Hypertension artérielle et résistances vasculaires

in Revue Médicale de Liège (1995), 50(9), 365-372

L'anomalie hémodynamique caractéristique de l'hypertension artérielle est l'augmentation des résistances vasculaires. Ces résistances siègent principalement au niveau de petites artères et d'artérioles ... [more ▼]

L'anomalie hémodynamique caractéristique de l'hypertension artérielle est l'augmentation des résistances vasculaires. Ces résistances siègent principalement au niveau de petites artères et d'artérioles précapillaires de diamètre inférieur à 300Il et sont le résultat de modifications essentiellement anatomiques. La média est de loin la couche la plus épaisse de la paroi de ces vaisseaux caractérisés,au stade d'hypertension chronique, par un rapport épaisseur de média sur lumière accru. Contrairement à l'animal hypertendu, cette modification est, chez l'homme, liée à un remodelage vasculaire (réarrangement cellulaire sans vraie hypertrophie ou hyperplasie), en relation avec une anomalie endothéliale (réduction de production de monoxyde d'azote, augmentation de production d'endothéline-l). L'intérêt pour ces modifications structurelles réside dans l'espoir d'influencer favorablement ces lésions notamment par des traitements spécifiques. Récemment, une étude canadienne a rapporté qu'un inhibiteur de l'enzyme de conversion, à même efficacité antihypertensive qu'un bêtabloquant, était seul capable de normaliser les anomalies structurelles de la média et de corriger (partiellement) la dysfonction endothéliale caractérisant également l'hypertendu après 27ms de traitement (étude chez l'homme, à partir de biopsies répétées de tissu sous-cutané, selon la technique proposée par les groupes de Heagerty et Mulvany). Cette observation jointe aux données expérimentales et à quelques données humaines suggère que les inhibiteurs de l'enzyme de conversion posséderaient bien des propriétés indépendantes de leur effet antihypertenseur permettant une correction des anomalies vasculaires dans l'hypertension. Ces travaux méritent cependant une confirmation sur un grand nombre de patients. Ils ont l'intérêt d'ajouter une note explicative pathogénique aux bénéfices déjà observés en épidémiologie dans la décompensation cardiaque, l'infarctus myocardique ou la protection rénale lors de l'utilisation de ces molécules. [less ▲]

Quantitative assessment of erythropoiesis in haemodialysis patients demonstrates gradual expansion of erythroblasts during constant treatment with recombinant human erythropoietin.

in British Journal of Haematology (1995), 89(1), 17-23

Recombinant human erythropoietin (rHuEpo) has been shown to be effective in correcting the anaemia of chronic renal failure. It has been reported that reticulocytes as well as erythroid progenitors ... [more ▼]

Recombinant human erythropoietin (rHuEpo) has been shown to be effective in correcting the anaemia of chronic renal failure. It has been reported that reticulocytes as well as erythroid progenitors increase within 1-2 weeks, with no further elevation beyond this time interval. However, the erythroblast pool is quantitatively the most important compartment of erythropoiesis, and the rate, extent and duration of the expansion of erythropoietic activity in response to rHuEpo is not known. Treatment with rHuEpo was given to 64 patients i.v. thrice weekly after haemodialysis. The effect of rHuEpo was obvious from the early elevation of reticulocyte counts, but much of this increase was due to a rapid output of shift reticulocytes which levelled off after a few weeks. Serum transferrin receptor (TfR), a quantitative measure of erythropoiesis, increased progressively over 6 weeks to reach a plateau phase at about twice baseline values. The Hct increased progressively and continued to rise steadily after the TfR plateau was reached. The speed and extent of the expansion of erythropoietic activity correlated with the later haematological response to rHuEpo. When rHuEpo was discontinued, erythropoietic activity returned progressively to baseline values, to rise again gradually when treatment was resumed. Part of the Hct increase was also due to haemoconcentration. The results indicate that changes in the various erythroid compartments vary considerably in intensity and speed, and that the erythroblast compartment in particular is slow to respond to modifications in the erythropoietin stimulus. [less ▲]

