Reiko Shiba

Elimination of Intravenously Injected Endothelin-1 from the Circulation of the Rat

Summary The rate of elimination and the fate of endothelin-1 (ET-1) from the circulating blood was studied in urethane-anesthetized rats by intravenous injection of [125I]-labeled ET-1. The vasoconstrictor activities of the iodinated ET-1 were confirmed to be similar to those of native ET-1. Following i.v. bolus injection of 30 pmol/kg of [125I]-ET-1 into the femoral vein, the total radioactivity of the right atrial blood decayed rapidly, with a half-life of 7 min. At 5 min after the injection, the administered radioactivity distributed chiefly to the parenchyma of the lungs, kidneys, and liver. The analysis of the chemical form of labeled peptides from the plasma by reverse-phase high-performance liquid chromatography (HPLC) demonstrated no appreciable amount of degraded forms of [125I]-ET-1 in the blood for up to 60 min. [125I]-ET-1 was also stable for up to 60 min upon incubation in vitro with heparinized rat blood at 37

Vasoconstrictor response of large cerebral arteries of cats to endothelin, an endothelium-derived vasoactive peptide

C. Even when the same amount of labeled ET-1 was injected together with a pressor dose (1,500 pmol/kg) of cold ET-1, the half-life of the radioactivity in the bloodstream was exactly identical to that for [125I]-ET-1 alone. Nevertheless, the pressor response continued for more than 90 min after i.v. bolus injection of 1500 pmol/kg of ET-1 to the rat. These results clearly indicate that the elimination of ET-1 from circulating blood and the ET-1-induced pressor response are not in parallel, and the relatively rapid disappearance of ET-1 from the bloodstream is mostly due to the removal of the peptide by the parenchymal tissues, in the anesthetized rat. The long-lasting pressor action of ET-1 may be ascribed to our previous finding that the dissociation of ET-1 from its specific binding sites on vascular smooth muscle cells is extremely slow.

Cloning and expression of rat preproendothelin-3 cDNA

Endothelin, a recently discovered endothelium-derived peptide, has been reported to produce potent vasoconstriction in various vessels of experimental animals. To study the involvement of endothelin in the regulation of vascular tonus in humans, isolated human mesenteric arteries were investigated by both pharmacological and immunohistochemical methods. The vasoconstrictor action of endothelin-1 was examined on ring segments of human mesenteric arteries. Endothelin-1 induced a slowly developing and sustained contraction, with an EC50 value (half-maximal effective concentration) of 2.9 x 10(-9) M, two orders of magnitude smaller than that of norepinephrine (EC50 of 3.9 x 10(-7) M), indicating that the vasoconstrictor action of endothelin-1 is about 100 times more potent than that of norepinephrine. The contractile effect of endothelin-1 was affected neither by adrenergic, cholinergic, histaminergic, nor serotonergic antagonists, nor by inhibitors of arachidonic acid metabolism. The vasoconstrictor response to endothelin-1 was effectively antagonized by nicardipine, a dihydropyridine Ca2+ channel blocker. Endothelin-1 profoundly augmented contractile response to Ca2+ in partially depolarized tissues. Immunohistochemical studies revealed for the first time that endothelin-like immunoreactivity was localized in endothelial cells of human mesenteric artery. The results of the present study indicate that endothelin-1 is one of the most potent vasoconstrictors in the human mesenteric artery and that it induces vasoconstriction via an ultimately accelerating Ca2+ influx through voltage-dependent Ca2+ channels. Since endothelin-1 can be located in human endothelial cells, it may play an important physiological or pathophysiological role.

Endothelins: vasoconstrictor effects and localization in canine cerebral arteries

Endothelin, a 21-amino acid peptide produced by vascular endothelial cells, caused a sustained constriction of isolated large cerebral arteries of cats in a dose-dependent manner. The increased tone of the tissue did not return to the resting level after repeated washings. No vasodilator response was evoked by endothelin in the presence of an active tone. The contractile response of cerebral arteries was not inhibited by rubbing of the endothelium, cold storage denervation or indomethacin. In contrast, nicardipine or diltiazem antagonized the endothelin-induced contraction non-competitively. No contraction was evoked by endothelin in a Ca2+-free solution while the addition of Ca2+ ions in the presence of endothelin in a Ca2+-free solution caused a sustained contraction. Ca2+-induced contraction in the Ca2+-free solution containing endothelin was also inhibited by nicardipine. Therefore, endothelin causes a direct contraction of the smooth muscles of cat cerebral arteries, probably by activating the influx of Ca2+ ions through L-type Ca2+ channels of smooth muscles.

Hydrogen peroxide-induced cellular injury is associated with increase in endogenous fluorescence from rat gastric mucosal epithelial cell culture: A new method for detecting oxidative cellular injury by fluorescence measurement

We report here the cloning and expression of a rat full-length cDNA encoding preproendothelin-3 (preproET-3). The predicted rat preproET-3 consisted of 167 amino acid residues. As in other ET-family peptides, the mature rat ET-3 was predicted to be produced through unusual processing from a 41-residue intermediate, the big ET-3 in rat. Transient transfection of COS-7 cells with the cloned preproET-3 cDNA resulted in the production of mature ET-3 and this production was inhibited by phosphoramidon, a metaloprotease inhibitor. This suggested that a phosphoramidon sensitive mechanism was involved in the production of ET-3 in the transfected COS-7 cells. Northern blot analysis showed that an approximately 3.0-kb rat preproET-3 mRNA was expressed in rat tissues, including the eye ball, submandibular gland, brain, kidney, jejunum, stomach and spleen. A 2.0-kb and a 3.3-kb mRNA were also detected in the eye ball and small intestine, respectively. The distinct distribution of rat preproET-3 mRNA from that of preproET-1 mRNA suggested that ET-1 and ET-3 played different roles.

