Effect of Aronia melanocarpa fruit juice on indomethacin-induced gastric mucosal damage and oxidative stress in rats.

Aronia melanocarpa fruits are rich in phenolic substances-mainly flavonoids from the anthocyanin subclass. The anthocyanins are water-soluble plant pigments with antioxidant, anti-inflammatory, antimicrobial, hepatoprotective, gastroprotective and other activities. We studied the effect of A. melanocarpa fruit juice (AMFJ) on indomethacin-induced gastric mucosal damage in rats and its possible relation to the oxidative status. AMFJ (5, 10 and 20 ml kg(-1)) was applied orally as a pretreatment 1 h before the subcutaneous administration of indomethacin (30 mg kg(-1)). Gastric ulcer formation was estimated morphometrically and histopathologically 4h after the indomethacin administration. Malondialdehyde (MDA) in rat plasma and gastric mucosa and also reduced glutathione (GSH) and oxidized glutathione (GSSG) in gastric mucosa were determined and used as biochemical markers of the oxidative status. AMFJ-pretreatment diminished the number and area of indomethacin-induced gastric lesions. Histopathological examination of rat stomachs demonstrated that AMFJ induced an increase in gastric mucus production and a reduction of the depth and severity of indomethacin-induced mucosal lesions. AMFJ dose-dependently reduced the elevated indomethacin plasma and gastric MDA levels and at the doses of 10 and 20 ml kg(-1) they were not significantly different from the control values. Neither indomethacin-treatment, nor AMFJ-pretreatment had a significant influence on GSH and GSSG gastric mucosal levels. These results demonstrated that indomethacin-induced gastric mucosal damage was accompanied by the development of oxidative stress, evidenced by the accumulation of MDA. AMFJ-pretreatment decreased the gastric lesions caused by indomethacin. It could be suggested that this effect of AMFJ was probably due to the increased mucus production and interference with oxidative stress development as evidenced by the decreased plasma and gastric mucosal MDA.

Effects of 2,5-di-t-butyl-1,4-benzohydroquinone (BHQ) on rat aorta smooth muscle.

To characterise the pharmacological activity of 2,5-di-t-butyl-1,4-benzohydroquinone (BHQ) on vascular smooth muscle, the different effects of BHQ on rat aorta were investigated under several experimental conditions. In aortic rings at rest or depolarised with 80 mM K+ in the presence of 1 microM nifedipine, BHQ evoked a slow tonic contraction which was antagonised by 1 mM Ni2+. Depolarised rings contracted in response to addition of 1 mM Ca2+, with an EC50 value of 32.4+/-1.0 mM for K+. At 20 mM K+, Ca2+-induced contraction was enhanced by BHQ. This effect was antagonised by 1 mM Ni2+, but not by 1 microM nifedipine. By contrast, at 40, 80 and 128 mM K+, BHQ antagonised Ca2+-induced contraction. This effect was partially reversed by 1 microM methyl-1,4-dihydro-2,6-dimethyl-3-nitro-4-(2-trifluoromethylphenyl)-pyri dine-5-carboxylate (Bay K 8644) or by increasing extracellular Ca2+ concentration. In the presence of nifedipine and Ni2+, depolarised rings (80 mM K+) contracted in response to addition of 1 microM phenylephrine; this response was fast and then slowly decreased. When the preparations were preincubated with BHQ, the phenylephrine-induced contraction was transient and antagonised in a concentration-dependent manner by BHQ. These results indicate that the myotonic effect of BHQ on rat aortic rings depends on activation of Ca2+ influx via a Ni2+-sensitive pathway, whereas its myolytic activity is due either to antagonism of Ca2+ entry via L-type Ca2+ channels or depletion of intracellular Ca2+ stores.

On the mechanisms of the antispasmodic action of some hindered phenols in rat aorta rings.

