Indirect, noninvasive evaluation of pressure wave transmission in essential hypertension

Blood pressure, carotid-femoral and brachioradial pulse wave velocities were measured in 123 male subjects: 32 normal subjects and 91 age-matched patients with sustained essential hypertension. The ratio between brachioradial (BR) and carotid-femoral (CF) pulse wave velocities was used as a marker of pressure wave amplitude changes from the aorta to the brachial artery. The ratio was similar in normotensive and hypertensive subjects and decreased with age to the same extent in both populations. In older subjects, the decrease in the ratio indicated that the amplitude of pulse pressure was quite similar in the aorta and the brachial artery whether the subjects were normotensives or hypertensives. The study provided evidence that adaptive changes occur in the arterial (aortic) wall in hypertension, for the effects of age on pressure wave transmission are similar in normal subjects and hypertensive patients. Such findings may be of prime importance in understanding the brachial blood pressure readings of patients with hypertension.

Atrial natriuretic peptide decreases contractility of cultured chick ventricular cells

To determine whether atrial natriuretic peptide (ANP) has an inotropic effect, the contractility of spontaneously beating cultured chick embryo ventricular cells was studied in response to rat-ANP (1-23) superfused at concentrations ranging from 10(-10) M to 2.5 x 10(-7) M. r-ANP reversibly decreased contractility with a threshold concentration of 10(-8) M; at the highest concentration, r-ANP decreased contractility to a moderate extent (-30 +/- 4%) r-ANP increased dose-dependently intracellular cGMP levels. Stimulation of contractility with [Ca2+], the calcium-channel agonist BAY K 8644 or isoproterenol attenuated to various degrees the inhibitory effect of r-ANP. By contrast, the inhibitory effect of r-ANP on contractility was unchanged or even enhanced after stimulation of contractility by angiotensin II. There was no difference in r-ANP-induced increase in cGMP whether cells were pre-incubated with angiotensin II or not. These results indicate that r-ANP was able to decrease contractility of cultured cardiac myocytes and suggest a preferential antagonism of the inotropic effect of angiotensin II.

Endogenous opiate system and dihydropyridine-induced central regulation of sympathetic tone in rats

Intracerebroventricular injections of nicardipine (10 micrograms/kg) to SHR induced hypotension which was suppressed by pretreatment with 6-OHDA. This hypotension was also inhibited by a previous injection of naloxone (100 micrograms/kg i.c.v.) whereas the hypotension induced by intravenously injected nicardipine (10 micrograms/kg) was not changed. It is suggested that the release of endogenous opioids is involved in the sympatho-inhibitory effect of centrally administered dihydropyridine calcium channel antagonists.

Non-invasive ultrasonic study of maximal aortic blood acceleration in patients with borderline and sustained essential hypertension

Using a pulsed Doppler method to evaluate the aortic velocity curve transcutaneously, the maximal aortic blood acceleration was evaluated in normal subjects and in age-matched patients with borderline and sustained essential hypertension. Maximal aortic blood acceleration was significantly elevated in patients with borderline hypertension and remained within the normal range in patients with sustained hypertension. Since maximal aortic blood acceleration is relatively insensitive to preload and afterload, these findings might give indirect information on the contractile state of the myocardium in patients with hypertension.

Flow-dependent vasodilation of the brachial artery in essential hypertension: preliminary report

Brachial artery haemodynamics including brachial artery diameter and local blood flow velocity were studied in 10 normotensive subjects and 10 age-matched hypertensive patients. A bidimensional pulsed Doppler system was used at rest, during a 2-min period of distal circulatory occlusion and during reactive hyperaemia. The kinetics of changes in blood flow velocity and brachial artery diameter were determined during successive and reproducible manoeuvres. The two parameters decreased significantly during distal artery occlusion in both groups. During reactive hyperaemia, blood velocity reached similar maximal values in both groups and brachial artery diameter increased significantly in both normotensives and hypertensives. Changes in the brachial artery diameter during reactive hyperaemia were positively and significantly correlated to changes in blood flow velocity recorded at the same level. No significant difference was found between normotensives and hypertensives. This study has provided a demonstration of velocity-dependent variations in the diameter of a large artery in humans; the results suggest that velocity-dependent vasodilation of the brachial artery is not impaired in essential hypertension.

Atrial natriuretic peptide decreases contractility of cultured heart cell: preliminary report

We tested the hypothesis that atrial natriuretic peptide (ANP) has a direct negative inotropic effect on the cultured chick embryo ventricular cell, an experimental system devoid of endogenous neurotransmitters. At 10(-8) and 2.5 x 10(-7) mol/l ANP [rat ANP-(1-23)] significantly and reversibly decreased contractility in spontaneously beating cells. The positive inotropic effect of angiotensin II (2.5 X 10(-7) mol/l) on spontaneously beating cells was fully antagonized by ANP (2.5 X 10(-7) mol/l) and the amplitude of contraction decreased below control levels. In contrast (1) the increase in contractility in response to extracellular calcium was significantly less altered by ANP and (2) the time-course of the positive inotropic effect of the calcium-channel agonist Bay-K-8644 (5 x 10(9) mol/l) or of the beta-adrenergic agonist isoproterenol (10(-6) mol/l) was unchanged by ANP. These results indicate that ANP-(1-23) has a direct negative inotropic effect on cultured chick heart cells and may affect intracellular messengers involved in the cardiac effects of angiotensin II.

The common carotid circulation in patients with essential hypertension

We review carotid artery hemodynamics in hypertensive men, with particular reference to common carotid artery diameter and blood flow, and emphasize the changes in artery diameter and compliance implied by antihypertensive therapy.

