Cirrhosis serum induces a nitric oxide-associated vascular hyporeactivity of aortic segments from healthy rats in vitro.

OBJECTIVE: Arterial vasodilation with concomitant hyperdynamic circulation are common findings in liver cirrhosis. Nitric oxide acting at a local level has been suggested to be pathophysiologically relevant in this context. Several systemic factors in conjunction with nitric oxide might interfere with the observed phenomena. DESIGN: The study has been designed to demonstrate the influence of cirrhotic serum on the nitric oxide system and vascular contractility. METHODS: The contractile response of aortic segments from healthy rats was studied in vitro after incubation with serum of healthy and cirrhosis-induced rats (1 week, 2 weeks, 3 weeks and 4 weeks after bile duct ligation). A cumulative dose response curve to phenylephrine (10--10-4 mol) was established before and after incubation with nitric oxide synthesis blocker N(omega)-nitro-L-arginine, the more selective aminoguanidine (nitric oxide synthase [NOS]-2 inhibitor) and W7 (NOS-3 inhibitor). NOS-2 expression in incubated aortic rings was evaluated by Western blot analysis. RESULTS: A 4-hour incubation with serum of cirrhosis-induced rats reduced the maximum contractile response to phenylephrine to 66.8 +/- 9.1% after 1 week, 50.4 +/- 7.8% after 2 weeks, 43.2 +/- 2.8% after 3 weeks and 35 +/- 5.2% after 4 weeks of bile duct ligation. This reduction in the contractility response to phenylephrine was completely reversed by blocking nitric oxide synthesis with N(omega)-nitro-L-arginine and aminoguanidine, but not after W7. Incubation with cirrhotic serum induced NOS-2 expression in aortic rings. In Western blot analysis, the most intensive signal for NOS-2 protein was obtained in rings incubated with serum from rats 3 weeks and 4 weeks after induction of cirrhosis. CONCLUSIONS: Cirrhotic serum decreases the contractile response to phenylephrine even in an early stage of secondary cirrhosis. Reversibility of this effect after nitric oxide synthesis blockade suggests an induction of nitric oxide synthesis by systemic factors as a major point in vascular hyporeactivity to vasoconstrictors in cirrhosis.

Non-adrenergic, non-cholinergic regulation of stone-diseased and stone-free human gallbladders.

OBJECTIVE: The aim of this study was to determine the role of nitric oxide (NO), as the primary neurotransmitter of non-adrenergic, non-cholinergic (NANC) innervation, in stone-diseased and stone-free human gallbladders. METHODS: Human gallbladder muscle strips were mounted in modified Krebs-Henseleit solution with atropine (1 mM), guanethidine sulfate (5 mM) and aerated with Carbogen. Electric field stimulation (EFS) (70 V, 0.5 ms, 100 pulses) was used to activate NANC nerves. N-omega-nitro-L-arginine (L-NNA, 100 mM) and L-arginine (L-Arg, 120 mM) were used to manipulate the NO-synthase. Gallbladder slices were stained by using the alkaline phosphatase, anti-alkaline phosphatase (APAAP) method for histological examination. RESULTS: In the control group (basal tone, 8.94 +/- 1.17 mN) caused a frequency-dependent reduction of basal tone (1 Hz = 5.73 +/- 0.81 mN; 3 Hz = 5.18 +/- 0.65 mN; 10 Hz = 4.63 +/- 0.49 mN), inhibition of NO-synthesis with L-NNA increased the tone (7.63 +/- 0.76 mN). Stone-diseased groups were divided into two groups (contractor and subcontractor), according to their ability to contract by CCK. Under the influence of EFS the contractor group (basal tone = 7.79 +/- 0.93 mN) reacted like the control group, but was frequency-independent and, additionally, showed spontaneous phasic contractions. In the sub-contractor group (basal tone 4.13 +/- 0.65 mN) EFS only decreased the frequency of spontaneous phasic contractions. L-NNA caused an increase in tone (5.97 +/- 0.84 mN) and frequency. L-arginine, the substrate for NO-synthase, significantly reversed this effect, indicating the dependence on NO. Histologically, the contractor group showed a wrinkled mucosal membrane and low-grade inflammation. Shallow mucosa, necrosis and high-grade inflammation were found in the sub-contractor group. CONCLUSIONS: In vitro, NANC relaxation of human gallbladder is NO dependent. The motility of stone-diseased gallbladders is modulated by NO and seems to depend on the degree of scarification.

A randomized, double-blind trial for stress ulcer prophylaxis shows no evidence of increased pneumonia.

BACKGROUND: H2-receptor antagonists are commonly used for stress ulcer prophylaxis on intensive care units. However, there is evidence that via the route of an elevated gastric pH, followed by bacterial overgrowth and subsequent tracheal aspiration, pneumonia could occur. In line with this assumption total gastrectomized patients should develop a very high incidence of pneumonia, which is actually not the case. We therefore formulated the hypothesis that stress ulcer prophylaxis with H2-receptor antagonists does not lead to an increased pneumonia rate. METHODS: A total of 158 patients with mechanical ventilation > or =48 hours of a surgical intensive care unit were randomized to the following groups: A, placebo (n = 57); B, pirenzepine (3 x 10 mg intravenously, n = 44); and C, ranitidine (3 x 50 mg intravenously, n = 57). RESULTS: The pneumonia rate in ranitidine-, pirenzepine-, and placebo-treated patients is 10 of 57, 10 of 44, and 12 of 57, respectively. CONCLUSIONS: Pneumonia rate is not adversely affected by H2-receptor antagonists in stress ulcer prophylaxis.

An improved model for rat liver transplantation including arterial reconstruction and simplified microvascular suture techniques.

For experimental liver transplantation in the rat, the models that have been used most frequently do not include reconstruction of the arterial blood supply to the liver. In these procedures, specially developed cuff anastomoses rather than the conventional microvascular suture technique are used almost exclusively in the recipient operation, so that the anhepatic time is minimized. In this study the technical details of an improved rat model for orthotopic liver transplantation are described. During the donor operation in this experimental method, the liver is prepared with an arterial pedicle that includes the abdominal segment of the aorta, permitting perfusion in situ of the portal vein as well as the hepatic artery. The transplantation of the excised donor organ into the recipient site is carried out with simplified microvascular suture techniques and includes reconstruction of the arterial supply to the liver. Anastomosis of the bile duct is accomplished by choledocho-choledochostomy with a splint technique and supplemental suturing. For the entire procedure, magnifying glasses with 2- to 2.5-fold magnification are sufficient. When this technique has been mastered, the average duration of the anhepatic phase is about 20 min, well below the critical 30-min limit for survival of the experimental animals. As proficiency increased, the perioperative mortality was reduced to 9.2% (n = 130). With the combination of portal and arterial in situ flushing during the donor operation and the rearterialization of the transplant during the recipient operation, the clinical conditions can be approximated more closely than is possible when the transplanted rat liver is supplied only by the portal vein. Use of microvascular suture techniques, without cuff anastomoses, reduces the need for ex situ handling of the donor organ.