[The comparative efficacy of emoxipine and sodium oxybutyrate in experimental myocardial ischemia]. / Sravnitel'naia éffektivnost' émoksipina i oksibutirata natriia pri eksperimental'noi ishemii miokarda.

The efficacy of emoxypine (2-ethyl-6-methyl-3-hydroxypyridine chlorohydrate) versus sodium hydroxybutyrate in total and local ischemia followed by reperfusion was studied in the experiments on rat isolated hearts. Emoxypine in a dose of 1 nM in total ischemia was shown to have a protective action, by decreasing reperfusion contracture. In local ischemia, emoxypine, unlike sodium hydroxybutyrate, did not favour greater restoration of the amplitude of isolated heart contractions, but restored coronary flow and stabilized contraction frequency better than did sodium hydroxybutyrate.

[Milrinone decreases the positive inotropic response of heart muscle to izadrin]. / Milrinon snizhaet polozhitel'nyi inotropnyi otvet serdechnoi myshtsy na izadrin.

The interaction of the cAMP-phosphodiesterase inhibitor milrinone and the beta-adrenoceptor agonist isoproterenol was studied on guinea-pig isolated hearts. Milrinone, (10 microns) caused a positive inotropic response which differed from that of isoproterenol (7 nM) and decreased cardiac inotropic responses to the subsequent administration of isadrin despite a significant great rise in cAMP. The interaction of the drugs is assumed to be associated with the milrinone-induced increase in cGMP which is able to restrict myocardial cAMP-activated processes.

[Cardiac contractile function following acute cooling of the body and the adaptogenic correction of its disorders]. / Sokratitel'naia funktsiia serdtsa posle ostrogo okhlazheniia organizma i adaptogennaia korrektsiia ee narushenii.

In experiments on white Wistar rats the effect of acute 4-hour freezing at -10 degrees C on contractile function of the hearts isolated by the Langendorff technique, and the protective efficacy of Rhodiola rosea extract were investigated. The obtained results testify to the fact that acute cooling leads to a decrease in myocardial contractile activity that recovers during 18 hours. But this recovery cannot be complete as it does not result in stable contractility of isolated heart in perfusion. Preliminary adaptation of animals during treatment with Rhodiola rosea extract prevents the decrease in contractility force immediately after acute cooling and contributes to the stable contractility during 60 minutes of perfusion. Moreover, Rhodiola rosea extract does not remove the disturbance in diastolic function and in all cases leads to a decrease in coronary blood flow. The effect of Rhodiola rosea extract on the myocardium is likely to be similar to that of myocardial recovery after acute cooling.

[The role of cyclic AMP and cyclic GMP in realizing an inotropic effect of verapamil on the heart muscle]. / Rol' tsAMF i tsGMF v realizatsii inotropnogo deistviia verapamila na serdechnuiu myshtsu.

The effect of verapamil on dynamics of cAMP and cGMP was studied during the single heart cycle using the isolated perfused guinea pig heart activated by isoproterenol. The changes of cyclic nucleotides were Ca(2+)-dependent; verapamil altered the cAMP and, to a lesser extent, the cGMP dynamics in the myocardium apparently by means of shifts in homeostasis of Ca2+ in cardiomyocytes. Importance of cyclic nucleotides and their interaction in realization of the inotropic effect of verapamil are discussed.

[The action of fenoptin on cAMP dynamics in the isolated guinea pig heart during contraction-relaxation]. / Deistvie fenoptina na dinamiku tsAMF v izolirovannym serdtse morskoi svinki v protsesse ee sokrasheniia--rasslebleniia.

The influence of finoptin and Ca2+ concentration decrease on cAMP dynamic during cardiac cycle in guinea pig isolated heart, activated by isadrin (3 x 10(-8) M), has been studied. In isadrin activation of adrenoceptors cAMP concentration increased by 50% during contraction and decreased during relaxation. Hypocalcium solution (0.15 mM) and finoptin decreased cAMP concentration and influenced its dynamic during cardiac cycle.

[The effect of obzidan, finoptin and Ca2+ on the cAMP level during contraction-relaxation of isolated heart of guinea pigs activated with isadrin]. / Deistvie obzidana, finoptina i Ca2+ na soderzhanie cAMP v protsesse sokrashcheniia-rasslableniia izolirovannogo serdtsa morskoi svinki, aktivirovannogo izadrinom.

The beta-adrenoceptor blockade, slow inward calcium current blockade and calcium concentration decrease in perfusion solution were studied for their effect on cAMP oscillations during cardiac cycle in the isadrin-activated isolated heart of guinea pig. Isadrin activation (3 X 10(-8) M) of beta-adrenoceptors caused an increase of the cAMP concentration by 50% during the contraction. All the actions decreased an average level of cyclonucleotide in the myocardium as compared with isadrin and what is more, obsidan (10(-6) M) removed the cAMP oscillations almost completely, the hypocalcium solution (0.15 mM Ca2+) decreased their amplitude and duration, finoptin (3 X 10(-8) M) qualitatively changed the oscillation profile. The results obtained make it possible to suggest, that a change in the concentration of ionized calcium in myoplasma is one of the reasons inducing changes in the cAMP during the cardiac cycle.