[Synthesis and cardioprotective properties of apelin-12 and its structural analogs].

The apelin-12 and a number of its analogs, resistant to degradation of proteases, were synthesized by Fmoc- method of SPPS. By-products of synthesis were examined. It was found that serine hydroxyl group was sulfating during the final deprotection of apelin-12 (I) and its analogs. Sulfate moiety of Arg-protecting group transfer into hydroxyl group of Ser. Amount of by-product depends on presence of water in cleavage mixture. Furthermore, the final deprotection of amide analogs of apelin-12 (III, IV) is closed with formation of by-product--4-hydroxybenzylamide, its amount range on 20-8% on reaction mixture accordance HPLC data and also depend on composition of cleavage mixture. Effects of the synthesized peptides on recovery of cardiac function after ischemia were examined in a model of isolated perfused rat heart. Infusions of any of the peptides (I-V) before ischemia resulted in a significant improvement of contractile and pump function recovery compared to the control. Cardioptotective efficacy of the peptides increased in the following rank (I) < (II) = (III) < (IV) = (V).

[The effect of adaptation to repeated stresses on the recovery of cardiac function and creatine phosphate after total ischemia (a 31P-NMR study)]. / Vliianie adaptatsii k povtornym stressam na vosstanovlenie funktsii serdtsa, kreatinfosfata posle total'noi ishemii (issledovanie metodom 31P-IaRM).

Adaptation to stress was produced by eight immobilizations of rats for 1 hour every other day. The effects of 25-min ischemia and subsequent 50-min reperfusion on the heart contractile function and energy metabolism were studied. In the adapted rats, the velocities of contraction and relaxation as well as the developed pressure restored during reperfusion much faster than in the controls. The NMR-study showed that a drastic fall of creatine phosphate (CP) and ATP during ischemia was followed by a rapid CP restoration, a Pi drop and a slow ATP restoration during reperfusion. In the adapted animals, the CP restoration was twice as rapid as in the controls. It is obvious that in adaptation to stress the heart function and the system of CP resynthesis appear to be significantly more resistant to ischemia stroke and this is why they restore their activity faster than in the controls.

[The determination of phospholipase activity using the 31P-NMR spectroscopic method]. / Opredelenie aktivnosti fosfolipazy s metodom 31P-IaMR spektroskopii.

The authors have developed a rather rapid and convenient method for testing and measurement of phospholipase C (EC 3.1.4.3) activity, based on continuous recording of the signal reduction in 31P-NMR spectrum of lecithin phosphate group (chemical sigma shift = 0.2 parts per million as regards H3PO4) or of phosphocholine signal augmentation (sigma = -4 parts per million). This method permits a quantitative estimation of lecithin loss or phosphocholine accrual from the kinetics of integral intensity changes in the course of an enzymic reaction and then calculate phospholipase C activity without resorting to thin-layer chromatography traditionally used for this purpose.

[Interaction of alkali metal ions with Ca2+-binding center of Ca2+- ATPase of the sarcoplasmic reticulum in skeletal muscles]. / Vzaimodeistvie ionov shchelochnykh metallov c Ca2+- sviazyvaiushchimi tsentrami Ca2+-ATPazy sarkoplazmaticheskogo retikuluma skeletnykh myshts.

Sodium ion interaction with sarcoplasmic reticulum (SR) membranes leads to considerable alterations of the [23Na]NMR lineshape. Na+ binding to SR in the presence of Ca2+ and H+ is well described by a model which postulates a competitive ion binding to high and low affinity sites of Ca2+-ATPase. The dissociation constant, Kd, for high and low affinity sites is 5 and 10 mM, respectively, for Na+ and (3-5).10(-8) and 1.5.10(-3) M, respectively, for Ca2+. The pK value for high and low affinity sites is 7.3 and 6.1, respectively. Other alkaline metal ions compete with Na+ for the low affinity sites of Ca2+-ATPase; their affinities decrease in the following order: Na+ = K+ greater than Rb+ greater than Cs greater than Li+. Some of the Na+ binding sites (approximately 10%) do not interact with Ca2+.