[Na+, K(+)-ATPase, endogenous cardiotonic steroids and their transducing role].

Na+, K(+)-ATPase--a protein complex of plasmatic membrane, which performs the dual function: firstly, it supports the Na+ and K+ homeostasis, and also transmembrane potential gradient, secondly, it serves as the transducer of signals and as the regulator of the expression of many key genes. Endogenous cardiotonic steroids, which are synthesized in the adrenal glands and hypothalamus, serve as the signal molecules. New concepts about the mechanisms of the realization of the Na+, K(+)-ATPase signal function and their connection with cellular functions, apoptosis, and with pathologies of cardiovascular system and water-salt homeostasis are described in the survey.

[Comparative study of in vitro and in vivo effect of ouabain and calixarene C107 on Na+,K(+)-ATPase activity in plasma membranes of rat hepatocytes].

The comparative study of influence of ouabain and calixarene C107, and the structure component of this calixarene--fragment M3, in the conditions of in vitro and chronic action in vivo on Na+, K(+)-ATPase activity was carried out on the fractions of plasmatic membranes (PM) of the rat hepatocytes. A general property in the conditions in vitro is the ability of calixarene C107 and ouabain (both substances were in the concentration of 1 mM) to inhibit PM Na+, K(+)-ATPase of rat hepatocytes. However, in the case of activities of calixarene C107 and ouabain in the conditions in vivo heterogeneous action on Mg2(+)-ATPase and Mg2+, Na+, K(+)-ATPase activities takes place: total activity in the conditions of injection of increased concentrations of ouabain remains without changes, but Mg2(+)-ATPase activity significantly grows; in analogous conditions under the action of calixarene C107 both these activities decrease twice in comparison with control. Both under the in vitro and in vivo conditions, M3 fragment (the structural component of C107) does not change the values of investigated enzymatic activities. The biochemical mechanisms of calixarene C107 action on Na+, K(+)-ATPase activity in PM of rat hepatocytes are discussed.

[Effect of pH on ATPase myosin activity of different muscle types]. / Vplyv pH seredovyshcha na ATFaznu aktyvnist' miozynu riznikh typiv m'iaziv.

The influence of pH in the medium on ATPase myosin activity in different muscle types was investigated. It has been found that myosin ATPase had two maxima with different values of the specific activity in cardiac, skeletal and smooth muscles depending on pH, namely: 6.0-6.5 and 9.0-9.5. The dependence of physiological properties of different muscle types on the physical-chemical and structural peculiarities of myosin has being discussed.

[Transfer factor modulates inhibitory action of neurotransmitters on intestinal smooth muscles]. / Faktor perenosu moduliuie hal'mivnu diiu neiromediatoriv na hladen'ki m'iazy kyshechnyka.

It has been shown that Transfer factor (TF) to Staphilococcus aureus antigens blocked ATP-induced component of the inhibitory junction potential in taenia coli smooth muscle from guinea-pig, and converted an inhibitory action of exogenous ATP into an exciting one (instead of the hyperpolarization of the smooth muscle, TF induced its depolarization). TF at 10-6 mg/ml converted the relaxing effects of sodium nitroprusside (nitric oxide donor) into exciting ones in smooth muscle strips. Higher concentrations (10-5-10-3 mg/ml) of TF slightly amplified the relaxing effect of sodium nitroprusside. Both a- and b-adrenergic activation in taenia coli smooth muscle were not sensitive to that agent.

[Mathematical model of trans-sarcomere exchange of calcium ions and Ca2+-dependent control of smooth muscle contractile activity]. / Matematychna model' transsarkolemnoho obminu ioniv kal'tsiiu ta Ca2+-zalezhnoho kontroliu skorotlivoï aktyvnosti hladen'koho m'iaza.

The mathematical model of smooth muscles contractile activity Ca(2+)-dependent control has been proposed on the base of Ca ions trans-sarcomal exchange biochemical mechanisms interpretation in myocytes. While analysing the model the conclusion should be made that kinetic parameters changes (in relation to Ca ions) Mg2+, ATP-dependent calcium pump of plasma membrane--Michaelis constant Km and transport process maximal velocity Vmax-render the effect on the character of the intracellular calcium transients and profile of full mechanokinetic curve. As well one more conclusion has been made that plasma membrane Mg2+, ATP-dependent calcium pump, which kinetic parameters under the physiologic conditions are subjected to modulation as the result of metabolic, pharmacologic and physico-chemical factors fulfills the essential role in supplying Ca(2+)-dependent control of the smooth muscles contractile response full cycle.

[Effect of staphylococcus active substances on ATPase activity of smooth muscle actomyosin and myosin]. / Vpliv aktyvnykh substantsii stafilokoka na ATP-aznu aktyvnist' aktomiozynu ta miozynu hladen'kykh m'iaziv.

The effect of staphylococcus active substances--protein A (PA) and peptidoglican (PG) at concentrations 10(-6)-10(-2) mg/ml on the ATPase activity of pig stomach natural actomyosin and myosin was studied. It was shown that PA and PG at direct contact with smooth muscle contractile proteins caused the activation and inhibition of ATPase activity, respectively. On the basis of this investigation it was assumed that staphylococcal active substances were able to modify of the ATPase activity smooth muscle contractile proteins perhaps via direct action on the myosin molecule, which could be accompanied by conformational changes of the active center of myosin ATPase.

[Phenomenologic mechanokinetic model of Ca2+-dependent contraction-relaxation of smooth muscle]. / Fenomenolohichna mekhanokinetychna model' Ca2+-zalezhnoho skorochennia-rozslablennia hladen'koho m'iaza.

Phenomenological mechanokinetic model of the smooth muscle contraction response that based on the idea of separate contraction and relaxation phases additivity realizing in the Ca(2+)-dependent "parallel" dynamic regime was elaborated and tested in the biophysical tensometrical experiment. This model application may be perspective for the further development of conceptions concerning kinetic and energetic regularities of muscle contraction and its quantitative characteristics.