Tadashi Iso

Method for determination of angiotensin-converting enzyme activity in blood and tissue by high-performance liquid chromatography.

A simplified method for an angiotensin-converting enzyme activity assay in biological samples was developed. Samples were incubated with hippurylhistidylleucine, an artificial substrate of angiotensin-converting enzyme. The reaction was terminated by the addition of metaphosphoric acid and liberated hippuric acid in the supernatant was quantitated directly by reversed-phase high-performance liquid chromatography. Tissues were homogenized in the presence of Nonidet-P40, a detergent, and the resulting supernatant was used for the assay of tissue angiotensin-converting enzyme activity by high-performance liquid chromatography. The present procedure made it possible to determine angiotensin-converting enzyme activity in whole blood and the total activity in tissues. A comparative study of angiotensin-converting enzyme activity in plasma, kidney and lung of five experimental animals showed a high degree of variation from species to species.

Cardiovascular characterization of SD-3211, a novel benzothiazine calcium channel blocker, in isolated rabbit hearts

The cardiovascular effects of SD-3211, a novel benzothiazine Ca++ channel blocker, were compared with those of diltiazem and nicardipine in Langendorff-perfused rabbit hearts. SD-3211 was more potent in increasing coronary artery flow than in depressing cardiac function (i.e., contractile force, heart rate and conduction time). The relative specificity of SD-3211 for coronary vasodilation to cardiodepression was clearly greater than that of diltiazem, but less than that of nicardipine. Thus, the present study demonstrates that SD-3211, despite a non-dihydropyridine type of Ca++ channel blocker, can be characterized as a potent coronary vasodilator with a little effect on cardiac function.

The role of prostaglandins in experimental ocular inflammations.

Intraocular inflammations (uveitis) were produced in rabbits by intravitreal injection of killed and driedMycobacterium butyricum orE. coli endotoxin, or paracentesis of the anterior chamber. The increase in permeability of the blood-aqueous barrier and the leucocyte migration into the aqueous humor were observed after these stimuli, although the leucocyte did not migrate after paracentesis. Topically applied indomethacin reduced these inflammatory parameters in the latter two models. However, the increased permeability afterM. butyricum injection was not affected by indomethacin, though the leucocyte migration was reduced. On the other hand, prostaglandin-like substances in the aqueous humor were significantly elevated in the latter models, whereas only traces of these substances were detected in the former model. These results indicate that, unlike the increase in the permeability of the blood-aqueous barrier after endotoxin injection and paracentesis, the response afterM. butyricum injection is not mediated by prostaglandins. The role of prostaglandins in the leucocyte migration in these ocular inflammations was also discussed.

Passive Anaphylaxis in Rat Conjunctiva and Topical Effects of Antiallergic Agents. Hypersensitivity in Conjunctiva and Drug Efficacy

Homologous passive anaphylactic reaction mediated by a reaginic antibody was caused in rat conjunctiva and the effects of several drugs on this reaction were examined by estimating the leakage of dye

Effects of immunomodulators on candidacidal activity of normal peritoneal cells in BALB/c mice

Macrophages which play an important role in host resistance against infections are considered to be a target for various immunomodulators. In order to examine the effects of selected immunomodulators on macrophage function, the effects of N-(2-mercapto-2-methylpropanoyl)-L-cysteine (SA96), levamisole (LMS) and D-penicillamine (D-Pc) on the candidacidal activity of the normal peritoneal cells (PC) were investigated. In the in vitro studies, SA96 increased the candidacidal activity of PC 4-fold, while D-Pc and LMS treatments did not increase this activity. In the ex vivo studies, PC obtained from the mice pre-treated with SA96, D-Pc and LMS showed a high candidacidal activity. Elevated candidacidal activity was not due to changes of cell types of PC populations. These results suggest that D-Pc and LMS activate the function of macrophage in vivo and SA96 activates the function both in vitro and in vivo.

Potentiative effects of sulfhydryl compounds on carrageenin-induced oedema in rats and relationship to their potencies as inhibitors of angiostin-converting enzyme in vivo

Carrageenin-induced oedema in rats was potentiated by oral administration of (4R)-3-[(2S)-3-mercapto-2-methylpropanoyl]-4-thiazolidinecarboxylic acid (SA291) and related sulfhydryl compounds, and the effect was closely correlated with their potencies as inhibitors of angiotensin-converting enzyme in vivo.

Potentiating mechanism of bradykinin action on smooth muscle by sulfhydryl compounds.

(4R)-3-[(2S)-3-Mercapto-2-methylpropanoyl]-4-thiazolidinecarboxylic acid (YS-980), a potent angiotensin I (AI) converting enzyme inhibitor, inhibited the contractile response of isolated guinea-pig ileum to AI but not to AII, while it potentiated the response to bradykinin. Other sulfhydryl compuonds also produced inhibition of AI action, and the effects were closely correlated with their potentiating activities against bradykinin action. These results suggest that it is mainly inhibition of the enzyme in the tissue which participates in the mechanism of potentiation of kinin action by YS-980.

Potentiative effects of a kininase II inhibitor (YS980) on carrageenan-induced oedema in rat hind paw and roles of plasma kininogen

Bradykinin is formed from high molecular weight kininogen in plasma through activation of a kininforming enzyme, kallikrein, and is inactivated by kinindegradating enzymes, kininase I and 11. The peptide is believed to be one of important chemical mediators in carrageenan-induced inflammation. The inflammation is suppressed by cellulose sulphate and bromelain which deplete plasma kininogen (Di Rosa et al 1971 ; Katori et al 1978). Recently, we reported carrageenan oedema to be potentiated by an orally active kininase I1 (EC 3.4.15. I ) inhibitor, (4R)-3-[(2S)-3-mercapto-2-methylpropanoyl]-4-thiazolidinecarboxylic acid (YS980), and suggested that its potentiation of carrageenan oedema is due to its inhibitory action on kininase I1 in the inflamed site (Is0 et al 1978). We now report on the role of plasma kininogen in the development of potentiative effects of YS980 on carrageenan-induced oedema in rat hind paw.

Effect of tiopronin on prostaglandin synthesis in rabbit kidney medulla slices

Abstract— The effect of 2‐mercaptopropionylglycine (tiopronin), which is widely used for the treatment of various hepatic disorders, on the generation of medullary prostaglandins (PG) E2 and F2α has been examined. Tiopronin had a potent inhibitory effect on PG E2 formation. Simultaneously, PG F2α production was increased. In the presence of tiopronin the net increased amount of PG F2α was much smaller than the net decreased amount of PG E2 (6–20%). These results suggest that tiopronin has the potential to modulate PG E2 and F2α synthesis by affecting endoperoxide E2 isomerase or endoperoxide reductase and that this effect may represent some pharmacological action of the drug.

Effects of sodium loading on antihypertensive responses to an angiotensin-converting enzyme inhibitor in spontaneously hypertensive and renal hypertensive rats

Sodium loading significantly attenuated the antihypertensive potency of an angiotensin-converting enzyme inhibitor, SA446, in 2-kidney, 1-clip renal hypertensive rats, but the potency of SA446 remained unchanged in spontaneously hypertensive rats. Basal levels of plasma renin activity of both types of hypertensive rats were suppressed by sodium loading. From these results, it appeared that a different mechanism was involved in the maintenance of hypertension in 2-kidney, 1-clip renal hypertensive rats and in spontaneously hypertensive rats. It also appeared that the mechanism of the antihypertensive action of angiotensin-converting enzyme inhibitors was not explainable only by the suppression of the plasma renin-angiotensin system.