Determination of erythrocyte and platelet membranary permeability and its importance for the study of arterial pressure in physiological and pathological conditions.

The World Health Organization and the International Society of Hypertension continue to focus on assessing the cardiovascular risk of arterial hypertension and on developing a hierarchy of risk factors. Among the factors involved in the etiopathogeny of arterial hypertension, less attention has been given to the relations between the figurate elements of the blood (red cells and platelets) and the endothelial factors involved in vasomotricity. This motivates further research into the permeability of the erythrocyte and the platelet membrane in physiological and pathological conditions. Modern investigation methods have been employed in the study of a group of 100 patients with hypertension, both females and males, in various stages of the disease, who were compared with a group of controls. Results pointed to alterations of both eryhtrocyte and platelet membrane permeability dependent on the stage of the hypertensive disease and its complications. Despite the important individual variations that limit the diagnostic value of the investigations, they will contribute to an early diagnosis in the initial stages (I and II) of the disease and will point to the possibility of complications to occur. The correlations between alterations of platelet and erythrocyte permeability and the activity of gammaglutamyltransferase, the level of thiolic grouping and of cholesterol in the blood cell membrane provide additional information about the mechanism of interrelations between the latter and the vascular endothelial factors in physiological and pathological conditions such as arterial hypertension in various stages of evolution and its complications.

Activity of glutathione-s-transferase, gammaglutamiltransferase and catalase in the erythrocytic membrane in arterial hypertension.

Our clinical-biological study has been performed in patients with various clinical forms of arterial hypertension (AHT), as well as with sequelae-type complications from stroke that had occurred during the evolution of the disease. We performed biological determinations of the activity of four erythrocytic enzymes: glutathione-s-transferase (GST), catalase, gamma-glutamyltransferase (GGT), and lactate dehydrogenase (LDH). The results point to the existence of individual values and also of important differences depending on the presence of arterial hypertension complications. We found a moderate but significant increase of erythrocytic GGT in hypertensive patients compared to healthy controls. Erythrocytic GST and LDH were decreased in patients vs controls. The results of the enzymatic, erythrocyitc activities of GST, GGT, catalase and LDH can also be correlated with the parameters of erythrocyitc membrane permeability and with the thiolic groups, fibrinogen and ionic calcium concentration. The data described in this paper suggest the possible involvement of the disturbances mentioned above in the etiopathogeny of AHT.

Research on red cell membrane permeability in arterial hypertension.

Arterial hypertension, including the elucidation of hypertension pathogenic mechanisms involving elements in the composition of the blood, continues to represent a topical research area. Recent work, such as nuclear magnetic resonance studies looking into red cell permeability, illustrates the presence of modifications of red cell permeability to water (RCPW) related to the stage of arterial hypertension. The identification of a significant increase of RCPW compared to that present in the population with normal arterial pressure values can be useful both in early diagnosis and in warning about a possible predisposition for this condition. At the same time, the dynamic investigation of protonic relaxation time of both intra- and extra-erythrocytic water, the assessment of proton exchange time across the red cell and the calculation of permeability to water enable one not only to diagnose arterial hypertension but also to ascertain the evolution of the disease, its complications and the effectiveness of anti-hypertensive medication. Our studies have also proven the existence of a correlation between the values of systolic arterial pressure and red cell permeability to water. The curve describing the interdependence of the two values has the shape of a bell, in the case of males. The peak of the curve is reached for a systolic pressure of 160 mmHg and gets below the values of the control group in the case of systolic pressures above 200 mmHg. The RCPW test can also be considered a valuable indicator in evaluating the risk of stroke in hypertensive patients. In the chronic therapy of arterial hypertension with various types of anti-hypertensive drugs, one can note differences in the RCPW values related to the effectiveness of the respective medication, to the clinical form and stage of the disease, the sex of the patient as well as to the existence of cerebro-vascular complications.

Activity of Na+/K+-ATPase and of Ca++-ATPase under the action of adenosine triphosphate in experimental myocardial hypertrophy.

This paper presents the results of our research on the mechanisms involved in the modifications occurring in the activity of ionic pumps (Na+/K+-ATPase and Ca++-ATPase) at the level of the sarcolemma, the sarcoplasmic reticulum and mitochondrial membrane of the myocardial cell in experimental myocardial hypertrophy induced by isoproterenol. We also studied the effects of concomitant administration of adenosine triphosphate. Thus, we found the activity of the sarcolemmal Ca++-ATPase intensely increased under the action of isoproterenol, while Ca++-ATPase activity in the sarcoplasmic reticulum decreased significantly. At the same time, the Na+/K+-ATPase activity decreased both in the sarcolemma and in the sarcoplasmic reticulum. Administration of adenosine triphosphate induces opposite effects, of lower intensity, upon the activity of the two ATPase, that tend to offset the the effects of isoproterenol. This was found in the group of rats given concomitantly both isoproterenol and adenosine triphosphate. A better understanding of the processes involved in those modifications of membrane ATPase activity allows us to consider their different behaviour to isoproterenol and adenosine triphosphate as the expression of intrinsic mechanisms by means of which the myocardial cell intervenes in maintaining a physiological concentration of calcium ions (Ca++) that is necessary both in order to avoid a failure of the contractile apparatus and in order to preserve the mitochondria role of ATP supplier. Our results demonstrate the antiadrenergic action of adenosine triphosphate that attenuates isoproterenol effects on cardiac myocytes.