Reversion of cardiac hypertrophy and reduced arterial compliance after converting enzyme inhibition in essential hypertension

Blood pressure, forearm arterial hemodynamics (with a pulsed Doppler flowmeter), and echocardiographic parameters were studied in 16 patients with sustained essential hypertension before and 3 months after administration of the converting enzyme inhibitor perindopril. In a single-blind study versus placebo, it was shown that perindopril significantly reduced blood pressure (p less than 0.01), whereas there was an increase in brachial blood flow (p less than 0.01) because of a simultaneous increase in blood flow velocity (p less than 0.01) and arterial diameter (p less than 0.01). During a 5-minute period of wrist occlusion, blood flow velocity was reduced to a greater extent with perindopril than with placebo (p less than 0.001), whereas corresponding reductions in arterial diameter were equivalent, indicating that the increase in diameter after perindopril could not be explained simply on the basis of flow-dependent dilatation. During active treatment, brachial artery compliance increased (p less than 0.01) and pulse wave velocity decreased (p less than 0.01), whereas there was no change in the tangential tension of the arterial wall, defined as the product of mean arterial pressure and arterial diameter. Four weeks after treatment was stopped, blood pressure and forearm arterial hemodynamics returned toward baseline values. Cardiac mass was significantly decreased after perindopril (p less than 0.01) and remained decreased 4 weeks after cessation of treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Relative negative inotropic potencies of nine calcium channel blockers in cultured heart cells

The direct inhibitory effects on contractility and beating rate of the calcium channel blockers diltiazem, verapamil and dihydropyridine derivatives nicardipine, nifedipine, nitrendipine, PY 108-068, (+/- ) PN 200-110 and its 2 stereoisomers, were compared in cultured chick embryo ventricular cells. In spontaneously beating cells, the negative inotropic and chronotropic potencies of nicardipine, nifedipine, nitrendipine and PY 108-068 were not significantly different. The inhibitory effects of verapamil, nifedipine and nicardipine were studied in cells electrically driven at a frequency close to their spontaneous beating rate: verapamil, nifedipine and nicardipine had similar negative chronotropic potencies; when the rate of stimulation was increased 1.5 and 2-fold, a frequency-dependent inhibitory effect on contraction was shown for verapamil, but not for nifedipine and nicardipine. Therefore, in our model, where the effects of beating rate on the amplitude of contraction were taken into account, no significant difference in the direct negative inotropic potenties of nifedipine and nicardipine was shown.

Central modulation of baroreceptor reflex response to phenylephrine by dihydropyridines in rats

The effects of two dihydropyridine derivatives, the calcium channel agonist BAY k 8644 or the antagonist PN 200-110, on the central nervous components of the baroreceptor reflex control of heart rate during activation of baroreceptors by phenylephrine (2 micrograms i.v.) were studied in pentobarbital-anesthetized normotensive (Wistar) rats and spontaneously hypertensive rats (SHR). To rule out an effect on peripheral vessels or on the sinoauricular node (or on both), BAY k 8644 and PN 200-110 were administered intracerebroventricularly (i.c.v.) at doses that did not change blood pressure. Baroreceptor reflex sensitivity was calculated as the slope of the relationship between systolic arterial pressure and heart period. Baroreceptor reflex sensitivity increased with time following the onset of anesthesia. In SHR, injection of BAY k 8644 (3 micrograms/kg i.c.v.) suppressed the time-dependent increase in baroreceptor reflex sensitivity. The inhibitory effect of BAY k 8644 (3 micrograms/kg i.c.v.) on the time-dependent increase in baroreceptor reflex sensitivity was suppressed by pretreatment with PN 200-110 (0.6 microgram/kg i.c.v.) but not with the solvent, indicating that the central effect of BAY k 8644 occurred at the level of specific dihydropyridine binding sites. In addition, the inhibitory effect of BAY k 8644 (3 micrograms/kg i.c.v.) on the time-dependent increase in baroreceptor reflex sensitivity was suppressed by pretreatment with the muscarinic antagonist atropine methylnitrate (80 micrograms/kg i.c.v.) but not with the solvent. In normotensive rats, the time-dependent increase in baroreceptor reflex sensitivity was not significantly altered by BAY k 8644 (3 micrograms/kg i.c.v.).(ABSTRACT TRUNCATED AT 250 WORDS)

Increased response of brachial artery diameter to norepinephrine in hypertensive patients

The hyperresponsiveness of small arteries to norepinephrine is well documented in essential hypertensive patients. Our objective was to investigate in situ the reactivity to norepinephrine of the diameter of large arteries, which are involved in the arterial disease of hypertension as well as small arteries. Brachial artery diameter, blood flow velocity, local volumic blood flow, and local vascular resistances were determined noninvasively with a pulsed Doppler system in 19 patients with essential hypertension and 9 normotensive subjects, before and after the administration of placebo (glucose) or increasing doses of norepinephrine (10, 20, and 40 ng.kg-1.min-1 iv) given in a single-blind fashion. In hypertensive patients, norepinephrine (40 ng.kg-1.min-1) induced 1) a significant decrease in brachial artery diameter, local blood velocity, volumic flow, and conductance and 2) a small increase in mean arterial pressure. These hemodynamic changes did not occur in the placebo group and were significantly greater in hypertensive patients than in normotensive subjects, although plasma norepinephrine increased to the same extent in both groups. We conclude that in hypertensive patients the increase in vascular reactivity to norepinephrine involves not only the resistive vessels but also the large arteries thus decreasing their conducting and buffering function.

Renal and systemic hemodynamics in borderline hypertension

Cardiac output (CO), renal blood flow (RBF), and glomerular filtration rate were measured in 29 young patients with borderline hypertension, in comparison with 26 normotensive controls of the same age and sex. In patients with borderline hypertension, both CO and RBF were significantly increased, whereas the RBF/CO ratio remained within the normal range. No significant changes in glomerular filtration rate and renal filtration fraction were observed. The study clearly demonstrated that renal ischemia was absent in young patients with borderline hypertension.

[Flow-dependent vasodilation of the brachial artery in the normotensive and essential hypertensive patient]

Brachial artery hemodynamics including brachial artery diameter (D), local blood flow velocity (V) and local volumic blood flow, was studied in 10 normotensive subjects (NT) and 10 age-matched hypertensive patients (HT) (50 +/- 4 vs 43 +/- 4 years; m +/- SEM; NS), using a bidimensional pulsed doppler system at rest (control period), during a 2 (or 4) mn-period of distal circulatory occlusion (DO) and during the following reactive hyperemia (RH). Kinetics of change in blood flow velocity and diameter were determined during successive and reproducible manoeuvres. V and D decreased significantly during DO. During RH (1) V reached similar maximum values in both groups (after 2 mn DO: NT: from 2.4 +/- 1.1 to 19.0 +/- 6.9 cm/s; HT: from 2.9 +/- 0.8 to 17.2 +/- 7.6 cm/s) and (2) D increased significantly in both groups (after 2 mn DO: NT: from 0.395 +/- 0.016 to 0.450 +/- 0.025 cm; p less than 0.001; HT: from 0.408 +/- 0.018 to 0.467 +/- 0.018 cm; p less than 0.001), reaching levels significantly higher than during the control period. The brachial artery vasodilation observed in both groups (NT: +12 +/- 3 p. 100; HT: +15 +/- 3 p. 100 of initial diameter) was significantly greater (p less than 0.001), than the reproducibility of the diameter measurement (3 +/- 1 p. 100). Mean arterial pressure and heart rate dit not change during the whole investigation. Increasing the duration of DO from 2 to 4 mn further enhanced the reactive blood flow velocity but did not change the magnitude of the reactive brachial artery vasodilation.(ABSTRACT TRUNCATED AT 250 WORDS)

