Cimetidine inhibits nitric oxide associated nitrate production in a soft-tissue inflammation model in the horse

Effects of the histamine H2 receptor antagonist famotidine on the healing of colonic anastomosis in rats

BACKGROUND

Failure of anastomotic healing is one of the major complications in colorectal surgery. Because histamine plays an important role in immune and inflammatory reactions, we demonstrate the effects of famotidine on the healing of colonic anastomosis in rats.

METHODS

Twenty-eight Sprague-Dawley rats were used in the study. Excision and end-to-end anastomosis was performed in the distal colon of the rat. The Famotidine Group received 2 mg/kg/day famotidine; the Control Group received the same amount of saline. Bursting pressure of anastomoses and hydroxyproline content of perianastomotic tissues were evaluated on the third and seventh days following surgery.

RESULTS

Bursting pressures and hydroxyproline contents for the Famotidine Group were significantly lower than the equivalent parameters for the Control Group on both the third and seventh days post-surgery.

CONCLUSIONS

According to our findings, famotidine exerts detrimental effects on the anastomotic bursting pressure and hydroxyproline content of perianastomotic tissues in the colon of rats.

Multiple dose pharmacokinetics and acute safety of piroxicam and cimetidine in the cat

The purpose of this study was to evaluate the multiple dose pharmacokinetics and acute safety of piroxicam and cimetidine alone and in combination in cats. Seven healthy cats were included in this randomized-crossover study. The cats were assigned to groups designated to receive cimetidine alone (15 mg/kg, p.o., q12 h), piroxicam alone (0.3 mg/kg, p.o., q24 h), and piroxicam combined with cimetidine (both at aforementioned doses). The cats were dosed for 10 days followed by at least a 2-week washout period between trials. Serial blood samples were collected following the first and last doses and analyzed utilizing a high-performance liquid chromatography with mass spectrometry detection (LC/MS) assay. Pharmacokinetic parameters were determined using noncompartmental analysis. Endoscopic evaluation of the gastric mucosa was performed and serum urea nitrogen (SUN), creatinine, alkaline phosphatase (ALP), and alanine transaminase (ALT) activities were evaluated. There were not a clinically relevant difference between the pharmacokinetic parameters of piroxicam administered alone or in combination with cimetidine after either the first or last dose. Gastric ulcers were not observed in any cats although gastric erosions were. The SUN, creatinine, ALP, and ALT activities remained within reference ranges for all cats. It appears that once daily, short-term use of piroxicam alone and in combination with cimetidine in cats is relatively safe based on the parameters evaluated in this study. However, further studies are necessary to determine the long-term gastrointestinal safety of piroxicam.

Concentrations of nitric oxide in equine preovulatory follicles before and after administration of human chorionic gonadotropin

In the present study, follicular fluids of estrous mares treated with saline solution (Control) or nitric oxide synthase (NOS) inhibitors were analyzed for nitric oxide (NO), estradiol-17beta (E2) and progesterone (P4) concentrations before and 36h after administration of human chorionic gonadotropin (hCG). Follicular fluids obtained before (0h) hCG administration from control mares had lower concentrations of NO than those obtained 36h after administration of hCG (58.3+/-17.8 micromol versus 340.4+/-57.7 micromol; P<0.05). A similar pattern was also noted for intrafollicular P4 in control mares, which had lower concentrations of intrafollicular P4 before hCG than 36h post-hCG administration (P<0.05). As expected, E2 concentrations of control follicles sampled before hCG administration were higher than those sampled 36h post-hCG administration (P<0.05). However, the E2 concentrations in follicles of mares treated with the NOS inhibitors N(omega)-nitro-L-arginine methyl ester (L-NAME) or aminoguanidine (AG) did not decrease after hCG administration, unlike those in control mares (P>0.10). In addition, mares treated with NOS inhibitors had lower intrafollicular concentrations of NO and P4 than control mares, both before and after hCG administration (P<0.05). Increased intrafollicular concentrations of NO in control, hCG-stimulated mares provide evidence for the presence of an NO-generating system in the equine preovulatory follicle that is likely upregulated following administration of hCG.

Nitric oxide, inducible nitric oxide synthase and inflammation in veterinary medicine

Inflammation is a process consisting of a complex of cytological and chemical reactions which occur in and around affected blood vessels and adjacent tissues in response to an injury caused by a physical, chemical or biological insult. Much work has been performed in the past several years investigating inducible nitric oxide synthase (NOS, EC 1.14.13.39) and nitric oxide in inflammation. This has resulted in a rapid increase in knowledge about iNOS and nitric oxide. Nitric oxide formation from inducible NOS is regulated by numerous inflammatory mediators, often with contradictory effects, depending upon the type and duration of the inflammatory insult. Equine medicine appears to have benefited the most from the increased interest in this small, inflammatory mediator. Most of the information on nitric oxide in traditional veterinary species has been produced using models or naturally occurring inflammatory diseases of this species.

Effect of nitric oxide synthase inhabitors on ovulation in hCG-stimulated mares

Recent studies suggest that nitric oxide (NO) may have a role in regulating ovarian physiology. To investigate the role of NO during ovulation in mares, inhibitors of the nitric oxide synthase (NOS) were administered to estrous mares. Forty cycling mares (20 horses and 20 pony mares) were allotted to one of the three treatment groups. Once a follicle was at least 27 mm in diameter, but smaller than 35 mm, mares were given one of the following treatments: saline solution 0.9% (n = 20, w/v, i.v., every 12 h), Nomega-nitro-L-arginine methyl ester hydrochloride (L-NAME; n = 10, 148 micromol/kg, i.v., every 12 h), or aminoguanidine hemisulfate (AG; n = 10, 406 micromol/kg, i.v., every 12 h). When a follicle >30 mm was present on one of the ovaries, ovulation was induced with hCG (2,500 IU, i.v.). The median time of ovulation (+/-6 h) after hCG administration for the treatment groups was 42, 84 and 54 h for mares treated with saline solution, L-NAME and AG, respectively. There was no significant difference between the groups treated with AG or L-NAME (P = 0.06); however, these groups were different from the control group (P < 0.05). The delayed ovulation caused by the administration of NOS inhibitors suggests a role for NO in follicular growth and ovulation in horses.

Blockade of histamine H2 receptors attenuate blood-brain barrier permeability, cerebral blood flow disturbances, edema formation and cell reactions following hyperthermic brain injury in the rat

Role of histamine H2 receptors in blood-brain barrier (BBB) disturbances, cerebral blood flow (CBF), brain edema formation, and cell injury caused by heat stress in a rat model was examined using the pharmacological approach. Blockade of histamine H2 receptors by cimetidine or ranitidine significantly attenuated the BBB permeability to Evans blue albumin and [131]I-sodium extravasation, brain edema formation and cell injury following 4 h heat stress in rats at 38 degrees C. These drug treatments also restored the CBF to near normal values. These beneficial effects in heat stress were most marked in rats treated with ranitidine compared to cimetidine given in identical dosage. Our observations suggest that blockade of histamine H2 receptor is beneficial in hyperthermic brain injury and indicates that histamine is involved in the pathophysiology of heat stress induced brain dysfunction. Our study strongly suggests further need to develop more specific and sensitive histaminergic H2 receptor blockers for the treatment of neurological ailments.