Platelet activating factor potentiates rat paw oedema induced by different phlogogen agents

Carrageenin oedema is enhanced by the simultaneous injection in the rat paw of platelet activating factor (PAF). The enhancement of carrageenin oedema is observed throughout the time course of the experiments. This enhancement is also present when the oedema-producing agent is dextran, cellulose sulphate, histamine, 5-hydroxytryptamine, bradykinin or prostaglandin E2. Both verapamil and BN 52021 abolished the enhancement induced by PAF without modifying significantly carrageenin oedema. In essential fatty acid deficient (EFAD) rats depleted of kininogen and amines, carrageenin oedema is not modified by PAF. These findings suggest that PAF interacts with other inflammatory mediators regulating the formation of oedema induced by irritants injected locally.

Essential fatty acid-deficient diet modifies PAF levels in stomach and duodenum of endotoxin-treated rats

Platelet-activating factor (PAF) is thought to play an important role in pathogenesis of endotoxin shock. Here, using essential fatty acid deficient (EFAD) rats, we have evaluated changes in mean arterial blood pressure, PAF levels and damage in both stomach and duodenum following intravenous administration of endotoxin (LPS). In EFAD rats the second phase of LPS-induced hypotension was strongly reduced. Similarly, PAF levels in stomach and duodenum of EFAD rats were also reduced and correlated to the diminished damage. Our study confirms a direct involvement of PAF in LPS-induced gastrointestinal damage.

Nitric oxide and castor oil-induced diarrhea

The effect of NG-nitro-L-arginine methyl ester (L-NAME) on castor oil-induced diarrhea was studied in control rats and those treated with isosorbide dinitrate or isosorbide-5-mononitrate. Castor oil (2 ml) produced diarrhea that lasted at least 8 h. Pretreatment of the rats with L-NAME (1-25 mg/kg i.p.) 15 min before castor oil did not block the castor oil-induced diarrhea beyond 3 h after challenge but delayed its appearance (P < .05-.001). However, diarrhea was inhibited (P < .01-.001) during the entire 8 h if rats were treated twice with L-NAME (25 mg/kg) (15 min before and 3 h after castor oil). These findings suggest that L-NAME, once administered, loses its activity 3 h after its administration. The nitric oxide synthase substrate, L-arginine (150-600 mg/kg), reversed (P < .05-.01) the inhibitory effect of L-NAME on diarrhea induced by castor oil. This effect is enantiomer-specific because D-arginine (900 mg/kg) was without an effect. These results suggest that castor oil-induced diarrhea in rats involves the L-arginine nitric oxide pathway. This is further supported by the effect of isosorbide dinitrate (0.6-120 mg/kg) and isosorbide-5-mononitrate (0.6-120 mg/kg). When administered to castor oil-treated rats, these two nitric oxide-generating agents prevented in a dose-dependent fashion (P < .01-.001) the inhibitory effect of L-NAME (25 mg/kg).

Inhibition of intestinal motility and secretion by flavonoids in mice and rats: structure-activity relationships

Intraperitoneal administration of some flavonoids (apigenin, flavone, kaempferol, morin, myricetin, naringin and rutin; 12.5-50 mg kg-1) significantly (P < 0.05-0.01) reduced small (28-69%) and large (83-134%) intestinal transit in mice. Other flavonoids (naringenin, silibinin, silymarin and taxifolin, 100-200 mg kg-1) reduced (23-41%; P < 0.05-0.01) intestinal transit at doses of 100-200 mg kg-1 while hesperitin, catechin and phloridzin (up to 200 mg kg-1) had no effect. This effect was antagonized by yohimbine (87-96%) and phentolamine (87-91%) but not by prazosin, propranolol, atropine, hexamethonium, mepyramine, cyproheptadine and naloxone. Yohimbine (92-96%) also antagonized the inhibitory effect of flavonols (12.5-50 mg kg-1) (P < 0.05-0.01) on intraluminal accumulation of fluid and diarrhoea induced by castor oil. By contrast, verapamil potentiated the flavonol effect. It is suggested that these effects, influenced by the structure of the molecules, are mediated by alpha 2-adrenergic receptors and calcium.