Le Monitoring de la pression artérielle en pratique médicale : apports et limites

in Blood Pressure Profil (1994), 3

"L'article de Mme Saint-Remy et de G. Rorive constitue une bonne mise au point sur les controverses qui continuent à se développer autour de la place à réserver au monitorage ambulatoire de la pression ... [more ▼]

"L'article de Mme Saint-Remy et de G. Rorive constitue une bonne mise au point sur les controverses qui continuent à se développer autour de la place à réserver au monitorage ambulatoire de la pression artérielle (MAPA) dans l'évaluation du patient hypertendu. La variabilité importante universellement admise de la pression artérielle rend le concept du monitorage pendant 24 heures particulièrement attrayant. L'utilité de cette nouvelle approche ne sera cependant définitivement établie que quand les résultats d'études prospectives visant à démontrer la supériorité du MAPA sur la mesure conventionnelle de la pression artérielle seront connus. Deux études sont au minimum actuellement en cours en ce sens : l'étude OVA et l'étude Systeur. En attendant, le manque de valeurs normatives est évidemment un handicap pour l'intérêt de la MAPA dans la pratique journalière et ce d'autant plus que le coût de cette nouvelle méthodologie reste élevé. Dans la revue de la littérature de ce numéro de Blood Pressure Profile, deux publications viennent confirmer ce qui est avancé dans l'article de Mme Saint-Remy. Bianchi et col, observant que la microalbuminurie est plus importante chez les hypertendus en l'absence de chute nocturne de la pression artérielle, argumentent en faveur du rôle de la MAPA dans l'évaluation du pronostic cardio-vasculaire du patient hypertendu. De plus, Mansoor et al, confirmant la meilleure reproductibilité de MAPA par rapport à la mesure conventionnelle de la pression artérielle, concluent également que la MAPA permettra de diminuer le nombre de patients à inclure dans des essais de pharmacologie clinique. Ces résultats, bien qu'encourageant pour les défenseurs du MAPA, ne doivent cependant pas nous faire oublier que la généralisation de l'utilisation de cette nouvelle technique est à l'heure actuelle prématurée" Prof. J.P. Degaute, Hypertension Clinic, Hôpital Universitaire Erasme, Chief Editor [less ▲]

Utility of non-invasive ambulatory bood pressure monitoring in a hypertension clinic

in CVD Epidemiology newsletter (1994), 49(Spring), 50

Interest in measuring endothelin (ET1) in cardiovascular pathology, hypertension and uremia

in Acta Clinica Belgica (1994), 49(6), 317

Plasma Na-K ATPase inhibitor activity and intracellular ions during hemodialysis

in International Journal of Artificial Organs (1993), 16(1), 23-30

We have investigated the relationship between plasma Na-K ATPase inhibitor activity (EDLS) and intracellular ions in 37 uremic hemodialysed hypertensive patients, and in 20 normotensive non uremic ... [more ▼]

We have investigated the relationship between plasma Na-K ATPase inhibitor activity (EDLS) and intracellular ions in 37 uremic hemodialysed hypertensive patients, and in 20 normotensive non uremic controls (NC). As compared with the NC population, significantly enhanced values for erythrocyte (RBC) Na, Ca, platelet cytosolic Ca and EDLS were observed in all the uremic patients tested just before a dialysis session, as well as a decrease in RBC Ca ATPase and in the platelet pH. In uremia, significant correlations have been noted between RBC Na and platelet Ca (r = 0.6) or systolic BP (r = 0.45); between platelet Ca and systolic blood pressure (r = 0.8) or diastolic BP (r = 0.5) and between EDLS and RBC Na, Ca or platelet Ca (r = 0.5). Anti-hypertensive treatment has no influence on these parameters. During dialysis, a significant decrease has been noted in RBC Na, Ca, platelet Ca, SBP (only in untreated patients) and EDLS and an increase in RBC Ca ATPase and platelet pH. These modifications are significantly correlated with the weight change. [less ▲]

Red Blood Cell Na-Li Countertransport, Hypertensive Heredity, and Cardiovascular Risk in Young Adults

in American Journal of Hypertension : Journal of the American Society of Hypertension (1993), 6(4), 314-316

