Masaru Ohsuga

Intrapulmonary vascular dilatation and nitric oxide in hypoxemic rats with chronic bile duct ligation.

BACKGROUND/AIMS Nitric oxide (NO) has been suggested as the major cause of pulmonary vascular dilatation and hypoxemia in hepatopulmonary syndrome (HPS). The aim of this study was to assess the effect of NO on arterial oxygenation in rats with common bile duct ligation (CBDL rats), a model of HPS. METHODS Arterial blood gases were measured in 44 CBDL rats and 44 Sham rats under unrestrained conditions. Intrapulmonary shunting was assessed with (141)Ce-labeled microspheres (15-mum diameter) and serum nitrate/nitrite levels were measured by HPLC. The effect of NOS inhibition on A-aDO(2) was studied using L-NAME. RESULTS A decrease of PaO(2) below 82.7 mmHg (the mean value-2sigma in Sham rats) was seen in 43% of CBDL rats. Intrapulmonary shunting was greater in CBDL rats than in Sham rats (P<0.001). A correlation between the extent of shunting and A-aDO(2) was found in all animals studied (r=0.89, P<0.001, n=16). Serum levels of nitrate/nitrite increased significantly across the lungs, and the increase was significantly correlated with A-aDO(2) in the total population of animals studied. Administration of L-NAME to CBDL rats achieved a significant improvement of A-aDO(2). CONCLUSIONS These results suggest that pulmonary vascular dilatation due to NO leads to hypoxemia in CBDL rats.

Pulmonary blood transit time and impaired arterial oxygenation in patients with chronic liver disease.

BackgroundContrast-enhanced echocardiography (CEE) using agitated saline can detect intrapulmonary vasodilatation (IPVD) in patients with hepatopulmonary syndrome (HPS). We estimated the pulmonary transit time of erythrocytes (PTT) by CEE, using microbubbles, and studied its relationship to arterial oxygenation in chronic liver disease.MethodsSixteen patients with chronic liver disease and seven healthy subjects were studied. PTT was defined as the time between opacification of the right atrium and left atrium on CEE, using human serum albumin-air microbubble complexes with a mean diameter of 4 µm (Albunex). IPVD was detected by CEE with agitated saline. Arterial blood gases were analyzed with patients in the supine position, and while they were seated. Cardiac output (CO) was determined by Doppler echocardiography.ResultsThe mean PTT value for all of the patients was 4.0 ± 1.4 s. One of the 3 patients who showed IPVD was normoxemic. Mild orthodeoxia was observed in the patients with abnormal alveolar-arterial oxygen difference (A-aDO2) values (>15 mmHg), but not in those with normal A-aDO2 values, or in the healthy subjects. PTT was correlated with PaO2 (r = 0.52; P < 0.05; n = 16) and A-aDO2 (r = −0.54; P < 0.05; n = 16) in the seated position. CO was significantly correlated with PTT (r = −0.62; P < 0.05; n = 15), but not with PaO2 and A-aDO2, in both positions.ConclusionsPTT may be a useful parameter for evaluating arterial oxygenation in patients with chronic liver disease with early HPS.

Long-term haemodynamic effects of a 4-week regimen of nipradilol, a new β-blocker with nitrovasodilating properties, in patients with portal hypertension due to cirrhosis: A comparative study with propranolol

To study the long-term effects of pharmacological combination therapy, a comparison was made of the haemodynamic changes in patients with cirrhosis and portal hypertension following a 4-week treatment of propranolol or nipradilol, a new nonselective beta-blocker with nitrovasodilating effect. Nipradilol (12 mg/dag, n = 12) significantly diminished wedged hepatic venous pressure (WHVP, 25 +/- 16%), the hepatic venous pressure gradient (HVPG, 20 +/- 12%), and estimated hepatic blood flow (EHBF, 18 +/- 16%). Propranolol (30 mg/day, n = 11) also caused a significant reduction in WHVP (22 +/- 21%) and HVPG (24 +/- 21%), but not in EHBF. The percentage of portal pressure reduction and the frequency of nonresponders did not differ between the nipradilol and propranolol groups. Both agents reduced heart rate by approx. 20%. Nipradilol, however, did not cause a significant reduction in cardiac index (CI) versus a 14% reduction by propranolol. Pulmonary capillary wedge pressure and central venous pressure, an index of preload, were decreased slightly in the nipradilol group. When nonresponders were excluded, there was a significant correlation of the percentage of reduction between WHVP and CI or systemic vascular resistance, in the nipradilol group. These results indicate that nipradilol may have potent hypotensive effects on portal hypertension, similar but not superior to propranolol. Nipradilol, at the dosage used in the present study, did not appear to exert a nitrovasodilating effect to enhance the portal pressure reduction induced by beta-blocking action.