Inhibitors of nitric oxide synthase enhance rat ileum contractions induced by ricinoleic acid in vitro

The effects of NG-nitro-L-arginine methyl ester (L-NAME) and NG-monomethyl-L-arginine (L-NMMA), inhibitors of nitric oxide (NO) synthase, were studied on ricinoleic acid-evoked contractions in rat isolated ileum. Ricinoleic acid (10(-5) to 10(-4) M) caused a concentration-dependent contraction. Addition of L-NAME (30-300 microM) or L-NMMA (30-300 microM) to the Tyrode's solution increased in a concentration-dependent fashion the amplitude of the ricinoleic acid-evoked responses. L-Arginine (900 microM), a natural substrate of NO synthase, but not D-arginine (900 microM), counteracted the effect of L-NAME (300 microM). The potentiating effect of L-NAME was also prevented by sodium nitroprusside (0.1-1 microM), a generator of NO. These results provide evidence that endogenous NO may modulate the contraction of rat ileum induced by ricinoleic acid. As the contraction induced by ricinoleic acid is not blocked by tetrodotoxin (0.6 and 6.0 microM) the contractile effect of ricinoleic acid results mainly from a direct action on the smooth muscle.

Increased ex-vivo colonic generation of PAF induced by diphenylmethane stimulant laxatives in rats, mice, guinea-pigs and rabbits

The effects of in-vivo treatment with bisacodyl, phenolphthalein, picosulphate, sulphosuccinate, mannitol and lactulose laxatives were examined on the ex-vivo formation of platelet-activating factor (PAF) by duodenum and colon of rat, mouse, guinea-pig and rabbit. Bisacodyl (10 mg kg-1), phenolphthalein (20 mg kg-1) and picosulphate (10 mg kg-1), but not sulphosuccinate (40 mg kg-1), mannitol (50 mg kg-1) or lactulose (50 mg kg-1), at doses that all caused laxation, markedly increased PAF in the colon (P < 0.01) but not in the duodenum. Intraluminal release of acid phosphatase was also significantly increased in the colon of rats treated with bisacodyl, phenolphthalein and picosulphate, but not in colons of animals treated with sulphosuccinate, mannitol or lactulose. The data show that enhanced generation of PAF is associated with the colonic damage induced by diphenylmethane laxatives, but do not show whether this is a cause or a consequence of the pathophysiological changes.

Effect of senna is not mediated by platelet-activating factor

The effect of in vivo treatment with senna was examined on the ex vivo formation of platelet-activating factor (PAF) by small and large intestine of rat, mouse and guinea pig. A single or a prolonged oral administration of senna (60-240 mg/kg) to animals did not increase intestinal PAF content. Nor did senna increase the intraluminal release of acid phosphatase. A similar result was obtained in the colonic tissue of rat perfused in vitro with rhein (1-500 micrograms/ml) or rhein anthrone (1-500 micrograms/ml). In contrast, a single oral administration of phenolphthalein (20 mg/kg), bile salts (20 mg/kg) or magnesium sulfate (30 mg/kg) to rats increased intestinal PAF content. Magnesium sulfate also increased the intraluminal release of acid phosphatase. Colonic tissue of rats perfused in vitro with calcium ionophore A23187 (10 micrograms/ml) formed large amounts of PAF and acid phosphatase. PAF stimulates intestinal motility and secretion and mediates gut damage while acid phosphatase is a marker of cellular damage. Therefore, our data suggest that senna is well tolerated in animals and PAF does not mediate senna-induced laxation.

Platelet activating factor and the responses of rat isolated stomach strip to prostaglandin E2

The effect of platelet activating factor (PAF) on contractions evoked by acetylcholine, 5-hydroxytryptamine (5-HT) and prostaglandin E2 (PGE2) was studied in-vitro on rat stomach strip. Addition of PAF to the organ bath increased PGE- but not 5-HT- or acetylcholine-evoked responses. The effect of PAF was unaffected by atropine, methysergide or indomethacin, but prevented by a specific PAF receptor antagonist BN 52021. The data support a specific interaction between PAF and PGE2 on rat stomach strip.