Diclofenac-induced gastric mucosal fluorescence in rats.

1 The vascular effects of endothelin and localization of endothelin‐like immunoreactivity were characterized in isolated cerebral arteries of dogs. 2 Endothelin‐like immunoreactivity was detected in a few populations of endothelial cells of dog basilar artery. 3 Endothelin‐1, endothelin‐2 and endothelin‐3 contracted isolated ring preparations of cerebral arteries in a dose‐dependent manner independently of the presence of endothelium. The ED50 values (and 95% confidence intervals) for the contraction were 411 pm (242–697 pm) and 478 pm (295–776 pm) for endothelin‐1 and endothelin‐2, respectively. Endothelin‐3 induced vascular contraction at a higher concentration (ED50 = 26.5 nm, 95% confidence interval = 15.7–45.7 nm). 4 The increases in tone induced by endothelin‐1 and endothelin‐2 did not return to the resting level after repeated washings, while a rinse with Krebs solution reversed the vasoconstrictor response to endothelin‐3. The endothelins did not cause any vasodilator response in arteries precontracted with uridine 5′‐triphosphate even in the presence of intact endothelial cells. 5 NiCl2 (1 mm) attenuated the contractions induced by endothelin‐3 (10–300 nm) and those to relatively low doses (1 nm) but not higher doses (10–100 nm) of endothelin‐1 and endothelin‐2. The contractions in response to endothelin‐1, endothelin‐2 and endothelin‐3 were greatly attenuated in Ca2+‐free solutions although high concentrations of endothelin‐1 and endothelin‐2 still evoked contractions. 6 These results suggest that the vasoconstriction induced by endothelin‐3 and lower doses of endothelin‐1 and endothelin‐2, largely depends on the influx of Ca2+ ions. The apparent insensitivity to Ni2+ shows that additional distinct mechanisms also operate in the vasoconstrictor responses to high concentrations of endothelin‐1 and endothelin‐2. 7 The presence of endothelin‐like immunoreactivity in endothelial cells suggests that endothelin is a potential endogenous spasmogen.

High Rate of Induction of Human Autologous Cytotoxic T Lymphocytes against Renal Carcinoma Cells Cultured with an Interleukin Cocktail

Abstract: To develop a new method of detecting cellular injury caused by oxygen radicals, we studied endogenous fluorescence from the cultured cells of a rat gastric mucosal epithelial cell line. Measurement with an ultra-high sensitivity camera-image processor system under an inverted epifluorescence microscope showed that the fluorescence intensity of the cells increased time- and dose-dependently after the addition of hydrogen peroxide (H2O2), an oxygen radical precursor, to the medium. This increase was inhibited by the presence of catalase. Phase-contrast and fluorescence microscopy revealed that the fluorescence was emitted from granular substances in the cytoplasm of the injured cells. The spectral pattern of excitation and emission indicated that the fluorescent substances were flavins. In cell-free experiments, glutathione reductase which has flavin adenine dinucleotide (FAD) at the active site, increased in fluorescence after incubation with H2O2 in the presence of reduced glutathione and glutathione peroxidase. These findings indicate that FAD in the cytoplasm of cells injured by H2O2 increased in endogenous fluorescence according to the extent of injury, and suggest that fluorescence measurement may be a simple method in cellular toxicology to detect oxygen radical-induced injuries.

Direct detection of hepatitis B virus gene integrated in the Alexander cell using fluorescence in situ polymerase chain reaction

We previously reported that the gastric mucosa emits fluorescence of porphyrins at the onset of gastric lesions induced by hemorrhagic shock. In this study, we investigated whether the fluorescent substance concerns with the gastric mucosal injuries induced by diflofenac, a nonsteroidal antiinflammatory drug (NSAID). In the gastric mucosa treated with diclofenac, lesions were generated and myeloperoxidase activity increased. Diclofenac administration also increased thiobarbituric acid-reactive substances, a index of tissue peroxidation. After diclofenac treatment, the gastric mucosal fluorescence intensities rose. HPLC analysis demonstrated that the fluorescent substances were mesoporphyrin and protoporphyrin, which were the same as found in hemorrhagic shock. Pretreatment of the tissue with radical scavenging substances, catalase and troxipide, restrained the increase of mucosal fluorescence intensity, tissue peroxidation, and lesion formation. These findings indicate that diclofenac treatment induced the generation of porphyrins as well as tissue peroxidation in gastric mucosal tissue. This study suggests that autofluorescence observation is a useful tool to identify diclofenac-induced gastric injury.

Characterization of the effect of endothelins in canine cerebral arteries

A high rate of induction (9 of 10 cases) of human autologous cytotoxic T lymphocytes (CTL) was achieved in vitro from peripheral blood mononuclear cells of renal carcinoma patients by applying an interleukin (IL)‐cocktail consisting of IL‐1, ‐2, ‐4, and ‐6. The CTL specifically lysed their own target carcinoma cells within 24 h but did not kill neighboring autologous normal kidney cells or allogeneic renal cancer cell lines. In the case of TUHR4TKB, for which autologous CTL were not induced, no expression of MHC class‐I molecules was observed on the surface of these carcinoma cells, although they were sensitive to autologous natural killer cells. The results imply that adoptive immunotherapy for metastasized renal carcinoma will be feasible with autologous CTL in combination with natural killer cells.