The antispasmodic effects of 3-t-butyl-4-hydroxyanisole (BHA) and some structurally related compounds were investigated in endothelium-intact rat aorta rings. Nordihydroguaieretic acid (NDGA), BHA, 3,5-di-t-butyl-4-hydroxyanisole (DTBHA), 2,6-di-isopropyl phenol (propofol) and 2,2'-dihydroxy-3,3'-di-t-butyl-5, 5'-dimethoxydiphenyl (DIBHA) did not cause relaxation when added at the plateau of phenylephrine-evoked contraction, nor did they affect the concentration-relaxation curve for acetylcholine in precontracted rings. In rings depolarised with physiological salt solution (PSS) containing 40 mM K(+), NDGA, BHA, DTBHA, 2, 5-di-t-butyl-1,4-benzohydroquinone (BHQ), propofol and nifedipine, but not DIBHA, inhibited the contraction induced by cumulative addition of Ca(2+) (0.05-10 mM) in a concentration-dependent manner; this inhibition was inversely related to the Ca(2+) concentration. In 40 mM K(+) PSS, 25 nM nifedipine blocked the 1 mM Ca(2+)-induced contraction, whereas 50 microM DTBHA, NDGA, BHA, BHQ and propofol significantly antagonised it by 84.4%, 73.0%, 52.8%, 45.6% and 35.7%, respectively. In the presence of 1 microM methyl-1,4-dihydro-2, 6-dimethyl-3-nitro-4-(2-trifluoromethylphenyl)-pyridine-5-carboxylate (Bay K 8644), the response to Ca(2+) did not differ from control values with nifedipine and BHQ, was partially restored with DTBHA and NDGA, and was not affected with BHA and propofol. Nifedipine markedly inhibited (85.2%) the Ba(2+)-induced contraction and this effect was totally reversed by Bay K 8644. BHA and DTBHA showed antispasmodic activity (45.3% and 43.1%, respectively) which was partly reversed by Bay K 8644. In contrast, Bay K 8644 did not affect the inhibition exerted by BHQ, NDGA and propofol (69.5%, 53. 3% and 46.1%, respectively). Nifedipine, BHA, DTBHA, propofol and NDGA inhibited the contractile response to 1 mM Ca(2+) of aorta rings depolarised with 40 or 80 mM K(+) PSS to a similar extent. Cromakalim inhibited the Ca(2+)-evoked contraction only in 30 mM K(+) PSS and BHQ only in 80 mM K(+) PSS. DIBHA had no effect on this model. Cromakalim, but not BHA, stimulated 86Rb(+) efflux from ring preparations. In 80 mM K(+) PSS containing 1 microM nifedipine, only papaverine affected the phenylephrine-induced contraction. Moreover, when the rings were preincubated with 1 mM Ni(2+), the response to phenylephrine in the presence of BHQ was significantly reduced. In conclusion, we propose that BHA may non-specifically inhibit Ca(2+) influx at the plasmalemma level rather than affect the function of K(+) channels, Ca(2+) release from intracellular stores or endothelium-dependent relaxation.

Mechanical response to electrical field stimulation of rat, guinea-pig, monkey and human detrusor muscle: a comparative study.

The aim of the present investigation was to compare mechanical responses to electrical field stimulation (EFS), as well as cholinergic and non-adrenergic, noncholinergic (NANC) neurotransmission in guinea-pig, rat, monkey and human detrusor muscle strips. Responses to EFS (0.05, 0.5 and 1 ms pulse duration, 50 V, 1-15 Hz) of guinea-pig, rat, monkey and human detrusor muscle strips were recorded isometrically before and after blockade of muscarinic receptors and/or P2-purinoreceptors, as well as after desensitisation of P2-purinoceptors or blockade of the nerve impulse propagation. Single pulses of 0.05 ms duration elicited responses, in either guinea-pig or rat detrusor strips, which were abolished by tetrodotoxin (TTX), thus suggesting their neurogenic nature. In monkey and human detrusor strips, however, the same single pulses were not sufficient to generate contractile responses. The response of either rat or guinea-pig strips to single pulses of 0.5 ms and 1 ms duration was mainly myogenic in nature. While in rat and guinea-pig strips the neurogenic response was only partly reduced in the presence of atropine, in monkey and human strips it was abolished. In the presence of atropine, while suramin only partially reduced the EFS response either in rat or guinea-pig detrusor strips, a complete alpha,beta-methyleneATP-sensitive response was evident in guinea-pig detrusor strips. This suggests the involvement of other transmitter(s) beyond ATP in the NANC response of rat detrusor strips.

Gastroprotective effect of MX1 (a novel salt of the active metabolite of roxatidine with a complex of bismuth and citric acid) against stress ulcers in rats.

