Na,K-ATPase and Ca-ATPase activities of the myocardial sarcolemma in aging rats after aorta coarctation: role of invertors.

In this work we used aorta coarctation as a model of myocardial hypertrophy. We studied the role of intracellular regulators of plasma membrane status-invertors-in the mechanisms of changes of membrane enzyme activities in the emergency stage of myocardial hypertrophy. We used Wistar rats of various ages: adult (6-8 months) and old (26-28 months) rats. It was shown that 4-6 days after aorta coarctation, in adult rats the activities of both Na,K-ATPase and Ca-ATPase of the sarcolemma of cardiomyocytes increased, but in old rats only the Ca-ATPase activity. Experiments with cell hybrids (cytosol of experimental rats and isolated sarcolemma of cardiomyocytes of intact rats) revealed that cytosol of cardiomyocytes of adult animals after aorta coarctation activated Na, K-ATPase and Ca-ATPase. Cytosol of old intact animals after aorta coarctation did not activate Na,K-ATPase, but activated Ca-ATPase. It was supposed that 4-6 days after aorta coarctation, intracellular regulators (invertors) activating Na,K-ATPase and Ca-ATPase of rat sarcolemma were synthesized in cytosol of adult animals. Invertors activating Na,K-ATPase did not appear after the aorta coarctation in old animals, but factors activating Ca2+-ATPase appeared. Cytosol of adult experimental rats activated Na,K-ATPase of sarcolemmas of cardiomyocytes of intact old animals. The data proved the ability of Na,K-ATPase of sarcolemma of old animals to respond to regulating factors. Based on the divergence between the results of experiments with the Na,K-ATPase and Ca-ATPase activities in old rats, it can be supposed that we were dealing with two different invertors.

[The hypothalamic mechanisms of the development of arterial hypertension in old age]. / Gipotalamicheskie mekhanizmy razvitiia arterial'noi gipertenzii v starosti.

The electrical activity of hypothalamic nuclei was found to change in accordance with changes in arterial blood pressure in old rabbits with reflexogenic hypertension. Stimulation of the hypothalamus induced an obvious increase in the blood pressure, considerable changes in cardiac activity, coronary insufficiency occurrence and alteration of the myocardium structure. An increase in excitability of the pressor structures of the anterior and posterior hypothalamic areas occurred with ageing. The age-induced changes in the hypothalamus could be either the primary mechanisms of development of hypertension, or they can be involved at later stages of the hypertension pathogenesis.

[Electrical activity and excitability of the thalamic nuclei of rabbits of various ages]. / Elektricheskaia aktivnost' i vozbudimost' iader talamusa u krolikov raznogo vozrasta.

In old-age rabbits, marked changes occur in the thalamic medial dorsal nucleus and lesser changes occur in electrical activity of the LGB. The photo-phonostimulation decreased the theta-rhythm frequency which had been increased. The latter suggests an impairment of the inhibitory processes in ageing as well as changes in the information flows to the brain cortex.

[Bioelectric activity of the hypothalamus of adult and old rabbits during prolonged vasopressin administration]. / Bioélektricheskaia aktivnost' gipotalamusa vzroslykh i starykh krolikov pri dlitel'nom vvedenii vazopressina.

In adult and old rabbits, the bioelectrical activity of supraotic, ventromedial and mamillary hypothalamic nuclei was studied after chronic (30 days) administration of vasopressin (0.2 U/kg of body weight). The hormone altered considerably the bioelectrical activity, these changes being uneven in various hypothalamic areas. Quantitative and qualitative differences of the changes were found in animals of different age. These changes of the hypothalamic bioelectrical activity seem to play an important role in the alterations of hemodynamic indices observed during chronic vasopressin administration.

Kallikrein-kinin system and adenosine metabolism system of blood and heart and their changes at hypothalamic-hypophyseal stimulation in rabbits of different age.

It was shown that kallikreinogen content was decreased in blood of old rabbits, kallikrein activity was somewhat increased, kininase activity was significantly decreased. In old animals, adenosine metabolism was activated, this being evident from the rise of 5'-nucleotidase and adenosine deaminase activity in blood and myocardium. Hypothalamic stimulation resulted in significant activation of the kallikrein-kinin system and sharp increase of kallikrein activity, the shifts being less marked in old animals than in adults. In adult animals, vasopressin administration elicited more marked activation of the kallikrein-kinin and adenosine metabolism systems.

[Changes in the kallikrein-kinin system of the blood following hypothalamo-hypophyseal stimulation of animals of different ages]. / Izmeneniia kallikrein-kininovoi sistemy krovi pri gipotalamo-gipofizarnoi stimuliatsii u zhivotnykh raznogo vozrasta.

Changes occurring in the formation and synthesis of kinins become irregular with ageing: the content of kallikreinogenes decreases, the activity of kininase and inhibitors of trypsin falls, and total blood activity of hydrolysis of ethyl--N--benzoil--L--arginine ether rises. Stimulation of the hypothalamus causes an obvious activation of the kalikrein--kinin system in adult animals: the contents of kallikreinogenes and kininogenes fall, the kallikrein activity sharply increases, whereas the kininase activity decreases. Both single and repeated administrations of vasopressin induce the same shifts of kallikrein--kinin system as the stimulation of hypothalamus. On repeated administrations of vasopressin the kininase activity rises.

[Role of protein biosynthesis activation in the mechanism of the negative chronotropic action of the vagus nerve and acetylcholine on the heart]. / Rol'aktivatsii biosinteza belka v mekhanizme otritsatel'nogo khronotropnogo deistviia bluzhdaiushchego nerva i atsetilkholina na serdtse.

In rats, the following data were obtained: a) acetylcholine activates the rate of protein biosynthesis in auricles in vitro; b) protein biosynthesis inhibitors (actinomycine D, sarcolysine, neutral rot, tolluidine blue) weaken the negative chronotropic effect of acetylcholine and vagus on the heart; c) anabolic hormones increase the cholinergic effect on heart; d) acetylcholine induces hyperpolarization of the myocardial fibers which is prevented by actinomycine D. The activation of protein biosynthesis followed by hyperpolarization of the pacemaker cells seems to play an important role in the mechanism of negative chronotropic effect of acetylcholine and vagus on the heart.

[Vasopressin concentration in the blood and sensitivity of the cardiovascular system to it during aging]. / Soderzhanie vazopressina v krovi i chuvstvitel'nost' k nemu serdechno-sosudistoi sistemy pri starenii

With aging the content of the blood vasopressin increases. In old animals smaller doses of vasopressin induce coronary insufficiency (rise of T wave, shift of S-T segment, disorders of the atrio-ventricular conductivity). On continuous administration of vasopressin (during a month), arterial hypertension appears only in old animals due to increase in cardiac output, stroke volume at unchanged cardiac rhythm, and to some decrease in the total peripheral resistance.

[Age-related peculiarities of the effect of angiotensin-2 on some hemodynamic indices]. / Vozrastnye osobennosti deistviia angiotenzina-2 na nekotorye gemodinamicheskie pokazateli

Changes occurring in some aspects of the hemodynamics following intravenous administration of different doses of angiotensin-2 were studied in tests staged on adult and old rabbits of both sexes. The older animals are shown to be more sensitive to this drug, for in them low doses (0.01, 0.1 gamma/kg) produced a significant elevation of the arterial pressure. On introduction of such doses the older animals more often demonstrate an accretion of the cardiac output. Introduction of the same doses to adult rabbits is more frequently attended by a rise of the total peripheral resistance. Upon administration of large doses of angiotensin-2 (1, 5 gamma/kg) the adult and older rabbits present more often a rise of the total peripheral resistance.