Effect of extracellular volume expansion and surgical stress on splanchnic blood flow and cardiac output in anesthetized rats: role of nitric oxide

Protective effects of aminoguanidine on enteric cholinergic neurons and gastrointestinal motility in starved rats

AIM: To investigate the changes in enteric cholinergic neurons and intestinal transit in starved rats and to explore the protective mechanism of aminoguanidine (AG) on enteric nervous system and gastrointestinal motility.

METHODS: Ninety male Sprague-Dawley rats were randomly divided into three groups: normal control group (n = 10), starvation group (n = 40) and AG group (n = 40). The starvation group and AG group were further divided into four subgroups for testing on 3, 5, 7 and 9 days after starvation. The AG group was intraperitoneally injected with AG 150 mg/(kg•d) from the first day of starvation. Rats were killed on days 3, 5, 7 and 9 after starvation to take intestinal samples. The rate of intestinal transit was assessed with dextran blue-2000. The distribution density of cholinergic neurons in the ileal myenteric plexus were evaluated by acetylcholinesterase (AChE) histochemistry.

RESULTS: The rates of intestinal transit were significantly lower at all time points after starvation in the starvation group and AG group than in the control group (all P < 0.05 or 0.01). The rates of intestinal transit in the starvation group and AG group decreased with time, reaching the lowest point on day 9. However, the rates of intestinal transit were significantly higher on days 3, 5 and 7 in the AG group than in the starvation group (52.2% ± 4.7% vs 47.5% ± 4.2%, 49.8% ± 5.6% vs 42.3% ± 5.4%, and 43.3% ± 6.4% vs 36.6% ± 5.2%, all P < 0.05) though there was no obvious difference on day 9. The density of cholinergic neurons was significantly lower in the starvation group and AG group than in the control group at all time points (allP < 0.01). The density of cholinergic neurons in the starvation group and AG group decreased with time, reaching the lowest point on day 9. The density of cholinergic neurons was significantly higher on days 5 and 7 in the AG group than in the starvation group (both P < 0.05) though there was no obvious difference on days 3 and 9.

CONCLUSION: Early intraperitoneal supplement of aminoguanidine is helpful in promoting enteric nervous system function and intestinal transit in starved rats.

Changes in nitric oxide production in the rat kidney due to CaOx nephrolithiasis

AIMS

The aim of the study was to test the hypothesis that the renal nitric oxide (NO) system is involved in the animal model of nephrolithiasis by evaluating the relationship between nitric oxide synthase (NOS) and oxidative stress.

METHODS

Deposition of renal calculi was induced by adding 0.75% ethylene glycol (EG) to the drinking water of male Wistar rats. After 42 days of treatment, urinary biochemistry and urinary levels of oxalate, NO metabolites (nitrate and nitrite), cGMP, and lipid peroxides, and markers for renal damage and oxidative stress in the kidney were examined. In the second part of the experiment, two diuretic stimuli (intrarenal infusion of l-arginine or saline loading) were applied to test the renal NO system response. Finally, levels of three isoforms of NOS in renal tissues were evaluated by immunostaining.

RESULTS

In the EG-treated rats, increased urinary excretion of enzymes and lipid peroxides and increased nitrotyrosine levels and oxidative injury markers in the kidneys indicated that peroxynitrite formation occurred during oxidative stress, while the 24-hr urinary excretion of NO metabolites and cGMP remained unchanged. In contrast to control rats, urinary excretion and NO metabolites and cGMP excretion were unresponsive to intrarenal l-arginine infusion; in response to saline loading, an increase in these factors was seen, but the increase was only 50% of that seen in the identically treated control group. A significant decrease in eNOS expression and increase in iNOS expression were observed in the renal medulla of the EG-treated group, whereas expression of nNOS was not affected.

CONCLUSIONS

Although basal renal NO production remained unchanged, excessive peroxynitrite formation in the kidney was noted in this model. A decreased response of the NOS system was noted when diuretic stimuli were applied. How the imbalance between eNOS and iNOS expression influences CaOx stone formation requires detailed evaluation.