[Central control of the baroreflex response to phenylephrine by dihydropyridines in the anesthetized rat]

We have previously shown that a calcium channel activator (BAY K 8644) and a calcium channel inhibitor (CCI) (nifedipine), both dihydropyridine derivatives (DHP), can modulate in opposite fashion calcium dependent mechanisms involved in the central control of blood pressure and heart rate in SHR but not in Wistar rats. These results suggested that central DHP receptor sites might modulate baroreflex function. Therefore, we studied in pentobarbital anaesthetized SHR, the effects of BAY K 8644 and PN (200-110) (CCI) on central integration of baroreflex function (ramp method: phenylephrine 2 microgram i.v.). In order to rule out peripheral vascular effects, BAY and PN were administered intracerebroventricularly (i.c.v.) at doses which did not change BP. Baroreflex sensitivity (BRS) increased with time following the onset of anesthesia. In SHR, i.c.v. injection of BAY (3 microgram/kg) but not PN (0.6 micrograms/kg) suppressed the time dependent increase in BRS. The inhibitory effect of BAY on the time-dependent increase in BRS was suppressed by a pretreatment with PN (0.6 micrograms/kg i.c.v.) and by a pretreatment with the muscarinic antagonist atropine methylnitrate (80 micrograms/kg i.c.v.). BAY i.c.v. dit not change BRS in Wistar rats. These results indicate that DHP may centrally modulate BRS in SHR and suggest a central sympatho-excitatory effect for BAY mediated by an enhanced release of acetylcholine.

[Atrial natriuretic factor diminishes the contractility of the cardiac cell in culture]

The hypotensive effect of ANP has been associated with lowered cardiac output. Although only minor or no negative inotropic effect was found in vitro, a direct myocardial depressant effect of ANP remains a possible mechanism in vitro, in addition to the reduction in cardiac preload. Therefore we tested the hypothesis of a direct negative inotropic effect of ANP on the cultured chick embryo ventricular cell, an experimental system which contains no neural elements and no endogenous neurotransmitters. ANP (rat-ANP 1-23) 10(-8) M significantly and reversibly decreased contractility in spontaneously beating cells. A further decrease (-30 +/- 4 p. 100 of initial amplitude of contraction) was observed at 2.5 x 10(-7) M: -17 +/- 4 p. 100 of initial amplitude). The positive inotropic effect of angiotensin II (2.5 x 10(-7) M) on spontaneously beating cells was fully antagonized by ANP (2.5 x 10(-7) M) and amplitude of contraction decreased under control levels. By contrast (1) the increase in contractility in response to extra-cellular calcium (increased from 1.5 to 2.1 mM) was significantly less altered by ANP and (2) the time-course of the positive inotropic effect of the calcium-channel agonist BAY K 8644 (5 x 10(-9) M) or the beta-adrenergic agonist isoproterenol (10(-6) M) was unchanged by ANP. These results indicate a direct negative inotropic effect of ANP (1-23) on cultured chick heart cells and suggest an effect on intracellular messengers involved in the cardiac effects of angiotensin II.(ABSTRACT TRUNCATED AT 250 WORDS)

[Pulse wave velocity and ambulatory blood pressure in essential arterial hypertension]

Cardiovascular morbidity and mortality of hypertensive patients is mainly related to lesions of large arteries. Arterial distensibility estimated by carotid-femoral pulse wave velocity (PWV) was evaluated in 22 patients with sustained essential hypertension, together with three different methods of blood pressure (BP) measurement: mercury sphygmomanometer, semi-automatic BP recording using the Dinamap apparatus and 24 H ambulatory BP monitoring using the Spacelabs Monitor (5200). Table shows that, while PWV was not correlated with BP measured by mercury sphygmomanometer, it was strongly and positively correlated with BP measured by the other procedures. The best correlation coefficient was noted for the systolic BP measured in the Day Time (7 h-22 h) by the ambulatory method. This study shows that BP Monitoring correlates more strongly than clinic or casual BP with indices of target organ damage. (Table: see text).

[Pulse pressure and echocardiographic parameters in essential arterial hypertension]

We measured systolic, diastolic, mean (MAP) and pulsed (PP) arterial pressures (Dinamap 845 XT), carotid femoral pulse wave velocity (PWV) and cardiac parameters (echocardiography) to evaluate myocardiac mass and indexed cardiac mass to body surface area (IM) in 47 subjects (11 normotensives and 36 with sustained essential hypertension). Hypertensives were allocated between two groups with same age, weight and height, same mean arterial pressure (119.8 +/- 9.1 mmHg, 119.7 +/- 11.9 mmHg, NS) and PWV (11.90 +/- 2.20 m/s, 12.51 +/- 1.83 m/s, NS): group I (22 subjects) with pulsed pressure less than 60 mmHg, group II (14 subjects) with pulsed pressure greater than or equal to 60 mmHg. (Table: see text). Newman-Keuls between group I and group II: p less than 0.01 for cardiac mass and IM, p less than 0.001 for PP. Cardiac mass (p less than 0.01) and indexed mass to body surface area (p less than 0.01) were greater in group II (with pp greater than or equal to 60 mmHg) than in group I.

CONCLUSION

arterial hypertension is linked with left ventricular hypertrophy which is increased when pulsed pressure is enhanced. This fact could give evidence of importance of pulsatory work in cardiac consequence of hypertension.