The erythrocyte Na-Li countertransport (CT) has been considered as a marker of genetic propension to essential hypertension, but also to be linked to atherosclerosis risk factors. We have evaluated these ... [more ▼]

The erythrocyte Na-Li countertransport (CT) has been considered as a marker of genetic propension to essential hypertension, but also to be linked to atherosclerosis risk factors. We have evaluated these relationships by measuring the Na-Li CT, blood pressure levels, the family predisposition to hypertension, body mass index, subscapular skin-fold thickness, waist/hip ratio, and plasma lipids in 43 young adults (22 to 23 years; 13 with a positive family history of hypertension), followed since adolescence (+/- 10 years) to analyze the natural history of blood pressure in this period of life. The Na-Li CT was negatively correlated with the HDL cholesterol (r = -0.37) and the HDL cholesterol/total cholesterol ratio (r = -0.44). This transport system was positively correlated to family history of hypertension (r = 0.38), waist/hip ratio, and the diastolic blood pressure. When the family history of hypertension was present, Na-Li CT and diastolic blood pressure were higher (P < .05), but the HDL cholesterol was lower (P < .01). After separating people according to the blood pressure level during adolescence in two groups, one lower than the 75th percentile (P75), and one higher, we notice that the latter remains characterized by a higher systolic blood pressure. But neither the Na-Li CT nor family history of hypertension and plasma lipids could explain the difference in the blood pressure behavior during this period. Thus, an increase of RBC Na-Li CT activity in young adults would suggest a higher cardiovascular risk rather than to be a simple marker of a hypertensive risk. [less ▲]

Importance of Weight Loss and Sodium Restriction in the Treatment of Mild and Moderate Essential Hypertension

in Acta Clinica Belgica (1993), 48(4), 234-245

The effectiveness of non pharmacological treatment of chronic arterial hypertension has been evaluated in 116 treated or not primary hypertensive out-patients. Those receiving diuretics were however ... [more ▼]

The effectiveness of non pharmacological treatment of chronic arterial hypertension has been evaluated in 116 treated or not primary hypertensive out-patients. Those receiving diuretics were however excluded. This population was requested to follow for 3 months a modification of their usual diet characterized by salt restriction combined with energy intake restriction when the patients were above their ideal body weight. Only 62 patients (53%) completed the study. However, this approach was effective by decreasing blood pressure and total cholesterol. The weight loss appears the most effective way to decrease blood pressure in untreated patients, but needs 3 months to be significant. In drug-treated patients, the sodium restriction significantly influences the blood pressure level, already after 1 month. However, salt sensitivity has been noted, especially in the most severe forms of the hypertensive disease. The combination of both modifications (weight loss and sodium restriction) does not appear to be more effective than each separate dietary measure. [less ▲]

A sulfonylthiourea (BM 20) related to torasemide: a new loop diuretic with relative potassium-sparing properties

in Journal of Pharmacy & Pharmacology (1993), 45

A series of sulphonylthioureas related to torasemide, a high ceiling loop diuretic, were synthesized and found to inhibit the Na+ 2Cl- K+ co-transporter of the thick ascending limb of the loop of Henlé ... [more ▼]

A series of sulphonylthioureas related to torasemide, a high ceiling loop diuretic, were synthesized and found to inhibit the Na+ 2Cl- K+ co-transporter of the thick ascending limb of the loop of Henlé. Their diuretic properties were studied (30 mg kg-1) after oral administration to rats. Lipophilic derivatives very active in-vitro, were found inactive orally and intraperitoneally in rats. The four most active compounds were examined for their dose-dependent diuresis. Three of them showed a potency, water and electrolyte excretion similar to torasemide. The fourth molecule, a sulphonylthiourea (BM 20), exhibited relative potassium-sparing properties and a minimal diuretic dose of 0.001 mg kg-1, 200 times lower than torasemide. [less ▲]

Relation between sodium balance and cellular calcium in hypertension

in American Journal of Hypertension : Journal of the American Society of Hypertension (1993), 6