Inhibitors of nitric oxide synthetase prevent castor-oil-induced diarrhoea in the rat

1. Castor oil (2 ml orally) produced copious diarrhoea in rats 3 h after its administration. 2. Pretreatment (intraperitoneal, i.p.) of rats with the NO synthesis inhibitors NG-nitro-L-arginine methyl ester (L-NAME, 1-25 mg kg-1) and NG-monomethyl-L-arginine (L-NMMA, 2.5-100 mg kg-1) inhibited or prevented castor-oil-induced diarrhoea. L-Arginine (150-600 mg kg-1, i.p.) administered to rats pretreated with L-NAME 10 mg kg-1, drastically reduced the antidiarrhoeal activity of L-NAME in a dose-related manner. D-Arginine (900 mg kg-1) did not modify the protection by L-NAME. 3. Pretreatment (i.p.) of rats with L-NAME (2.5-25 mg kg-1) decreased the intestinal fluid accumulation and Na+ secretion induced by castor oil. L-Arginine (600 mg kg-1) but not D-arginine (900 mg kg-1) counteracted the inhibitory effect of L-NAME (10 mg kg-1). 4. L-NAME (10 and 25 mg kg-1) had no significant effect on the intestinal transit in normal rats or those given castor oil. 5. These results provide evidence that nitric oxide (NO) could play an important role in castor-oil-induced diarrhoea.

Mechanism of short-chain fatty acid uptake by apical membrane vesicles of rat distal colon

In this study, the presence of a bicarbonate gradient-dependent, carrier-mediated anion exchange process for butyrate (a representative short-chain fatty acid) uptake in apical membrane vesicles isolated from rat distal colon is described. An outward gradient of both butyrate- and bicarbonate-stimulated [14C]butyrate uptake and resulted in transient accumulation (an "overshoot" phenomenon). Butyrate gradient-stimulated [14C]butyrate uptake was not altered either by an imposed pH gradient or at different pH values. In contrast, bicarbonate gradient-stimulated [14C]butyrate uptake was stimulated severalfold by an additional imposition of an outward pH gradient (pHi = 7.5; pH0 = 6.0). This bicarbonate- and pH gradient-stimulated butyrate uptake was not inhibited by either voltage clamping, with equimolar intravesicular and extravesicular K+ and valinomycin, or 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid (DIDS), an anion-exchange inhibitor. Increasing butyrate concentrations saturated the bicarbonate- and pH gradient-stimulated butyrate uptake with a half-maximal concentration (Km) of 26.9 +/- 1.6 mmol/L. Butyrate uptake was substantially inhibited by 20 mmol/L propionate (45%) and acetate (60%) but was not inhibited by oxalate, inorganic anions (SO4(2-) and NO3-), and transport inhibitors (amiloride, acetazolamide, furosemide, and ouabain). It is concluded from these results that bicarbonate gradient-stimulated butyrate uptake in apical membrane vesicles of rat distal colon occurs via a carrier-mediated anion-exchange process that differs from other DIDS-sensitive anion exchanges [e.g., the Cl- -OH- (HCO3-) process].

Preliminary studies on antipyretic and analgesic properties of Taverniera abyssinica

In an attempt to ascertain the pharmacological basis of the use of the marketed traditional drug Taverniera abyssinica A. Rich. (Amharic name Dingetegna), crude extracts as well as purified substances of this plant were tested for their antipyretic and analgesic properties. Antipyretic activity was determined on rats made hyperthermic by yeast injection and analgesic activity was determined by the hot plate, as well as the acetic acid induced writhing, methods. The study showed that the plant possesses significant antipyretic and analgesic activities.

Castor oil increases intestinal formation of platelet-activating factor and acid phosphatase release in the rat

1. When castor oil was administered by gavage to rats, the duodenum and jejunum but not ileum and colon produced large amounts (5-6 fold greater than control) of platelet activating factor (Paf). 2. Intraluminal release of acid phosphatase (AP) was also markedly increased (5-6 fold greater than control) in the duodenum and jejunum of castor oil-treated rats and there was a correlation between the elevated release of AP and intestinal hyperaemia. 3. These findings support a role for Paf as a mediator of intestinal damage induced by castor oil.

