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Biomedical subjects

Y Katano

Publications and source records attributed to Y Katano.

At least 73 records · Page 4Linked to original sources
PubMed1983

The effects of dipyridamole on TXA2 formation by horse platelet microsomes.

The effects of dipyridamole on thromboxane A2 formation by horse platelet microsomes were studied in comparison with those of imidazole, a prototype inhibitor of TXA2 synthetase and nifedipine, a calcium antagonistic vasodilator. Thromboxane A2 was synthesized by incubating PGH2 with horse platelet microsomes and was assayed on the superfused rabbit aorta. Dipyridamole induced as strong an inhibition of TXA2 synthesis as imidazole, while nifedipine was without effects. The possible beneficial clinical outcomes of this effect of dipyridamole are discussed.

Animals↗
PubMed1980

Effects of piridoxilate, a glyoxylic acid derivative, on the energy metabolism of the heart.

Piridoxilate is a conjugation product of pyridoxine and glyoxylic acid, which may be a physiological regulator of cell respiration. Effects of this substance on the oxidation-reduction state of the pyridine nucleotides in the heart were studied using the canine heart-lung preparation supported by a donor dog. The oxidation-reduction state of the heart was estimated using the following 2 parameters: 1) myocardial redox potential and 2) NADH fluorescence in the heart muscle. In doses above 0.4 mM, piridoxilate produced a marked shift to more positive values of the myocardial redox potential and a decrease in NADH fluorescence. In contrast, ventilation of the animal with N2 gas and infusion of NaCN into the preparation resulted in a shift to more negative values of myocardial redox potential and an increase in NADH fluoresecence of the heart muscle. After pretreatment of the preparation with piridoxilate, the depression of redox potential and the increase in NADH fluorescence produced by N2 gas inhalation or by NaCN infusion were clearly reduced. These findings suggest a protective action of piridoxilate against hypoxia which may be attributable to rearrangement of the myocardial metabolism.

Animals↗
PubMed1980

[Using the isolated atrial preparation of the guinea-pig and the canine heart lung preparation (HLP) supported by a donor, the effects of guanfacine on the heart, coronary circulation and myocardial energy metabolism were studied and compared with those of clonidine (author's transl)].

In the isolated left atria of the guinea-pig, guanfacine and clonidine (10(-8)--3 x 10(-5) g/ml) produced positive inotropic effects, which were inhibited by tripelennamine, metiamide and propranolol. Up to the concentration of 10(-6) g/ml of these compounds the effects were also inhibited by phentolamine. In the isolated right atria, guanfacine in concentrations over 3 x 10(-6) g/ml, produced a negative, and clonidine, a positive chronotropic effect. Whereas the effect of clonidine was antagonized by metiamide, the effect of guanfacine was not antagonized by any blocking agents we used. In spontaneously beating right atria, the positive inotropic effects induced by guanfacine (10(-8)--10(-5) g/ml) were inhibited by propranolol or tripelennamine, while those of clonidine (10(-8)--10(-4) g/ml) were antagonized by metiamide. In canine HLP, both drugs produced a decrease in the coronary flow which was associated with a slight rise in the right atrial pressure. These effects were inhibited by phentolamine. Both drugs produced a slight decrease in the myocardial O2 consumption and an improvement of the myocardial redox potential.

Animals↗
PubMed1979

Effects of 2-nicotinamidoethyl nitrate on the cardiovascular system.

Using the dog as experimental animal, effects on the cardiovascular system of a new vasodilator, 2-nicotinamidoethyl nitrate (SG-75), were studied. In the heart-lung preparation, the compound produced a dose-dependent increase in the coronary blood flow, which was associated with only a minimal increase in the myocardial oxygen consumption. There was essentially no change in the myocardial function. The myocardial redox potential was shifted to more positive values. In the isolated perfused heart preparation (Langendorff's preparation), SG-75 produced a dilatation of only the small resistive arterioles. However, it produced a dilatation of the large conductive artery in underperfused myocardium. SG-75 produced a significant increase in the cerebral venous outflow, associated with an increase in the cerebro-spinal fluid pressure. It produced a reducation of the venous return, which was especially prominent in the lower half of the body. In the isolated smooth muscle preparation of the coronary artery, high-doses of SG-75 induced calcium antagonistic effects and produced a relaxation of the lanthanum contracture.

Animals↗
PubMed1979

Effects of niludipine (Bay a 7168) on the cardiovascular system with a note on its calcium-antagonistic effects.