[Effects of beta-blockers on hemodynamics of the forearm after tobacco stimulation]

In mild hypertension, a betablocker treatment could reduce cardiovascular events. But in smoking men the benefit disappears and this interaction is unexplained. In 6 healthy non smoking men, we studied the effects of acute oral administration of propranolol (80 mg) pindolol (15 mg) and placebo after cigarette smoking (CS) (two cigarettes within 10 minutes). In a double blind cross over randomized study, arterial pressure and heart rate (HR) were recorded within 20 minutes after CS. Brachial artery diameter (D), Local vascular Resistance (RL), Local arterial Compliance (CL) and pulse wave velocity (VOP) were determined non invasively (using a pulsed doppler system) before and 20 mn after CS. Under placebo, mean arterial pressure (PAM), HR and RL increased significantly after CS (+9.2 +/- 3 mmHg, +4.5 +/- 3 b/mn and +36 +/- 14 per cent, respectively). These modifications were not different after propranolol, pindolol or placebo (ANOVA). Arterial distensibility (CL) was decreased after CS and this alteration was not prevented by beta-blockers. Brachial artery diameter was not modified after CS. Our results demonstrate that acute treatment with non selective beta-blockers with or without sympathomimetic intrinsic activity does not prevent haemodynamic modifications induced by cigarette smoking.

Central and peripheral cardiovascular effects of the enantiomers of the calcium antagonist PN 200-110

The negative inotropic effects and the central and peripheral hypotensive effects of (+) and (-) PN 200-110 were investigated in cultured chick heart cells and in spontaneously hypertensive rats, respectively. There was a large difference in negative inotropic potency between the two enantiomers in cultured chick embryo ventricular cells: the (+) enantiomer was 140 fold more potent (IC50 = 1.1 +/- 0.2 nM) than the (-) enantiomer (IC50 = 160 +/- 20 nM). (+) PN 200-110 was 10 fold more potent than (-) PN 200-110 in lowering blood pressure after intravenous injection and only three fold more potent after intra-cerebroventricular injection (i.c.v.) into pentobarbital-anaesthetized spontaneously hypertensive rats. I.c.v. administered (+) PN 200-110 (1 microgram/kg) partially antagonized the hypertensive response to i.c.v. administered BAY K 8644 (30 micrograms/kg), a calcium channel agonist, while the same dose of the (-) enantiomer did not change the i.c.v. BAY-induced increase in blood pressure. These results suggest that the dihydropyridine calcium channel antagonist, PN 200-110, may act centrally and stereoselectively at the level of the dihydropyridine receptor sites involved in the control of blood pressure in spontaneously hypertensive rats.

Converting enzyme inhibition and the common carotid circulation in older patients with sustained essential hypertension

Arterial diameter, blood flow and vascular resistance of the common carotid artery were studied using a pulsed Doppler system in patients with uncomplicated sustained essential hypertension and compared with age-matched normal subjects. In hypertensive patients below the age of 45 years, arterial diameter and blood flow remained within the normal range, while vascular resistance was increased. In hypertensive patients over 45 years of age, arterial diameter was also normal, but blood flow was reduced and vascular resistance markedly increased. Thus, both small and large arteries were altered in the common carotid circulation of patients with sustained essential hypertension. Acute oral administration of converting enzyme inhibitor produced dilatation of both small (vascular resistance) and large (arterial diameter) arteries in the carotid circulation. In addition, in older patients, blood flow significantly increased and vascular resistance markedly decreased both in acute and long-term situations. Thus converting enzyme inhibition was able to reverse the abnormalities of the common carotid circulation of older subjects with sustained essential hypertension.

Hemodynamics of the carotid artery after vasodilation in essential hypertension

We performed simultaneous noninvasive measurements of common carotid artery and brachial artery hemodynamics in nine normal subjects and 10 subjects with sustained essential hypertension. In hypertensive subjects, brachial artery blood flow and forearm vascular resistance were in the normal range while carotid artery blood flow and carotid artery resistance were decreased and increased, respectively. The most important findings were the changes in the internal caliber of large arteries. Although the brachial and carotid artery diameters of hypertensive subjects were measured for the same level of mean arterial pressure, brachial artery diameter was significantly increased and carotid artery diameter was strictly normal as compared with values found in normal subjects. To assess whether carotid artery circulation could influence the baroreceptor reflex response to arteriolar vasodilation, carotid artery and brachial artery hemodynamics were measured in immediate succession in normotensive and hypertensive subjects before and after oral administration of cadralazine, a dihydralazine derivative. After cadralazine treatment, carotid artery tangential tension decreased in hypertensive subjects, and the changes were significantly correlated to the increase in heart rate. A similar correlation was found in normal subjects, but it was reset toward higher heart rates. These results indicate that the carotid artery does not behave like the brachial artery in response to a chronic increase in blood pressure. This behavior indicates intrinsic alterations of the arterial wall and might be involved in the resetting of the carotid baroreceptor reflex. Carotid artery circulation could play a role in hypertension by modulating the carotid baroreceptor mechanisms involved in the response to drug-induced arteriolar vasodilation.(ABSTRACT TRUNCATED AT 250 WORDS)

Sodium and large arteries in hypertension. Effects of indapamide

Epidemiologic studies evaluating arterial pulse wave velocity together with blood pressure indicate that: (1) salt intake has an independent effect on arteriolar tone and arterial wall properties, with the former indirectly and the latter directly contributing to increased arterial stiffness with age; and (2) normotensive adult subjects who follow a low sodium diet have reduced arterial stiffness and this effect is independent of blood pressure. Conversely, in elderly persons with isolated systolic hypertension, isotonic saline infusion causes a predominant increase in systolic pressure due to an increase in the stiffness of the arterial wall. The diuretic indapamide produces a decrease in blood pressure without significant change in brachial artery diameter. The result indicates a shift of the pressure-diameter curve, reflecting for the first time in humans a pharmacologic effect of the drug on arterial vessel. Furthermore, diuretic drugs may increase arterial distensibility and compliance in hypertensive patients, but this effect seems to be more pronounced in older than in younger subjects. In the latter, either activation of the sympathetic nervous system or potassium depletion, or both, might counteract the improvement in arterial distensibility caused by blood pressure reduction and sodium depletion. Based on epidemiologic, clinical, and pharmacologic studies, this critical review suggests that, in patients with essential hypertension, changes of sodium intake in diet or administration of diuretics, or both, affect the status of large arteries independently of blood pressure changes.

Central and peripheral hypotensive effects of the optical isomers of nicardipine, a dihydropyridine calcium channel antagonist, in rats

Central and peripheral hypotensive effects of (+)- and (-)-nicardipine (1-10 micrograms/kg i.v. or i.c.v.) were investigated in normotensive and SH rats. The results suggest that a stereoselectivity exists for the peripheral and central hypotensive effects of the nicardipine isomers. (+)-Nicardipine was shown to be 3-8 times as potent as the (-) isomer in reducing blood pressure in all the experiments.