Senna still causes laxation in rats maintained on a diet deficient in essential fatty acids

The laxative effect of senna has been investigated in normal and essential fatty acid deficient (EFAD) rats. Oral administration of senna pod extract (7-5-90 mg kg-1) produced a dose-dependent increase in the number of soft faeces excreted by normal rats. Senna 30 mg kg-1 also reversed net absorption of water and increased the prostaglandin (PG) production in the colonic lumen of normal rats by about four times. Oral administration of senna pod extract to rats, maintained on a fat-free diet for 30-90 days, produced diarrhoea and reversed net absorption of water as in normal rats. However, a fat-free diet reduced the PG production drastically in the colonic lumen both in senna-free rats and in senna-treated rats. In EFAD rats carrageenan oedema, but not dextran oedema, was also drastically reduced. Since PG mediation is not present in EFAD rats we conclude that the PG are not essential for laxation induced by senna and that water secretion and PG production in the rat intestinal lumen are unrelated.

Flavonoids, leucocyte migration and eicosanoids

Quercetin reduced the concentration of prostaglandin E2 (PGE2) and leukotriene B4 (LTB4) in the pleural exudate induced in rats by 1% carrageenan given intrapleurally. Leucocyte migration in the exudate was also reduced by the flavonoid. Inhibition of eicosanoids and leucocytes in the exudate was dose-related. Quercetin also reduced LTB4 synthesis in cells stimulated with ionophore A23187, either ex-vivo or in-vitro. A similar, though less active, mode of action was found with quercitrin, while apigenin and luteolin reduced leucocyte accumulation and PGE2 formation, but not LTB4-formation.

Potentiation by phenolphthalein of the responses of guinea-pig ileum and rat stomach strip to PGE2 and other agonists

Phenolphthalein was examined for its effect on the activity of isolated muscle (guinea-pig ileum and colon, rat stomach), and on the tissue responses to PGE2, histamine and 5-HT. The ileal circular muscle and both muscle layers of the colon were unaffected by phenolphthalein. In contrast, the laxative potentiated the responses of the longitudinal muscle of guinea-pig isolated ileum and the rat stomach strip to the agonists, particularly PGE2. This potentiation was reduced by indomethacin in vivo, but mepyramine or methysergide had little or no effect. Augmentation of muscle activity by phenolphthalein, particularly in the response to PGE2, may contribute to the laxative effect.

Evidence against a dependence of the senna effect on prostaglandin formation

The laxation induced by senna is not modified in rats either maintained on a diet deficient in essential fatty acids (EFAD) or exposed to cold (6 degrees C) or with yeast-induced fever. In light of our findings it appears conceivable that non-PG-mediated mechanism(s) play a relevant role in laxation induced by senna.

Effect of cholera toxin on the production of eicosanoids by rat jejunum

1 Cholera toxin injected i.v. into rats stimulated the production of prostaglandin E2 (PGE2), leukotriene B4 (LTB4) and LTC4 by segments of jejunum, but it had no effect when added to the tissue in vitro. 2 Pretreatment of the animals with the compound BW 755C reduced the increased production of PGE2, LTB4 and LTC4 by i.v. cholera toxin. Pretreatment with indomethacin reduced the production of PGE2. 3 These findings are consistent with the hypothesis that arachidonate metabolites are involved in the diarrhoea induced by cholera toxin.

Laxatives and the production of autacoids by rat colon

The effects of some laxatives were examined on the formation of histamine, 5-hydroxytryptamine (5-HT) and prostaglandin-like material (PG-LM) by rat intestine in-vitro. Castor oil, senna, sulphosuccinate and bisacodyl, but not mannitol or lactulose, in doses that cause laxation, increased the formation of histamine, 5-HT and PG-LM. Indomethacin or hydrocortisone reduced the increase of PG-LM formation. The data support the idea that the laxative effects of these intestinal secretagogues are due to increased intestinal production of PG-LM, histamine and 5-HT.