We have studied the effect of the newly synthesized agent MX1, a salt of the active metabolite of the H2-blocker roxatidine with a complex of bismuth and citric acid (N-[3-(3-(1-piperidinylmethyl)phenoxy)propyl]-hydroxyacetamide+ ++ -2-hydroxypropane-1,2,3-tricarboxilate-bismuth(3+) complex), against restraint stress ulcers in rats (24 h immobilization). The effects of MX1 (12.5, 50, 125, 184 and 250 mg kg-1) were compared with the effects of equimolar doses of roxatidine (6.5, 25, 70, 100 and 140 mg kg-1) and bismuth subcitrate (6.5, 25, 70, 100 and 140 mg kg-1). The results show that MX1-pre-treatment, at all the doses used, significantly reduces the mean number and size of ulcers. Even at the lowest dose the number of ulcers was reduced by 64.3% and the size of the ulcer by 55.9%. Roxatidine (25, 70, 100 and 140 mg kg-1) dose-dependently reduces ulcer size and number by 24.6, 55.6, 85.3 and 89.0% and by (+7.2), 14.3, 57.1 and 67.9%, respectively. Bismuth subcitrate significantly reduces ulcer size and number only at the highest dose employed (-28.5 and -44.8%, respectively). The morphometric results have been confirmed histomorphologically. The results suggest that MX1 has a gastroprotective effect against stress-induced ulcers which is similar to that of the parent compound and more pronounced than that of bismuth subcitrate.

Gastric mucosal lesions in influenza virus infected mice: role of gastric lipid peroxidation.

The present study provides direct experimental proof that the combination of influenza virus infection A/Aichi/2/68 (H3N3) with different models of oxidative stress, such as immobilization, cold and cold-restraint, is associated with graduated oxidative disturbances in the stomach of mice, despite the absence of virus replication and inflammation in this tissue. It was found that experimental influenza virus infection is accompanied with significant changes in gastric mucosal integrity, as well as an increase in the products of lipid peroxidation in the stomachs of mice. Preliminary exposure of mice to immobilization stress and subsequent inoculation of influenza virus did not significantly influence gastric ulceration or lipid peroxidation compared with infected mice. Cold stress resulted in a significant decrease in the index of stomach ulceration and did not influence the fluorescent products of lipid peroxidation and MDA compared with infected animals. The simultaneous application of cold-restraint stress and influenza virus infection provoked synergism in the activity of all factors on the parameters under investigation. Ulceration increased approximately two-fold, as did the amount of fluorescent products of lipid peroxidation and MDA, compared with influenza virus-infected and non-stressed animals.

Effect of roxatidine bismuth citrate (MX1) against acetylsalicylic acid- and indomethacin-induced gastric mucosal damage in rats.

We have studied the effect of the newly synthesized agent, roxatidine bismuth citrate (N-[3-(3-(1-piperidinyl-methyl)phenoxy)propyl]-hydroxyacetamide-2- hydroxypropane-1,2,3-tricarboxylate-bismuth(3+) complex), code name MX1, against acetylsalicylic acid (ASA)- and indomethacin-induced gastric mucosal damage in rats. Effects of MX1 (12.5, 50, 125, 184, 250 mg/kg) were compared to the effects of equimolar doses of roxatidine and bismuth subcitrate. Effect of MX1 (10(-6) M) on mucin biosynthesis measured by [3H] glucosamine incorporation in rat gastric corpus has been determined. MX1-pretreatment dose-dependently decreased the mean ulcer number and length in all doses used in an extent similar to that of roxatidine and more pronounced in comparison with bismuth subcitrate. The morphometrical results have been confirmed histomorphologically. The biosynthesis of mucin was found to be significantly enhanced after MX1 addition. The results of the present study suggest that MX1 has a gastroprotective effect against ASA- and indomethacin-induced ulcers which might be due both to its H2-blocking and mucus-stimulating activity.

Epidemiological study of the frequency of prescribing antiepileptic drugs.

This epidemiological study reviewed the frequency of prescribing antiepileptic drugs for the period 1982 to 1991 in four regions of Bulgaria. The study included 8,340 outpatients with epilepsy. The therapeutic approaches to primary generalized, focal, and secondary types of epilepsy were evaluated. The drug of preference in all types of epilepsy was found to be phenobarbital (26.3 to 37.8%), followed by carbamazepine (14.0 to 29.8%), bellonal, sacerno, phenytoin, etc. Valproate was prescribed only in a few cases (0 to 2.1%). Combinations of phenobarbital anc carbamazepine prevailed in the therapeutic approach to epilepsy. The share of polytherapy in the treatment of epilepsy tended to decrease in favour of monotherapy. The data on the antiepileptic drug utilization given in the present study are calculated in the internationally accepted unit, a daily defined dose.