Central interactions between dihydropyridines and cholinergic systems in the control of blood pressure in rat

Intracerebroventricular (i.c.v.) injection of the 1,4-dihydropyridine (DHP) calcium channel agonist, Bay K8644 (30 micrograms/kg) increased mean blood pressure and the K+-evoked release of [3H]acetylcholine ([3H]ACh) from hippocampal slices in spontaneously hypertensive rats (SHR). The Bay K8644-induced hypertension was inhibited by a pretreatment with methylatropine (80 micrograms/kg i.c.v.). In SHR, nicardipine, a DHP calcium channel antagonist, reduced mean blood pressure when i.c.v. injected (10 micrograms/kg). The nicardipine-induced hypotension was reduced by a pretreatment with hemicholinium-3 (20 micrograms, i.c.v.). Nicardipine (1 microM) did not modify, in SHR, the K+-evoked release of [3H]ACh, but inhibited the Bay K8644-induced increase in the ACh release. In normotensive rats, neither Bay K8644 nor nicardipine modify blood pressure, when centrally injected, or the stimulated release of [3H]ACh from hippocampal slices. The participation of central DHP sites in the cholinergic transmission in genetic hypertension is discussed.

[Current treatment regimen in essential arterial hypertension]

The introduction in the treatment of arterial hypertension of angiotensin-converting enzyme inhibitors and calcium inhibitors, as well as the results of extensive multicentric therapeutic trials, suggest that the prescription of antihypertensive drugs will be profoundly altered in the forthcoming years. The "step by step" approach will be abandoned, and each patient will receive one or two drugs chosen for being the most selective and most suitable for his case. These more personalized long-term treatments will be better tolerated, and the greater patient's compliance will make them more effective drugs to the underlying pathology (smoking habits, blood lipid disorders, early arterial lesions) the antihypertensive treatment will have a greater reducing effect on cardiovascular morbidity and mortality.

[Index of arterial and venous compliance and echocardiographic parameters in essential permanent arterial hypertension]

Forearm venous tone (FVT), carotido-femoral pulse wave velocity (PWV), and left ventricular end diastolic diameter (LVD), left ventricular posterior wall thickness (LVPWT), myocardiac mass (MM), measured by echography were evaluated on 25 subjects with sustained essential hypertension and 30 normotensive subjects with same age and same sex. For the overall population, FVT is positively correlated with LVD (r = 0.45, p less than 0.001), with LVPWT (r = 0.37, p less than 0.01) and with MM (r = 0.55, p less than 0.001). PWV is not correlated with LVD but is positively correlated with LVPWT (r = 0.48, p less than 0.001) and with MM (r = 0.40, p less than 0.01). Stroke volume is positively correlated with FVT (r = 0.42, p less than 0.01), but not with PWV. This study shows that in a population of normals and sustained essential hypertensive subjects: i) indexes of venous compliance are correlated with myocardial thickness, myocardiac mass, left ventricular diameter and stroke volume, while ii) indexes of arterial compliance are only correlated with myocardial thickness. Thus, the modifications of arterial and venous compliance observed in sustained essential hypertension influence cardiac structure and function.

Brachial artery cross-sectional area and distensibility before and after arteriolar vasodilatation in men with sustained essential hypertension

Blood pressure, volume distensibility (VD), and cross-sectional area (CSA) of the brachial artery were studied using pulsed Doppler systems in 51 patients with sustained essential hypertension in comparison with 21 normotensive controls of the same age. In hypertensive patients, in baseline conditions, CSA was significantly increased and VD decreased--the two parameters strongly and negatively correlated independent of the blood pressure level. Arteriolar vasodilatation was produced by three pharmacological agents--cadralazine, a dihydralazine-like compound; nicorandil, a nicotinamide derivative; and nitrendipine, a calcium entry blocker. For the same blood pressure reduction, cadralazine significantly reduced CSA, while nicorandil and nitrendipine increased it. Nitrendipine significantly increased VD, which was not modified by cadralazine and nicorandil. For cadralazine and nicorandil, a significant negative correlation was observed between VD and CSA. The relationship was the same as in baseline conditions. With nitrendipine, no significant correlation was observed between the two parameters. At any given CSA, distensibility was higher with nitrendipine than with cadralazine or nicorandil. The study provided evidence that, in men with essential hypertension, in basal conditions, the negative relationship between VD and CSA reflected intrinsic alterations of the arterial wall, while cadralazine, nicorandil, and nitrendipine caused a similar degree of arteriolar dilatation, nicorandil and nitrendipine caused active arterial dilatation as well, and changes in distensibility after drug administration were not directly related to blood pressure level and were mediated either by predominant geometrical modifications (cadralazine, nicorandil) or by the predominant relaxing effect of the drug on arterial smooth muscle tone (nitrendipine), or both.

Systolic hypertension in patients with arteriosclerosis obliterans of the lower limbs

Intraarterial blood pressure, brachial artery compliance and diameter, and pulse wave velocity were determined in 20 patients with arteriosclerosis obliterans of the lower limbs (AOD) in comparison with 10 age- and sex-matched controls. With the same mean arterial pressure as in controls, patients with AOD exhibited a significant increase in systolic pressure and decrease in diastolic pressure, resulting in an increase in pulse pressure. While brachial artery diameter and pulse wave velocity remained nearly within the normal range, arterial compliance was significantly reduced and was negatively correlated with the level of pulse pressure. The study provided evidence that: atherosclerotic modifications in patients with AOD are associated with an increase in pulse pressure, which predominates on the increase in mean arterial pressure, increased pulse pressure is related to decreased arterial compliance, which reflects intrinsic modifications of the viscoelastic properties of the arterial wall.