Phenolphthalein stimulates the formation of histamine, 5-hydroxytryptamine and prostaglandin-like material by rat jejunum, ileum and colon

The effects of phenolphthalein on the formation of histamine, 5-hydroxytryptamine(5-HT) and prostaglandin-like material by rat intestine were examined in vivo. Phenolphthalein, in a dose that causes laxation increased the formation of histamine, 5-HT and prostaglandin-like material, and indomethacin reduced these increases. The data support the idea that the laxative effect of phenolphthalein is due to increased intestinal production of prostaglandin, histamine and 5-HT.

Suppression of laxative action of phenolphthalein by orally-administered indomethacin or aspirin

Oral administration of phenolphthalein produced a dose-dependent increase of wet faeces excreted by mice. The response to phenolphthalein was reduced by pretreatment with indomethacin, aspirin or polyphloretin phosphate (PPP), but not with benoxaprofen. These findings support the view that the effect of phenolphthalein may be suppressed by PG synthetase inhibitors (indomethacin, aspirin) and by PPP.

Influence of ricinoleic acid on the contractions elicited by PGE2 on the guinea-pig ileum

The effect of ricinoleic acid on prostaglandin E2 (PGE2)-evoked contractions was studied on guinea-pig isolated ileum. Addition of ricinoleic acid (10 micrograms ml-1) to the organ bath increased the amplitude of the PGE2-evoked responses. Ricinoleic acid (10 micrograms ml-1) also sensitized the guinea-pig isolated ileum to acetylcholine and histamine. The effect of the ricinoleic acid was greatly reduced by indomethacin either in-vivo (10 mg ml-1) or in-vitro (2 micrograms ml-1).

Antipyretic and antibacterial actions of Teucrium polium (L.)

The antipyretic and antibacterial activities of the ethanolic extract of the flowering tops of Teucrium polium (L.) were been studied. The extract was effective against both yeast and carrageenin pyrexia in rats. It also exhibited a marked antibacterial action against both gram positive and gram negative organisms and was found to be non toxic in acute studies.

Phytotherapeutic profile of some plants used in folk medicine

The effect of nine vegetable extracts was evaluated on the carrageenin-induced oedema in the rat. Our results show that the above extracts are able to exert - at different degree - a very marked decrease of the inflammed site related to the presence in the considered plants of several active biologically compounds as sterols and flavonoids. Preliminary chemical analysis of these vegetables are also reported.

Effect of indomethacin on aloin and 1,8 dioxianthraquinone-induced production of prostaglandins in rat isolated colon

The effect of aloin and 1,8 dioxyanthraquinone on the release of prostaglandin-like material (PG) from rat isolated colon has been investigated. Orally administered aloin and 1,8 dioxyanthraquinone stimulates PG production by subsequently isolated segments of colon. Indomethacin was able to prevent this increased production of PG. These results suggest that the laxative properties of aloin and 1,8 dioxyanthraquinone may depend, at least in part, on increased prostaglandin synthesis by the intestinal tissue.

Enhancement by levamisole of the contractions induced by prostaglandin E2 in the guinea-pig isolated ileum

The effect of levamisole on prostaglandin E2 (PGE2)-evoked contractions was studied on guinea-pig isolated ileum. Addition of levamisole (10 micrograms/ml) to the organ bath produced a pronounced increase in the amplitude of the PGE2-evoked responses. Levamisole (10 micrograms/ml) also sensitized the guinea-pig isolated ileum to 5-hydroxytryptamine and bradykinin, but not to histamine. The effect of the levamisole was not due to stimulation of autonomic ganglia or cholinergic activity since it was unaffected by hexamethonium or atropine, but it was prevented by indomethacin.

Endogenous inhibitor of prostaglandin biosynthesis in inflammation

Rat serum exhibits a concentration-related inhibition of PG biosynthesis by rat peritoneal leucocytes phagocytosing killed bacteria. The serum inhibitory potency is increased by inducing carrageenan foot oedema in animals whereas it is not altered by dextran oedema. The increase of the inhibitory activity of serum from carrageenan-treated rats develops in a time-dependent way reaching its maximum at 24 h. Since the increased inhibitory activity does not occur following indomethacin administration we suggest that PG formation at the inflammatory site may stimulate the ability of serum to inhibit PG biosynthesis.