Vasoactive intestinal polypeptide potentiates the hypoxemia-induced decrease in splanchnic circulation in the rat

Nitric oxide synthesis inhibition: the effect on rabbit pyloric muscle

The relaxation mechanism of the pyloric smooth muscle is largely dependent on a nonadrenergic noncholinergic (NANC) inhibitory innervation mediated in part by nitric oxide (NO). The aim of the present study was to investigate the effect of NO antagonists on the contractility of the pyloric smooth muscle. In the clinical trial, 10 anesthetized experimental rabbits were infused intraarterially with the NO synthesis inhibitor N-nitro-L-arginine (L-NNA), at a concentration of 10(-4) mol/L; 10 controls received normal saline intraarterially. Pyloric contractility was assessed by balloon manometry. L-NNA infusion produced a dose-dependent increase in the frequency of the pyloric contraction. The maximal increase in frequency occurred during the slow L-NNA infusion rate of 146 ng/min (baseline-adjusted frequencies of experimental v control: 1.267 +/- 0.389 v 0.632 +/- 0.375; P = .001). The increased frequency level was sustained over the subsequent fast infusion rate of 292 ng/min (experimental v control: 1.362 +/- 0.604 v 0.704 +/- 0.579; P = .022). Both the duration and the amplitude of the pyloric contractions were not affected by the L-NNA infusion. These findings suggest that blockage of the L-arginine-NO pathway may have resulted in inhibition of the NANC-induced gastric muscle and relaxation of the pyloric sphincter. The authors speculate that the decreased NO production may be responsible for the sustained contraction of the pyloric smooth muscle with secondary hypertrophy, characteristic of hypertrophic pyloric stenosis.

Vasoactive intestinal polypeptide causes relaxation of the pyloric sphincter in the rabbit

Vasoactive intestinal peptide (VIP), which causes relaxation of gastrointestinal smooth muscle, has been found in high concentrations in the pylorus in many animal species, suggesting a prominent role for VIP in the control of pyloric sphincter function. We infused VIP into the gastric artery of 6 rabbits at rates from 12 to 1,200 ng/min and measured the intensity, duration, and frequency of spontaneous pyloric contractions with an intraluminal balloon and electromyography. VIP produced a dose-dependent reduction in the intensity (55% +/- 15% of baseline, P < .001) and the duration (29% +/- 25%, P < .001) of pyloric contraction. Maximal inhibition was observed at an infusion rate of 240 ng/min. The frequency of contractions did not decrease significantly in response to VIP infusion. Neostigmine infusion increased the intensity of pyloric contraction in a dose-dependent manner in doses of 0.10, 0.15, and 0.25 mg (140% +/- 78%, 273% +/- 76%, and 357% +/- 26% of baseline, respectively; P < .001). VIP infusion at 12 ng/min and 480 ng/min completely inhibited the increased intensity of contraction at neostigmine doses of 0.10 and 0.15 mg, respectively. Our results show that VIP decreases the intensity and the duration of pyloric contraction in a dose-dependent manner. As pyloric spasm may contribute to the pathogenesis of hypertrophic pyloric stenosis, we can postulate a role for reduced VIP-induced relaxation in the pathophysiology of hypertrophic pyloric stenosis.

Indium 111 oxine-labeled leukocytes for early diagnosis of ischemic enterocolitis

The feasibility of the use of indium 111 oxine-labeled autologous leukocytes for the diagnosis of ischemic enterocolitis in vivo was examined in an experimental model of ischemia in dogs. A 30-cm segment of small intestine was devascularized by ligating the arteries and veins from the last arcade in 7 dogs. A sham operation was performed in 3 control dogs. 111In oxine-labeled autologous white blood cells were infused 3.5 hours after operation. Anterior and lateral nuclear scanning was performed at 6 and 24 hours postinfusion with a gamma camera equipped with a low-energy magnifying multihole collimator. The animals were killed after 24 hours. The gross and microscopic appearance of the bowel was evaluated. The radioactivity in the serial specimens of the bowel was measured. In vivo scans were positive (ie, increased uptake in the bowel loop) in all dogs with intestinal ischemia at 6 and 24 hours. No significant uptake was noted in control dogs. Rectilinear scan of the bowel removed at autopsy showed a correlation between the area of infarction and tracer accumulation. In addition, there was a progressive decrease in uptake of 111In oxine from the center of the ischemic lesions to the periphery. Forty percent of the total radioactivity was measured at the center of the lesion, whereas only 6.5% was present at 22.5 cm from the center. Thus the ratio between the ischemic and normal tissue was 10:1 (range, 6.5 to 16). These studies demonstrate that 111In oxine-labeled autologous white blood cells can be used for the diagnosis of ischemic enterocolitis.(ABSTRACT TRUNCATED AT 250 WORDS)