Nucleotide receptors in hepatic stellate cells of the rat

AbstractWhen hepatic stellate cells were stimulated by UTP, ATP, or ADP, cellular levels of inositol phosphates significantly increased (UTP > ATP > ADP > 5′-O-(3-thiotriphosphate). Thirty min after incubation with 100 μM of UTP, ATP, or ADP, levels of inositol monophosphate increased to 1318 ± 116, 616 ± 87 and 591 ± 234% of control levels, respectively, with concomitant increase in the production of inositol trisphosphate and bisphosphate. These nucleotides transiently increased the [Ca2+]i of fura-2-loaded stellate cells. Moreover, UTP, ATP, ADP and adenosine 5′-O-(3-thiotriphosphate) were able to induce contraction of stellate cells as detected using the silicone-rubber membrane method. These results suggested that hepatic stellate cells have nucleotide receptors which react predominantly with extracellular UTP and ATP and trigger the receptormediated contraction of the cells

Effect of Obstructive Jaundice and Nitric Oxide on the Profiles of Intestinal Bacterial Flora in Wild and iNOS−/− Mice

We previously reported that the plasma level of endotoxin and colonic expression of IgA in the mouse increased with obstructive jaundice induced by bile duct ligation (BDL). To elucidate the mechanism of the BDL-induced increase, we analyzed the effect of BDL on intestinal flora in wild type and inducible nitric oxide synthase (iNOS)-deficient mice (iNOS−/−) using the terminal restriction fragment length polymorphism analysis (T-RFLP) and 16S rDNA clone libraries. The amounts of bacterial DNA detected in fecal samples from both animal groups pretreated with antibiotics were extremely low as compared with untreated groups. We found that the profiles of enteric bacteria changed markedly after BDL. The bacterial composition is significantly different between not only wild type and iNOS−/− mice but also those before and after BDL, respectively. Among enteric bacteria examined, Lactobacillus murinus was found to increase markedly after BDL in rectum of both animal groups. However, Escherichia coli markedly increased after BDL in the iNOS−/− mice. These findings suggest that profiles of enteric flora change markedly in animals during obstructive jaundice by some mechanism that is affected by bile constituents and iNOS-derived NO

Fasting Differentially Modulates the Immunological System: Its Mechanism and Sex Difference

The immunological properties and hormonal metabolism in rodents are affected by physical and psychological stress more strongly in males than in females. To elucidate the mechanism and physiological significance of the sex difference in the susceptibility of animal to stresses, changes in the immunological system in plasma and intestine and hormonal status in plasma were compared among 8-week-old male and female ICR mice before and after fasting. During the fasting of animals, the expression of immunoglobulin A in intestinal mucosa, and cortisol, interleukin-10 and interferon-γ in plasma increased. These changes occurred more apparently in males than in females. Under identical conditions, the plasma levels of testosterone decreased markedly with concomitant occurrence of apoptosis in the testis, while the plasma levels of estradiol decreased calmly, and no appreciable apoptosis occurred in the ovary. These results indicate that testosterone enhances the stress-induced modulation of the immune system by some mechanism that was antagonized by estradiol

Mechanism of furosemide resistance in analbuminemic rats and hypoalbuminemic patients

Mechanism of furosemide resistance in analbuminemic rats and hypoalbuminemic patients. To elucidate the mechanism of resistance of hypoalbuminemic patients to furosemide, the effect of this diuretic on urine volume of normal and analbuminemic rats (NAR) and of hypoalbuminemic patients was studied. Intravenous administration of furosemide rapidly enhanced sodium diuresis in normal rats but not in NAR. Total plasma clearance and distribution volume of furosemide were much larger in NAR than in normal rats, while no significant difference in these pharmacokinetic parameters was observed for the unbound fraction of the diuretic between the two animal groups. In contrast, urinary secretion of furosemide was significantly lower in NAR than in normal rats. Injected furosemide bound to albumin markedly promoted diuresis in NAR, while the same dose of albumin alone had no effect, indicating that binding to albumin is essential for the delivery of furosemide to the kidney, the site for its action. Injection of the complex rapidly increased the urine volume of hypoalbuminemic patients who showed a marked resistance to this diuretic. Thus, the resistance to furosemide in both NAR and hypoalbuminemic patients may be explained on the same basis

Flow Cytometric Analysis of Ca2+-Induced Membrane Permeability Transition of Isolated Rat Liver Mitochondria

The membrane permeability transition (MPT) of mitochondria plays an important role in the mechanism of apoptotic cell death in various cells. Classic type MPT is induced by Ca2+ in the presence of inorganic phosphate and respiratory substrate, and is characterized by various events including generation of reactive oxygen species (ROS), membrane depolarization, swelling, release of Ca2+ and high sensitivity to cyclosporine A. However, the sequence of these events and the effect of antioxidants on their events remain obscure. Flow cytometry is a convenient method to investigate the order of events among various functions occurring in MPT using a limited amount of mitochondria (200 µl of 0.02 mg protein/ml) without contamination by other organelles. Flow cytometric analysis revealed that Ca2+ sequentially induced ROS generation, depolarization, swelling and Ca2+ release in mitochondria by a cyclosporine A-inhibitable mechanism. These results were supported by the finding that Ca2+-induced MPT was inhibited by antioxidants, such as glutathione and N-acetylcysteine. It was also revealed that various inhibitors of Ca2+-induced phospholipase A2 suppressed all of the events associated with Ca2+-induced MPT. These results suggested that ROS generation and phospholipase A2 activation by Ca2+ underlie the mechanism of the initiation of MPT