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1.
H Nawrath  I Blei  R Gegner 《Experientia》1980,36(1):72-74
beta-adrenoceptor stimulation by isoprenaline increases the potassium efflux in beating guinea-pig atria. This effect is not mimicked by 8-bromo-cyclic AMP, a cyclic AMP analogue which exerts a positive inotropic effect in this preparation.  相似文献   

2.
M Kohlhardt  K Haap 《Experientia》1976,32(2):150-152
Alkalosis (pH 7.8) produced by reduction of CO2 concentration augmented both upstroke velocity of Ca action potentials and isometric contractile force of mammalian heart muscle. If the increase of pH to 7.8 was achieved by a raise of HCO3 concentration (with simultaneous reduction of CO2 concentration), the positive inotropic response was not accompanied by an augmented Ca current. Obviously, the well-known positive inotropic effect of alkalosis does not only depend upon the enhancement of transmembrane Ca influx during excitation, but can be mediated alone by affecting intracellular Ca movements as well.  相似文献   

3.
N Kondo  S Shibata 《Experientia》1984,40(12):1392-1393
Verapamil, a calcium entry blocker, had a greater inhibitory effect on the positive inotropic effect of excess Ca2+ in SHR than in NWR, suggesting that the cardiac responsiveness to verapamil was enhanced in SHR.  相似文献   

4.
Summary Alkalosis (pH 7.8) produced by reduction of CO2 concentration augmented both upstroke velocity of Ca action potentials and isometric contractile force of mammalian heart muscle. If the increase of pH to 7.8 was achieved by a raise of HCO3 concentration (with simultaneous reduction of CO2 concentration), the positive inotropic response was not accompanied by an augmented Ca current. Obviously, the well-known positive inotropic effect of alkalosis does not only depend upon the enhancement of transmembrane Ca influx during excitation, but can be mediated alone by affecting intracellular Ca movements as well.  相似文献   

5.
Summary Verapamil, a calcium entry blocker, had a greater inhibitory effect on the positive inotropic effect of excess Ca2+ in SHR than in NWR, suggesting that the cardiac responsiveness to verapamil was enhanced in SHR.  相似文献   

6.
Summary -adrenoceptor stimulation by isoprenaline increases the potassium efflux in beating guinea-pig atria. This effect is not mimicked by 8-bromo-cyclic AMP, a cyclic AMP analogue which exerts a positive inotropic effect in this preparation.  相似文献   

7.
L L Protas 《Experientia》1992,48(10):1007-1009
The effect of carbachol on twitch tension of atrial preparations from chick embryos of different incubation ages (3-14 days) was studied. At every age carbachol evoked negative (at low concentrations) and positive (at higher concentrations) inotropic responses. Maximal response values for both effects increased with age; in 3- and 5-day atria the positive inotropic response prevailed. The muscarinic antagonist pirenzepine inhibited the positive (on 5-day atria) and negative (on strips of 14-day atria) inotropic effects of carbachol with pA2 values of 6.8 and 8.0, respectively, suggesting that muscarinic receptors mediating these effects belong to different receptor subtypes.  相似文献   

8.
The effect of carbachol on twitch tension of atrial preparations from chick embryos of different incubation ages (3–14 days) was studied. At every age carbachol evoked negative (at low concentrations) and positive (at higher concentrations) inotropic responses. Maximal response values for both effects increased with age; in 3- and 5-day atria the positive inotropic response prevailed. The muscarinic antagonist pirenzepine inhibited the positive (on 5-day atria) and negative (on strips of 14-day atria) inotropic effects of carbachol with pA2 values of 6.8 and 8.0, respectively, suggesting that muscarinic receptors mediating these effects belong to different receptor subtypes.  相似文献   

9.
Two new beta-adrenoceptor blocking drugs with acute antihypertensive and positive inotropic effects are described: Compound A (2-[4-(3-tert.butylamino-2-hydroxypropoxy)phenyl]-4-trifluoromethylimidazole) and MK-761 (2-(3-tert.butylamine-2-hydroxypropoxy)-3-cyanopyridine hydrochloride). In SH rats both compounds, given orally, lowered arterial pressure and were more potent than hydralazine. The antihypertensive effect of compound A but not of MK-761 was antagonized by timolol. Both compounds had positive inotropic activity on cat heart papillary muscles; these effects were antagonized by timolol. The pretreatment of animals with reserpine greatly reduced the positive inotropic effect of MK-761 but not of compound A. The acute antihypertensive and positive inotropic effects of compound A are like to be at least partially due to stimulation of beta-adrenoceptors, e.g. intrinsic sympathomimetic activity. The effects of MK-761 on the same parameters appear to be mediated by different mechanisms.  相似文献   

10.
Summary In dogs anæsthetized with morphine-chloralosane, the cerebral ventricles are perfused with artificial solutions. After having been warmed up to body temperature, these solutions are allowed to flow into a lateral ventricle by a needle inserted laterally through the skull, the outflow taking place through a second needle placed suboccipitally in the cisterna. An excess of potassium in the cerebral ventricles increases the vasomotor tonus and the vasomotor responses produced by faradization of the central end of the vagus in the neck and by changing the pressure in the isolated carotid sinuses. An excess of calcium depresses the tonus of the vasomotor center and its reflex responses. An excess of calcium may be neutralized by an excess of potassium. Perfusion with a solution containing no calcium increases the tonus and the responses of the vasomotor center, while the absence of potassium does not seem to have any influence on the vasomotor system. A solution without potassium and calcium produces an increase of the tonus and the responses of the vasomotor center, these effects being due to the absence of calcium.  相似文献   