Opposite central cardiovascular effects of nifedipine and BAY k 8644 in anesthetized rats

The central cardiovascular effects of the calcium channel blocker nifedipine and the calcium channel activator BAY k 8644 were studied in anesthetized and ventilated normotensive Wistar-Kyoto (WKY) or spontaneously hypertensive rats (SHR). Both drugs were administered in a 1.5-microliter volume into the lateral ventricle of the brain (i.c.v.) or into the cisterna magna (i.c.). The injection of vehicle alone (i.c. or i.c.v.) did not significantly change mean arterial pressure (MAP) or heart rate. Nifedipine (5 and 50 micrograms/kg) and BAY k 8644 (5 and 50 micrograms/kg) induced opposite effects on MAP when centrally injected. Nifedipine decreased MAP and induced a bradycardia (i.c.v.) or no change in heart rate (i.c.), and BAY k 8644 increased MAP without any significant change in heart rate (i.c. or i.c.v.). These effects were more marked with the highest dose of either drug. These effects seemed to be of central origin, since they were suppressed by ganglionic blockade by hexamethonium (100 mg/kg i.v.), whereas after hexamethonium the hypotensive and the hypertensive responses to intravenously injected nifedipine and BAY k 8644, respectively, were preserved. Bilateral vagotomy suppressed the bradycardia induced by i.c.v. administered nifedipine. Previously i.c.v. administered nifedipine (5 micrograms/kg) antagonized the pressor response to BAY k 8644 (5 micrograms/kg i.c.v.). Changes in MAP and heart rate were significantly more marked in SHR than in WKY. These results indicate that a calcium channel inhibitor and a calcium channel activator can modulate in opposite fashion central mechanisms involved in blood pressure control.

Captopril + hydrochlorothiazide 24 h ambulatory monitoring effects

The purpose of this study was to evaluate over a 24 h period the antihypertensive effect of captopril 50 mg + hydrochlorothiazide (HCTZ) 25 mg once a day in mild to moderate hypertension. Ambulatory recordings over 24 h of the blood pressure using the Spacelabs system were performed, at the end of a 15-day placebo period and after giving captopril + HCTZ for 45 days. Captopril + HCTZ significantly decreased (P less than 0.001) systolic and diastolic blood pressures for both the diurnal period (8 h to 22 h) and the nocturnal period (22 h to 8 h). No change in heart rate was observed. For further analysis, the mean hour values of blood pressure and heart rate were calculated. A constant decrease of the systolic and diastolic blood pressure throughout the 24 h was obtained after captopril + HCTZ without any change in heart rate and in nyctohemeral variations. The study provided evidence that, in patients with mild to moderate essential hypertension, captopril + HCTZ once a day decreased systolic and diastolic blood pressure all day long without any change in the heart rate and the blood pressure nyctohemeral cycle.

Comparative effects of captopril and isosorbide dinitrate on the arterial wall of hypertensive human brachial arteries

Blood pressure, diameter, volume distensibility, and compliance of brachial artery were measured noninvasively in patients with sustained essential hypertension before and after Captopril in 11 patients and before and after isosorbide dinitrate (ISDN) in 11 other patients. Both drugs caused a similar significant decrease in mean arterial pressure (MAP) (p less than 0.001) and increase in arterial compliance (p less than 0.001), defined as the product of arterial volume by distensibility. ISDN increased arterial compliance through a dominant increase in arterial diameter (0.524 +/- 0.029 vs. 0.455 +/- 0.022 cm; p less than 0.001) and hence volume, whereas Captopril increased compliance through an increase in volume distensibility (0.20 +/- 0.02 vs. 0.12 +/- 0.02% change volume/mm Hg; p less than 0.001) with minimal changes in arterial diameter. The study provided evidence that of the two vasodilating drugs, ISDN and Captopril, only Captopril caused a predominant pharmacological relaxing effect on the wall of hypertensive human brachial arteries studied in situ.

[Non-invasive study of the role of carotid distension in the baroreflex response to the arteriolar vasodilator cadralazine in essential hypertension]

Using pulsed Doppler methods, hemodynamics of the common carotid and the brachial arteries were measured in 10 patients with essential hypertension. After vasodilatation due to Cadralazine, a Dihydralazine-like substance, mean arterial pressure significantly decreased and heart rate increased. Change in PRA was significantly and positively correlated with the change in heart rate. In the brachial artery circulation, diameter and vascular resistance decreased while blood flow velocity and volumic blood flow did not increase significantly. In the common carotid artery circulation, diameter, mean blood flow did not change. However, vascular resistance and tangential tension decreased slightly. The increase in heart rate was strongly and negatively correlated (r = 0.82 p less than 0.01) with the change in the carotid artery tangential tension (measured as the product between mean arterial pressure and arterial radius) while no comparable correlation was observed with the change in blood pressure or arterial radius alone. The study suggested that in essential hypertensives, modifications in the carotid artery tangential tension secondary to arteriolar vasodilatation contribute actively to the baroreflex response.

[Central cardiovascular effects of a calcium inhibitor, nifedipine, and a calcium channel activator, Bay k 8644, in the anesthetized rat]

The antihypertensive effect of calcium channel inhibitors (CCI) results mainly from their direct action on the vascular smooth muscle. However CCI may pass through the blood-brain barrier and may modulate central mechanisms involving calcium channels. Normotensive (WKY) and spontaneously hypertensive (SHR) (Okamoto) rats weighing 300 g were anaesthetized with pentobarbital (50 mg/kg i.p.) and ventilated. Mean arterial pressure (MAP) was measured from a catheter inserted into the femoral artery. Heart rate (HR) was electronically integrated. Vehicle (ethanol 95%), nifedipine and Bay k 8644 (Bay) were injected under a 1.5 microliter volume into the lateral ventricle of the brain (i.c.v.). Vehicle alone did not change significantly MAP or HR. The calcium-channel inhibitor nifedipine and the calcium-channel activator Bay had opposite effects, when i.c.v. injected: hypotension with bradycardia and hypertension without tachycardia, respectively. These effects are dose-dependent (5-50 micrograms/kg). They are of central origin since they are suppressed by ganglionic blockade by hexamethonium(100 mg/kg i.c.). Bilateral vagotomy suppressed the i.c.v.-nifedipine induced bradycardia. Previously i.c.v. administered nifedipine (5 micrograms/kg) suppressed the pressor response to Bay (5 micrograms/kg i.c.v.). Changes in MAP and HR are significantly more marked in SHR than in WKY. These results indicate that a calcium-channel inhibitor and a calcium-channel activator can modulate in opposite fashion central calcium-dependent mechanisms involved in blood pressure control.