1,4-Dihydro-2,6-dimethyl-4-(3-nitrophenyl)-3,5-pyridinedicarboxylic acid-bis-(2-propoxyethyl)-ester (niludipine, Bay a 7168), a newly synthesized vasodilator, was three to ten times more potent than nifedipine in dilating the coronary artery of the canine heart-lung and isolated fibrillating heart preparations, but had weaker direct cardiac depressant effects. This drug had a strong and highly selective calcium antagonistic effect on the smooth muscle and also had stronger vasodilating activity on renal and femoral vascular beds as compared to nifedipine. It inhibited myocardial oxidative metabolism in canine and guinea pig hearts.

Animals↗
PubMed1978

[Alpha- and beta-adrenoceptor blocking actions of labetalol and effects on the myocardial function, coronary circulation and myocardial energy metabolism thereof (author's transl)].

In the isolated atria, trachea and aorta of the guinea pig and in the heart-lung preparation (HLP) of the dog, labetalol was 3.6 approximately 5.9 times less potent than phentolamine in blocking alpha-adrenoceptors, 1.4 approximately 3.6 times less potent as beta 1-blocker and 6 times less potent as beta 2-blocker than propranolol. Beta 1 and beta 2-blocking actions were 12 approximately 28 and 7 times more potent than alpha-blocking action, respectively. As regards beta 1-blockade, attenuation of the heart rate increase was more prominent than that of the augmentation of the contractile force. Both in the isolated atrial preparation of the guinea pig and in canine HLP, labetalol produced a positive inotropic and chronotropic effect and a slight increase in the coronary flow associated with a slight increase in the myocardial O2 consumption and improvement of the myocardial redox potential. Myocardial extraction and usage of lactate, pyruvate and glucose tended to be decreased and those of FFA decreased significantly. The positive inotropic and chrontropic effect was observed in HLP of 6-hydroxydopamine-pretreated dogs and was abolished with propranolol. Labetalol produced a relaxation of the isolated trachea of the guinea pig, which was inhibited with propranolol. In doses higher than those required for alpha- and beta-adrenoceptor blockade, labetalol produced calcium-antagonistic action.

Adrenergic alpha-Antagonists↗
PubMed1977

[Effects of a new adrenergic beta-blocking agent, Kö 1400 on the canine heart-lung preparation supported by a donor dog and the perfused hindlimb preparation of the dog (author's transl)].

Using the canine heart-lung preparation supported by a donor, effects of a new adrenergic beta-blocking agent, dl-1-(tert. butylamino)-3-[ (2-propinyloxy) phenoxy]-2-propanol hydrochloride (Kö 1400), on cardiac function, myocardial metabolism, and coronary circulation were studied and compared with those of propranolol. Effects of this substance on the peripheral vascular bed were also studied in the perfused hindlimb preparation of the dog. Kö 1400 produced a positive inotropic and chronotropic effect. Mechanical efficiency of the heart improved after Kö 1400, while it lessened after propranolol. A decrease in the coronary flow was observed in association with a slight increase in myocardial O2 consumption, indicating that the substance exerted a direct constrictive effect on the coronary vasculature. As a beta-blocker, Kö 1400 was found to be 2-3 times more effective than propranolol. The uptake of the free fatty acid (FFA) by the heart was increased by Kö 1400 and the myocardial redox potential improved. In the perfused hindlimb preparation, intraarterial injection of Kö 1400 resulted in a transient increase of the femoral blood flow for a decrease in the flow followed by a sustained decrease. With repeated administration a marked tachyphylaxis was observed.

Adrenergic beta-Antagonists↗
PubMed1977

[Experimental studies concerning the hemodynamic and metabolic functions in the canine heart-lung preparation supported by a donor (author's transl)].

In the usual canine heart-lung preparation the coronary blood flow does not remain constant, but increases steadily ; usually, at the moment of the set up of the preparation the coronary blood flow was about 20 ml/min/100 g heart. However, in the course of 2 approximately 3 hours it becomes more than 150 ml/min/100 g heart and the responsiveness of the coronary artery is completely lost under this condition. Concurrently with the increase in the coronary flow, cardiac functions tend to deteriorate. In order to eliminate those experimental disadvantages, we added a donor dog to the heart-lung preparation. It was found that the support by the donor dog resulted in the complete improvement of the above-mentioned deterioration ; the coronary circulation (coronary blood flow and coronary artery and sinus blood oxygen saturation), cardiac function (cardiac output, right atrial pressure, heart rate and others) and cardiac metabolism (myocardial oxygen consumption, mycardial redox potential and others) were kept constant at a favorable state for more than 10 hours.

Animals↗