Arterial hypoxemia and intrapulmonary vasodilatation in rat models of portal hypertension.

BackgroundRats with chronic bile duct ligation (CBDL) and portal vein ligation (PVL) are used as models of portal hypertension. CBDL rats show hypoxemia with intrapulmonary vasodilatation (IPVD), and are recognized as a model of hepatopulmonary syndrome (HPS), while PVL rats are normoxemic. We investigated the differences in arterial oxygenation between these models, and the key factors leading to HPS.MethodsForty-eight Sprague-Dawley rats were prepared as CBDL or PVL models, or as Sham rats. Arterial oxygenation, hemodynamics (reference sample method), and IPVD were simultaneously evaluated in conscious and unrestrained animals, using 141Ce- or 113Sn-labeled microspheres (15 µm in diameter), respectively. Endothelin-1 (ET-1) and nitrate/nitrite (end products of nitric oxide; NOx) production by the lung tissue (increment across the lungs) was also determined.ResultsThe extent of IPVD was similar in both models, but hypoxemia was only observed in CBDL rats. The ET-1 level and the increment in NOx were significantly increased in CBDL rats, and the increment was directly correlated with impairment of oxygenation. Blood flow through the bronchial arteries (anatomical shunting) was increased in CBDL rats, reaching more than three times the level in PVL rats or Sham rats.ConclusionsThese results support the hypothesis that NO derived from the lung tissues contributes to hypoxemia, and IPVD appears to be a prerequisite for impaired oxygenation. The considerable increase of anatomical shunting may potentially contribute to impaired oxygenation in CBDL rats.

An alkaline thiol proteinase in the liver mitochondria of bullfrog, Rana catesbeina

The mitoplasts were prepared from bullfrog (Rana catesbeiana) liver mitochondria by treatment with digitonin and were then separated into the matrix and inner membrane fractions. The matrix fraction thus obtained was free of lysosomal contaminations and exhibited a distinct proteinase activity. pH dependency of the matrix proteinase activity measured in the presence and absence of iodoacetamide revealed that the matrix contained at least two kinds of proteinase, a major alkaline thiol proteinase having an optimal pH at 8.5 and a minor neutral proteinase having an optimal pH at 7.5. The major matrix proteinase activity was strongly inhibited by leupeptin, chymostatin, antipain and E64-C, an inhibitor of Ca2+-dependent thiol proteinase, while it was scarcely affected by diethylpyrocarbonate. The activity was also inhibited by DTNB and p-chloromercuribenzoate. Addition of hydrocarbon compounds such as ethylene glycol, glycerol, Triton X-100 and poly (ethylene glycol) to the reaction mixture was found to decrease the matrix proteinase activity. Neither cytochrome c nor glutamate dehydrogenase was hydrolyzed when subjected to the matrix proteinase activity in vitro. On the other hand, cytochrome c oxidase was effectively hydrolyzed, and the enzyme associated with the mitochondrial innermembrane fragments was partially hydrolyzed by the major matrix proteinase activity.

Effects of Aging and Liver Disease upon the Pharmacokinetics of Nipradilol

AbstractObjective: The effects of aging and liver disease on the pharmacokinetics of nipradilol were studied after a single oral dose of 6mg. Study Participants: Nipradilol was administered to three groups of subjects: younger healthy volunteers with a mean age of 33.2 years (group I, n = 6), older subjects without hepatic dysfunction with a mean age of 55.5 years (group II, n = 6), and patients with histologically confirmed cirrhosis of the liver with a mean age of 55.4 years (group III, n = 8). Results: When compared with younger subjects (group I), the older subjects (group II) had a significantly longer time to maximum concentration, a greater area under the plasma concentration-time curve (AUC), a greater bioavailability (F), and a greater 24-hour urinary excretion of nipradilol. There was also a tendency towards a longer half-life in group II compared with group I. Cirrhotic subjects (group III) showed the same differences relative to group I. In addition, F was significantly larger and the plasma clearance was significantly decreased in group III compared with group II. Nearly identical results were demonstrated for the pharmacokinetics of denitrated nipradilol, one of the major metabolites of the test drug. A significant correlation was demonstrated between the AUC of nipradilol and age when groups I and II were combined. Conclusion: It was concluded that the pharmacokinetics of nipradilol may be altered with aging and hepatic dysfunction, and that changes in metabolism are likely to be a major factor.