Biomedical subjects

Zsolt Palásthy

Publications and source records attributed to Zsolt Palásthy.

2 recordsLinked to original sources

PubMed2006

Intestinal nitric oxide synthase activity changes during experimental colon obstruction.

OBJECTIVE: The experiments in this study were designed to follow the time course of nitric oxide (NO) synthesis in the large bowel during acute mechanical ileus. MATERIAL AND METHODS: Occlusion of the mid-transverse colon was maintained for 420 min in anesthetized dogs. Strain-gauge transducers were used to analyze motility changes on the hepatic and lienal flexures, respectively. Constitutive NO synthase (cNOS) and inducible NOS (iNOS) activities were determined in tissue biopsies, and plasma nitrite/nitrate (NOx) level was measured in the portal blood. Following completion of the baseline studies, the animals were treated with either 7-nitroindazole (7-NI, selective neuronal NOS inhibitor), or N-nitro-L-arginine (NNA, non-selective NOS inhibitor). RESULTS: In the sham-operated group the cNOS activities differed significantly in the oral and aboral tissue samples (oral: 102.9; versus aboral: 62.1 fmol/mg protein/min). The obstruction elicited a significant increase in portal NOx and elevated tissue inducible NO synthase (iNOS) activity. NNA treatment decreased the motility index in both intestinal segments for 60 min, but 120 min later the motility index was significantly elevated (2.5-fold increase in the oral part, and 1.8-fold enhancement in the aboral segment, respectively). Treatment with 7-NI decreased the cNOS activity in the oral and aboral parts by approximately 40% and 70%, respectively, and suppressed the motility increase in the aboral colon segment. CONCLUSIONS: The motility of the colon was either significantly increased or decreased, depending on the type and selectivity of the NOS inhibitor compounds applied. NO of neuronal origin is a transmitter that stimulates peristaltic activity; but an increased iNOS/nNOS ratio significantly moderates the obstruction-induced motility increase.

Animals↗

PubMed2005

[Dual effects of nitric oxide in acute colon obstruction].

UNLABELLED: Nitric oxide (NO) plays central role in the pathophysiology of large bowel diseases. In the gastrointestinal tract the predominant form of nitric oxide synthase (NOS) isoenzymes is neuronal NOS (nNOS). The aims were to investigate the role of NO and the activation of NOS isoforms during acute colonic obstruction. Haemodynamic changes, large bowel motility and plasma levels of nitrate-nitrite (NOx) were observed for 7 hrs in anaesthetized dogs. Group 1 (n=6) served as sham-operated control. In groups 2 (n=8), 3 (n=6), and 4 (n=6) colon obstruction was initiated. Groups 3 and 4 were treated with non-selective NOS inhibitor N-nitro-L-arginine (NNA, 4 mg/kg) or with the selective nNOS inhibitor 7-nitroindazol (7-NI, 5 mg/kg) 3 hr after the obstruction. At the end of the experiments, tissue biopsies were taken from the oral and aboral parts of the colon to determine the constitutive and inducible NOS (cNOS and iNOS, respectively) activities. RESULTS: The cNOS activity of the colon was significantly higher orally then aborally in each group. After obstruction the characteristic features of hyperdynamic sepsis were observed. The obstruction caused significant increase in iNOS activity, which was significantly reduced by the NOS inhibitors. The obstruction increased the motility on both parts of the colon. The administration of NNA transiently inhibited, but later significantly increased the motility of the colon segments. Inhibition of nNOS by 7-NI treatment did not influence the hemodynamic parameters but decreased the motility. CONCLUSION: Neuronal NO increases colon motility at the early stage of large bowel obstruction, however, during a concomitant sepsis the excess of inducible NO will moderate this effect.

Acute Disease↗