[The effect of the calcium channel blockers cinnarizine and flunarizine on the duration of hexobarbital-induced sleep i rats]. / Vliianie blokatorov kal'tsievykh kanalov tsinnarizina i flunarizina na prodolzhitel'nost' geksobarbitalovogo sna u krys.

The effect of the calcium channel blockers cinnarizine (20 mg/kg) and flunarizine (10 mg/kg) on hexobarbital sleeping time in rats has been studied. We have found that cinnarizine when applied intraperitoneally once 1 h or 4 h before hexobarbital and repeatedly for 5 days once daily prolongs sleeping time significantly. When cinnarizine has been introduced simultaneously with phenobarbital (60 mg/kg) for 5 days once daily the sleeping time that was expected to be shortened by phenobarbital only has been obtained to return to control values. Flunarizine has not been found to affect sleeping time significantly either alone or in the presence of phenobarbital. Latencies have not been altered by any of both agents.

Gastric histamine content and ulcer formation in rats with ethanol-induced injury. Effects of cinnarizine and flunarizine.

The effects of the calcium antagonists cinnarizine and flunarizine on gastric histamine content and ulcer formation in rats with ethanol-induced injury were studied. Gastric ulcers were inflicted by oral application of 50% or 100% ethanol solution. Cinnarizine (20 mg/kg), flunarizine (10 mg/kg) and cimetidine (100 mg/kg) were administered orally 1 h before ethanol. Histamine was assayed fluorometrically. No effect of the tested drugs on 50% ethanol-induced gastric damage was observed. Cinnarizine and flunarizine inhibited 100% ethanol-induced lesion formation by 71% (p < 0.01) and 20% (p > 0.05), respectively. The inhibition exerted by cimetidine was 54% (p < 0.05). Gastric histamine content was not affected by 50% ethanol, while 100% ethanol decreased it two-fold. None of the tested drugs induced significant changes in gastric histamine levels. No correlation was obtained between the ulceroprotective effect of the used calcium antagonists and the gastric histamine content in ethanol-induced injury.

Effects of carnitine and its derivatives on gastric acid secretion in rats.

Carnitine is a natural substance that acts as a carrier of fatty-acids across the inner mitochondrial membrane for subsequent beta-oxidation. Acetyl-L-carnitine is the acetyl derivative of L-carnitine that has been shown to possess a slight cholinomimetic activity. Its success in sports medicine is dependent on the fact that it is able to stimulate the central nervous system functions. This study aims to investigate the effects of L-carnitine (LC) and its derivatives-acetyl-L-carnitine (ALC) and propionyl-L-carnitine (PLC)-on gastric acid secretion in rats. A concentration-dependent relationship with both ALC or PLC was observed in experiments in vitro using a rat isolated stomach. The addition of atropine to the perfusion bath only partially antagonized the effects of the two compounds. Stimulation of gastric acid secretion in a dose-dependent manner was also found when the tested compounds were administered i.v. to anaesthetized rats. To elucidate the mechanism of the gastric secretory response, assay for acetylcholine esterase activity using acetylthiocholine as substrate, was performed. It was found that ALC and PLC inhibited acetylcholine esterase, however, the IC50 for both compounds was about four times of magnitude greater than that of eserine. As the increase of the gastric acid secretion promoted by carnitines was blocked only partially by atropine both in vitro and in vivo, whilst it was completely abolished by experimental degeneration of the sympathetic neurons or by blockade of the postsynaptic sympathetic receptors, it is suggested that the effect of carnitines is determined by cholinergic and partly by adrenergic mechanisms.

Gastroprotective effect of propacetamol against cold/restraint stress ulcers in rats.

BACKGROUND: Comparative evaluation of propacetamol and morphine on the cold restraint stress ulcers in rats. METHODS: The present study compared the effects of propacetamol hydrochloride (250 and 500 mg.kg-1 i.p.) and morphine hydrochloride (10 mg.kg-1 i.p.) against gastric mucosal damage induced by cold/restraint stress (4 degrees C for 3 h) in rats. Morphometrical and histomorphological studies were carried out. Mean ulcer number and length were calculated. RESULTS: The results show that propacetamol in the lower dose tested decreases the ulcer number and length by 56.4% (p > 0.05) and by 68.94% (p < 0.01). After propacetamol 500 mg.kg-1 the ulcer number and length were found significantly decreased by 74.83% and 83.5%. Marked decrease was found in morphine-pretreated group (-77.03% and -85.09%). The morphometrical results have been confirmed histomorphologically. CONCLUSIONS: It might be concluded that morphine (10 mg.kg-1) and propacetamol (500 mg.kg-1) are equipotent in their ability to prevent the stress ulceration in rats.

