ulcers and gastric secretion in experimental animals

The effect of 2,4-diamino-6-(2,5-dichlorophenyl)-s-triazine maleate (MN-1695) on various experimental gastric ulcers and gastric secretion in experimental animals was compared with that of cimetidine and cetraxate. MN-1695 significantly inhibited the formation of Shay, stress-induced, indomethacin-induced, and histamine-induced ulcers and significantly accelerated the healing of acetic acid-induced gastric ulcers. MN-1695 was much more effective in suppressing stress- and acetic acid-induced ulcers than indomethacin-induced, histamine-induced or Shay ulcers. Cimetidine was effective in preventing stress- and acetic acid-induced ulcers but had no significant effect on Shay, indomethacin-induced and histamine-induced ulcers. Cetraxate was effective in preventing only stress-induced ulcers and had almost no effect on other experimental ulcers. MN-1695 inhibited secretion of gastric juice, acid and pepsin in Shay rats, but had no influence on basal and secretagogue-stimulated acid secretion in the perfused stomach of urethanized rats. These findings suggest that MN-1695 is a new type of anti-ulcer agent.

Effects of vanadate on mechanical and electrical activities in guinea-pig taenia coli

Effects of vanadate (NH4VO3 and Na3 VO4: VAN) on electrical and mechanical activities and cellular Na content in guinea-pig taenia coli were examined. VAN (1-5 X 10(-4) M) transiently increased membrane potential and decreased muscle tension. Several minutes later, muscle tension increased following membrane depolarization and increase in spike frequency. The initial relaxing effect of VAN was not affected by ouabain, phentolamine and propranolol, and the contractile effect was not affected by atropine and tetrodotoxin. The VAN-induced contraction was dependent on external Ca and was abolished by verapamil. VAN also induced a contraction in depolarized taenia, which was augmented when external Ca concentration was lowered. VAN (10(-3) M) did not change cellular Na content. It is suggested that VAN-induced relaxation is due to the decrease in membrane electrical activities whereas contraction is attributable to the increased electrical activities followed by Ca influx and also to nonelectrical mechanism followed by mobilization of cellular Ca. These changes do not seem to be related to Na pump activity.

Effect of 2,4-diamino-6-(2,5-dichlorophenyl)-s-triazine maleate (MN-1695) on gastric mucosal blood flow in dogs

The effect of 2,4-diamino-6-(2,5-dichlorophenyl)-s-triazine maleate (MN-1695) on gastric mucosal blood flow ( GMBF ) and on the changes of GMBF induced by catecholamines, tetragastrin, histamine and indomethacin were investigated in anesthetized dogs. MN-1695 at doses up to 1 mumol/kg i.v. showed only a slight but prolonged increase of GMBF . MN-1695 tended to inhibit the decreases of GMBF induced by norepinephrine and the increase of GMBF induced by tetragastrin. The later phase of decreased GMBF induced by histamine was suppressed by MN-1695. However, MN-1695 had almost no effect on the increase of GMBF induced by epinephrine. MN-1695 produced a marked increase of antral mucosal blood flow which was reduced by pretreatment with indomethacin. Systemic blood pressure, respiration and the pressor responses induced by catecholamines and gastric secretagogues were not affected by MN-1695. These results suggest that MN-1695 may possess selective effects on the gastric mucosal microcirculation and that suppressive effects of MN-1695 on the GMBF decrease induced by ulcerogenic stimuli may be responsible for its anti-ulcer activities in various types of experimental gastric ulcers.

High K-induced contractions in rabbit and monkey tracheal smooth muscle

High K-induced contractions in rabbit and monkey tracheal smooth muscle were characterized. A substituted 60 mM K, 94.1 mM Na solution produced a sustained contraction in both preparations. The 60 mM K-induced contraction in rabbit trachea was inhibited by Ca removal, verapamil, glucose-removal and hypoxia but not by sodium nitroprusside. The 60 mM K-induced contraction in monkey trachea was inhibited by Ca removal, verapamil, sodium nitroprusside and hypoxia but not by glucose-removal. In rabbit trachea a substituted 154.1 mM K, Na deficient solution induced a rapid rise in tension followed by a gradual decrease. Wet weight of rabbit trachea increased in the 154.1 mM K solution. Both the decrease in the developed tension and the increase in the wet weight were prevented by the hyperosmotic addition of sucrose (50-100 mM). The decrease in the developed tension was also partially antagonized by the addition of pyruvate or oxalacetate. In monkey trachea, the sustained contraction induced by the 154.1 mM K solution showed very slow decrease following the increase in the wet weight of the tissue. The decrease in muscle tension was prevented by the addition of hyperosmotic sucrose. These results suggest that, in rabbit tracheal smooth muscle, the decrease in the developed tension in isosmotically substituted high K, Na deficient solution may be attributable mainly to the swelling of muscle cells and partly to the inhibition of glucose utilization resulting from Na deficiency. In contrast, the contraction in monkey trachea seems to be inhibited, although slightly, by the swelling of the cells.

Inhibitory effects of vanadate on the contractile responses in vascular smooth muscle

The effects of vanadate (Na3VO4) on the contractions induced by high concentrations of K, histamine and norepinephrine in isolated guinea-pig aorta were investigated. Vanadate (10(-3) M) relaxed the high K contraction only when the external K concentration was above 85.4 mM. Vanadate showed no inhibitory action on the contraction induced by either Na-containing 45.4 mM K solution or Na-poor 45.4 mM K solution. Ouabain (2 X 10(-5) M) had no inhibitory effects on the contractions induced by these high K solutions. Vanadate failed to relax the contraction induced by histamine or norepinephrine in normal (5.4 mM) medium, while it inhibited the contraction in the presence of 142.2 mM K. Ouabain also did not inhibit the histamine- or norepinephrine-induced contraction in either normal or high K solution. These results suggest that the inhibitory actions of vanadate are not due to an inhibition of Na pump and that these effects depend on the presence of a high concentration of external K ions.

Dual actions of vanadate on high K-induced contraction in guinea-pig taenia coli

Effects of vanadate (NH4VO3: VAN) on tension development, membrane potential and cellular Na content were investigated in guinea-pig taenia coli depolarized by 62.7 mM KCl solution. VAN (10(-4) - 10(-3) M) caused a transient increase in the K developed tension followed by a relaxation. The VAN-induced contraction was observed even in a low Ca (0.13 mM) solution but was inhibited by the removal of external Ca. After the addition of verapamil (5 x 10(-8), 10(-7) M). VAN still produced a contraction. Further, the VAN-induced contraction was observed in 142.2 mM KCl (Na 11.9 mM) solution containing ouabain (10(-4) M). On the other hand, the effect of VAN to relax the K-induced contraction was dependent on the concentration of VAN. In low Na (choline-substituted) solution, the VAN-induced relaxation was decreased. VAN increased cellular Na content of the depolarized muscle, and a correlation was obtained between the cellular Na accumulation and the relaxation. These results suggest that the relaxation is mainly attributable to the accumulation of Na following the inhibition of the Na pump, while the contraction is independent of the inhibition of the Na pump and less sensitive to the external Ca than the K-induced process.