Enkephalins increase cyclic adenosine monophosphate content, calcium uptake, and contractile state in cultured chick embryo heart cells

Peripheral vascular effects of opioid peptides are well known, but direct myocardial effects have not been established. We studied the inotropic response of spontaneously beating cultured chick embryo ventricular cells to the enkephalin analogue [D-Ala2]-enkephalin. Amplitude of cell motion increased in a concentration-dependent manner with 0.53 microM [D-Ala2]-enkephalin producing half-maximal response. The mechanism of this positive inotropic effect was investigated by examining alterations in 45Ca influx, cyclic AMP accumulation and adenylate cyclase activity in response to [D-Ala2]-enkephalin. At maximally inotropic concentrations, the 45Ca influx rate increased 39%, adenylate cyclase was stimulated by 30%, and cyclic AMP content rose more than twofold. Thus, in contrast to neural tissue, receptors for enkephalin in cultured heart cells are coupled to adenylate cyclase in a stimulatory manner. Occupancy of these receptors produces an increase in cyclic AMP levels and exerts a positive inotropic effect via a verapamil-sensitive enhancement of Ca influx.

Common carotid blood flow in patients with hypertension and stenosis of the internal carotid artery

Common carotid blood flow has been measured using pulsed Doppler techniques in hypertensive patients over 45 years of age, with and without stenosis of the internal carotid artery. In hypertensive patients without stenosis, arterial diameter remained within the normal range, whereas blood flow velocity and blood flow were significantly reduced. Vascular resistance was significantly increased but did not change markedly after administration of the vasodilating drug isosorbid dinitrate. Patients with hypertension and stenosis of the internal carotid artery were compared with two different populations used as controls: In comparison with hypertensive patients without stenosis of the internal carotid artery, both arterial diameter and blood flow velocity were reduced, leading to a more pronounced decrease in blood flow; and in comparison with normotensive patients with stenosis of the internal carotid artery, common carotid blood flow was more reduced at any degree of stenosis. In a subset of patients, blood flow returned toward normal ranges after endarterectomy. The study suggested that in patients with hypertension without stenosis of the internal carotid artery, the decrease in blood flow is due to a decrease in blood flow velocity with normal arterial diameter despite the elevated blood pressure, and in patients with hypertension and stenosis of the internal carotid artery, blood flow was more reduced than in the normotensive patients with stenosis of the internal carotid artery, suggesting that caution must be taken with indications of antihypertensive treatment.

Inotropic effect, binding properties, and calcium flux effects of the calcium channel agonist CGP 28392 in intact cultured embryonic chick ventricular cells

CGP 28392 is a recently described dihydropyridine derivative with positive inotropic properties. To study the mechanism of action of this putative calcium channel agonist, we have related the effects of CGP 28392 on contraction (measured with an optical video system) and radioactive calcium uptake to ligand-binding studies in cultured, spontaneously beating chick embryo ventricular cells. CGP 28392 produced a concentration-dependent increase in amplitude and velocity of contraction (EC50 = 2 X 10(-7) M; maximum contractile effect = 85% of the calcium 3.6 mM response). Nifedipine produced a shift to the right of the concentration-effect curve for CGP 28392 without decreasing the maximum contractile response, suggesting competitive antagonism (pA2 = 8.3). Computer analysis of displacement of [3H]nitrendipine binding to intact heart cells by unlabeled CGP 28392 indicated a KD = 2.2 +/- 0.95 X 10(-7) M, in good agreement with the EC50 for the inotropic effect. CGP 28392 increased the rate of radioactive calcium influx (+39% at 10 seconds) without altering beating rate, while nifedipine decreased radioactive calcium influx and antagonized the CGP 28392-induced increase in calcium influx. Our results indicate that, in intact cultured myocytes, CGP 28392 acts as a calcium channel agonist and competes for the dihydropyridine-binding site of the slow calcium channel. In contrast to calcium channel blockers, CGP 28392 increases calcium influx and enhances the contractile state.

Central cardiovascular effects of kappa agonists dynorphin-(1-13) and ethylketocyclazocine in the anaesthetized rat

Opiate kappa agonists were administered into the cisterna magna of normotensive urethane-anaesthetized artificially ventilated rats: ethylketocyclazocine (78.7 nM) (EKC) and dynorphin-(1-13) (62.3 nM) produced significant and long-lasting decreases in both blood pressure and heart rate. High doses of naloxone (1 mg/kg i.v.) were required to partially antagonize these effects. The central cardiovascular effects of EKC and dynorphin-(1-13) were compared to those of fentanyl (3 nM), [D-Ala2,Met5]enkephalinamide (17 nM) and beta-endorphin (2.9 nM) which induced increases in blood pressure and heart rate. These results suggest that opposite central cardiovascular effects could be induced by activation of various opiate receptors.

[Hemodynamic and coronary effects of molsidomine in patients with stable coronary insufficiency in the basal state, during an atrial stimulation test and a cold test]

The heart rate (HR), the cardiac output (Qc) and the coronary sinus flow rate (Qcs), the left ventricular systolic and end-diastolic pressures (LVSP, LVEDP), the femoral artery pressure (FAP) and the difference between the coronary arterial and coronary venous oxygen tension (DAVcO2) were measured in patients with stable coronary insufficiency without cardiac failure, before and 40 to 60 minutes after 2 or 3 mg of molsidomine (M). In 20 patients, these measurements were made in the basal state, in spontaneous rhythm (SP). In 8 of these patient, (including 3 receiving beta-blockers) the measurements were made during an atrial stimulation test (ST) and in 8 other patients, all receiving long-term beta-blocker therapy, the measurements were made during a cold test (CT). At the basal state in SR, a gradual reduction in the LVSP to 70% or less of its initial value was observed in the patients receiving 3 mg of M (2 of whom received beta-blocker treatment). The LVSP was immediately restored by vascular filling. In 16 patients, M decreased the LVSP, the LVEDP, the FAP, the Qc and the double product (DP = LVSP X HR). The DAVcO2 was unchanged. Qcs and MVO2 (MVO2 = Qcs X DAVcO2) were decreased. In the course of ST, the haemodynamic and coronary changes are similar to those seen in the basal state. During the Ct, the increase in the LVSP, FAP and DP was significantly reduced by M. The variations in Qcs and coronary resistance (FAP/Qcs) were also significantly different after M., with better metabolic regulation of the coronary circulation.(ABSTRACT TRUNCATED AT 250 WORDS)

Opposite central cardiovascular effects of various morphine-like drugs and opiate peptides in the rat

Opiate agonists were administered into the cisterna magna of normotensive urethane-anaesthetized artificially-ventilated rats. Increases in blood pressure and heart rate were produced by fentanyl (0.3-3.0 nmol). [D-ala]2-met-enkephalinamide (17 nmol), and beta-endorphin (2.9 nmol). On the contrary, ethylketocyclazocine (78.7 nmol) and dynorphin (1-13) (62.3 nmol) produced decreases in blood pressure and heart rate. The cardiovascular effects of ethylketocyclazocine and dynorphin (1-13) were antagonized by higher doses of naloxone than that required to counteract the effects of fentanyl. These results suggest that opposite central cardiovascular effects could be induced by activation of various opiate receptors.