11.
Summary The present results show that the sensitivity of the chick myocardium to the positive motropic effect of Ca++ decreases during development and that the Ca++ concentration of the physiological solution used must be lowered below normal to study the effects of positive inotropic agents in preparations from younger embryos. Isoproterenol elicits positive inotropic responses in 7–9-day embryonic ventricle and in newborn chick atria; however, the 4-day embryonic myocardium is unresponsive to isoproterenol.This work was supported by Grant No. HL-15995 from the National Heart Institute (USPHS).The authors would like to thank Dr.F. E. Shideman for the isolated tissue baths used in these experiments.  相似文献   

12.
Summary Two new-adrenoceptor blocking drugs with acute antihypertensive and positive inotropic effects are described: Compound A (2-[4-(3-tert. butylamino-2-hydroxypropoxy)phenyl]-4-trifluoromethylimidazole) and MK-761 (2-(3-tert. butylamino-2-hydroxypropoxy)-3-cyanopyridine hydrochloride). In SH rats both compounds, given orally, lowered arterial pressure and were more potent than hydralazine. The antihypertensive effect of compound A but not of MK-761 was antagonized by timolol. Both compounds had positive inotropic activity on cat heart papillary muscles; these effects were antagonized by timolol. The pretreatment of animals with reserpine greatly reduced the positive inotropic effect of MK-761 but not of compound A. The acute antihypertensive and positive inotropic effects of compound A are likely to be at least partially due to stimulation of-adrenoceptors, e.g. intrinsic sympathomimetic activity. The effects of MK-761 on the same parameters appear to be mediated by different mechanisms.  相似文献   

13.
G Coruzzi  E Poli  F Fesani  D Medici  G Bertaccini 《Experientia》1983,39(11):1284-1286
H2-Receptor antagonists were found to possess in various degrees a negative inotropic effect on human atria in vitro. This effect seemed to be independent of H2-receptor blockade and, at least in the case of oxmetidine, seemed to involve calcium ion transport and/or utilization.  相似文献   

14.
Summary The denervated diaphragm of the rat possesses a lower calcium concentration and dry weight than the non-denervated muscle. Decrease of [Ca]e causes a faster rise and fall of the K-contracture in the non-denervated diaphragm of the rat. Increase of [Ca]e has the reverse effect. The behaviour of the denervated muscle is different. TEA and carbachol influence the potassium contracture in almost the opposite way.  相似文献   

15.
Summary Potassium and sodium from isolated pig hypothalamic vesicles cause a dose dependent release of noradrenaline. The releasing effect of nicotine is less pronounced than that of acetylcholine. No addition of the effects could be observed by simultaneous incubation with calcium and potassium or calcium and nicotine. The effect of potassium is abolished by tetracain.

Ausgeführt mit Unterstützung der Deutschen Forschungsgemeinschaft.  相似文献   

16.
The mechanism of the positive inotropic effect of prostacyclin (PGI2) (2.6×10?6 mol/l) on the isolated right ventricle of rat heart was studied. Our results show that the positive inotropic effect of prostacyclin is produced indirectly through beta adrenoceptors and slow Ca2+ channels, because blockade of slow Ca2+ channels with verapamil (10?6 mol/l) and beta adrenoceptors with propranolol (10?6 mol/l) abolishes this effect. Alpha adrenoceptors do not mediate the action of PGI2.  相似文献   

17.
Summary The effect of alterations of dietary potassium intake on the plasma concentration and the urinary excretion of vasopressin was studied in male rats. Ingestion of a high potassium diet resulted in increases in the plasma concentrations of potassium and vasopressin, systolic blood pressure, urine flow, and urinary vasopressin excretion. Ingestion of a low potassium diet had little effect on the plasma vasopressin concentration and systolic blood pressure but caused decreases in the plasma potassium concentration and urinary vasopressin excretion. The results indicate that physiological changes in the plasma potassium concentration or some other consequence of altered dietary potassium intake can affect vasopressin release and excretion.  相似文献   

18.
The effect of alterations of dietary potassium intake on the plasma concentration and the urinary excretion of vasopressin was studied in male rats. Ingestion of a high potassium diet resulted in increases in the plasma concentrations of potassium and vasopressin, systolic blood pressure, urine flow, and urinary vasopressin excretion. Ingestion of a low potassium diet had little effect on the plasma vasopressin concentration and systolic blood pressure but caused decreases in the plasma potassium concentration and urinary vasopressin excretion. The results indicate that physiological changes in the plasma potassium concentration or some other consequence of altered dietary potassium intake can affect vasopressin release and excretion.  相似文献   

19.
Crown ethers which influence cardiac and respiratory muscle contractility   总被引:1,自引:0,他引:1  
Guinea-pig tracheal smooth muscle and heart muscle demonstrated a variety of in vitro positive and negative inotropic responses to concentrations of crown ethers in the nmole/1 to mumole/1 range. It is suggested that these ionophoretic compounds have potential as therapeutic agents.  相似文献   

20.
Summary For therapeutic heart-equieffective concentrations of 15 genins, there is a correlation between the inhibition of the sodium transport in cold-stored red cells of man and the positive inotropic action on the isolated auricle preparation of the guinea pig, damaged by phenylbutazone.  相似文献   

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