Functional characterization and expression of PBR in rat gastric mucosa: stimulation of chloride secretion by PBR ligands.

Previous studies have demonstrated that gastric mucosa contained high levels of the polypeptide diazepam binding inhibitor, the endogenous ligand of the peripheral-type benzodiazepine receptor (PBR). However, the expression and function of this receptor protein in these tissues have not been investigated. Immunohistochemistry identified an intense PBR immunoreactivity in the mucous and parietal cells of rat gastric fundus and in the mucous cells of antrum. Immunoelectron microscopy revealed the mitochondrial localization of PBR in these cells. Binding of isoquinoline PK 11195 and benzodiazepine Ro5-4864 to gastric membranes showed that fundus had more PBR-binding sites than antrum, displaying higher affinity for PK 11195 than Ro5-4864. In a Ussing chamber, PK 11195 and Ro5-4864 increased short-circuit current (I(sc)) in fundic and antral mucosa in a concentration-dependent manner in the presence of GABA(A) and central benzodiazepine receptor (CBR) blockers. This increase in I(sc) was abolished after external Cl(-) substitution and was sensitive to chloride channels or transporter inhibitors. PK 11195-induced chloride secretion was also 1) sensitive to verapamil and extracellular calcium depletion, 2) blocked by thapsigargin and intracellular calcium depletion, and 3) abolished by the mitochondrial pore transition complex inhibitor cyclosporine A. PK 11195 had no direct effect on H(+) secretion, indicating that it stimulates a component of Cl(-) secretion independent of acid secretion in fundic mucosa. These data demonstrate that mucous and parietal cells of the gastric mucosa express mitochondrial PBR functionally coupled to Ca(2+)-dependent Cl(-) secretion, possibly involved in the gastric mucosa protection.

Effects of paracetamol and propacetamol on gastric mucosal damage and gastric lipid peroxidation caused by acetylsalicylic acid (ASA) in rats.

We have studied the effect of paracetamol and its pro-drug propacetamol on gastric mucosal damage induced by acetylsalicylic acid (ASA) and its possible relation to changes in gastric lipid peroxidation status in rats. Paracetamol or propacetamol were administered intragastrically 1h before ASA (300 mg kg(-1)) in the following equivalent doses: 62.5, 125.0 and 250.0 mg kg(-1) or 125.0, 250.0 and 500.0 mg kg(-1), respectively. The effects of the tested agents were compared to that of prostaglandin E2 (PGE2) 15, 30 and 60 mg kg(-1). Gastric ulcer formation was estimated morphometrically 4h after ASA administration. Malondialdehyde (MDA), glutathione (reduced, GSH, and oxidized, GSSG) and uric acid (UA) were determined in gastric mucosa and blood plasma and used as biochemical markers of the oxidative status. The results showed that paracetamol (250, 125, 62.5 mg kg(-1)) and propacetamol (500, 250, 125 mg kg(-1)) diminished the area of ASA-induced gastric lesions. The effect of propacetamol was more pronounced than that of paracetamol and similar to that of PGE2. Gastric MDA increased 3-fold in the ASA-group. The tested agents reduced it by a range of 30-70%. In all pretreated groups gastric glutathione and UA levels were found higher than that of control group and lower than that of ASA-group. Paracetamol and propacetamol, as well as PGE2, diminished the lipid peroxidation in plasma to a lesser extent than in gastric mucosa, but maintained elevated levels of the selective plasma antioxidant UA. These results show that the ASA-induced gastric mucosal damage is accompanied by the development of oxidative stress, evidenced by the accumulation of MDA, and concomitant initial activation of cell antioxidant defences. As paracetamol and propacetamol tend to decrease gastric lesions caused by ASA and alter gastric mucosal MDA, glutathione and UA values in a favorable manner, it could be suggested that their effects on the gastric mucosa could be related to interference with oxidative stress development.