A new enkephalin analogue: trans-4-hydroxycinnamoyl-glycyl-glycyl-phenylalanyl-leucine. Synthesis and biological properties

A new analogue of the leucine-enkephalin in which the N-terminal tyrosine has been replaced by trans-4-hydroxycinnamic acid, has been synthetized by liquid-phase coupling methods. The central cardiovascular effects of this analogue were investigated and the results discussed.

Estimation of forearm arterial compliance in normal and hypertensive men from simultaneous pressure and flow measurements in the brachial artery, using a pulsed Doppler device and a first-order arterial model during diastole

Simultaneous brachial artery pressure and blood flow measurements were made in 45 men. Blood flow was evaluated by means of a pulsed Doppler device with a double transducer probe. From analysis of the pressure-flow curves during diastole, forearm arterial compliance (FAC) was determined by using the model of the forearm arterial tree as a system of tubes, each with a storage capacitance, in series with the arteriolar resistances vessels. The value of FAC for seven normal subjects, aged 44 +/- 3 (mean +/- SEM) years, was between 0.78 and 1.73 X 10(-10) m5 . N-1. By comparison, a 30% reduction in FAC was observed in 38 men of the same age with essential hypertension, which was similar whether the intra-arterial diastolic pressure was above or below 90 mmHg. In the more severe group (Intra arterial diastolic pressure greater than 90 mmHg), the reduced FAC was associated with a significant increase in brachial artery diameter; after administration of dihydralazine, blood pressure and arterial diameter returned to normal but FAC remained diminished. The study is the first to evaluate FAC in intact men. The reduced FAC in hypertension is independent of blood pressure "per se" but may reflect adaptive change in the walls of the large arteries. In the more severe hypertension, arterial calibre was increased; this could be a mechanism which could prevent FAC from decreasing further with chronic elevation of blood pressure.

[Anesthesia with continuous infusion of alfatesine and phenoperidine. Uses in anesthesia of aged subjects in visceral surgery]

Anaesthesia was administered to one hundred and fifty eight patients by continuous infusion of a mixture of Alfatesine and phenoperidine. The patients were divided on two groups: group A consisted in 96 patients undergoing abdominal surgery and group B of 62 cases of various types of surgery, mainly orthopedics. The average age was 63 years (range 16-96). The operative risk scored 6 or more in 71 cases. The length of operation averaged 151 minutes (S.D. +/- 15). The mixture made of alfadione 25 ml and phenoperidine 5 mg in a glucose 5 per cent 250 ml solution was administered by mechanical pump. The induction dose was 50 ml of the mixture for patients under 50 years (rate 10 ml per minute), 40 ml per patients from 50 to 70 years (5 ml per minute), and 30 ml for patients over 70 years (5 ml per minute). The maintenance dose was adjusted to weight and age and ranged from 0,11 to 0,15 ml/kg/h for alfadione and from 0,022 to 0,030 mg/kg/h for phenoperidine. Routine tracheal intubation and artificial ventilation were performed in group A. The results are studied in relation to the effectiveness of the anaesthesia mixture, its side effects and influence on recovery. Generally, the results are good and emphasize the value of the technic in abdominal surgery for elderly patients. The methods of application are discussed in terms of medical background.

[Effect of prolonged glucidic starvation on the contents of starch and tannins of Blechnum brasiliense L. gametophytes]

Some Blechnum brasiliense gametophytes have been maintained in darkness, in a purely mineral medium, for the purpose of investigating the effect of prolonged glucidic starving on the amount of tannins and starch that they contain. During the first two months the tannin contents undergoes a fast decrease. The starch variations are different : a transitory increase simultaneous with the fall in tannin; a decrease after the disappearance of 3/4 of the tannin contents; and lastly, a new amylogenese which precedes the prothallus necrosis. It seems that the gametophytes, in order to survive, degrade first their tannoidic reserves, and they utilize the starch that they contain only with difficulty. This behaviour can be explained by the distribution of the two metabolites; by the acid pH of the medium, which is not very propitious to the phosphorylases activity and lastly by the presence of chlorogenic acids, which are inhibitors of those enzymes.

[Comparative study of different extraction methods and assays of tannins in some pteridophytes]

Various processes of extraction and quantitative analysis of a condensed tannin in a plant extract, which also includes some chlorogenic acids, have been examined. 60% methanol, at 50 degrees C, proved the most efficient extraction solvent. Several methods of analysis have been tried. The measure of the colour intensity obtained by the action of sulphuric vanilline on flavanols cannot be used because it depends on the tannin condensation stage. It is impossible to separate tannin from chlorogenic acids using the methods of adsorption by skin or nylon powders, or precipitation by polyvinylpyrrolidone. Only paper chromatography, followed by the distinct elution of the various phenolic compounds, allows the tannin evaluation by subtraction; but owing to the variability of the results, many more experiments are necessary. Some other processes are being studied.

[Anesthesia in reoperations in abdominal surgery]

Fifty one patients from different surgical units, hence anesthetized by different anaesthesists, underwent reinterventions in abdominal surgery. The indications for the first intervention essentially involved the supra-mesocolic region of the abdomen (62 out of 100 cases). The operative risk during the first intervention was on the average 18 pour cent. The protocol of the first anaesthesia which was known in 42 cases, was of the narco-ataralgestic type. The date of the return to the operation table varied from 1 to 60 days. The state of the patients was in general catastrophic (organic renal failure, acute respiratory failure). Here again the anaesthesia was of the narco-ataralgesic type but the choice of drugs varied depending on the patients' state. However non significant difference was noted in the average hourly drug consumption between the two interventions. Apart from one circulatory arrest during induction, in one patient with hemorrhagic shock, no death was attributable to the anesthetic technique. The authors, using these findings, attempt to pick out a practical line of behaviour.