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Biomedical subjects

B Waeber

Publications and source records attributed to B Waeber.

At least 253 records · Page 14Linked to original sources
PubMed1988

Individual responses to converting enzyme inhibitors and calcium antagonists.

This study was designed to assess whether the acute blood pressure response of an individual hypertensive patient to a calcium antagonist or an angiotensin converting enzyme (ACE) inhibitor is a good predictor of the long-term efficacy of these drug classes in this particular patient. The concept that good responses to ACE inhibitors and calcium antagonists may be mutually exclusive was also tested. Sixteen patients were included in a randomized crossover trial of enalapril, 20 mg daily, and diltiazem, 120 mg daily, for 6 weeks each. Blood pressure was measured by ambulatory blood pressure recording. During the washout phase, the acute effect of nifedipine, 10 mg p.o., and enalaprilat, 5 mg i.v., was evaluated. Nifedipine and enalaprilat reduced blood pressure equally well. The long-term blood pressure reduction induced by enalapril and diltiazem was similar. The acute blood pressure response to a given drug was not a good predictor of the result obtained with long-term therapy. No age dependency of the antihypertensive effect of either drug class was apparent. There was no evidence that a good response to one drug excluded a similarly good response to the other.

Adult↗
PubMed1988

Neuropeptide Y prevents the blood pressure fall induced by endotoxin in conscious rats with adrenal medullectomy.

Neuropeptide Y (NPY) is a vasoconstrictor peptide known to be present in the adrenal medulla, the terminal nerve endings, and in plasma. This study was designed to test whether NPY could prevent the acute blood pressure fall induced by endotoxin administration. Normotensive rats were subjected to adrenal demedullation on the right side and were either adrenalectomized or sham-operated on the left side. Eight to ten days later, NPY (0.07 microgram/min i.v.) or its vehicle were infused for 95 minutes into these conscious, semirestrained rats. The same experiments were performed with rats that received an infusion of epinephrine (0.1 microgram/min). These doses of NPY and epinephrine when given alone had no blood pressure effect. During the last 75 minutes of the 95-minute infusion, endotoxin (lipopolysaccharide Escherichia coli 0.111:B4, 10 micrograms/min i.v.) or its vehicle were administered. In rats with an intact adrenal gland, endotoxin failed to induce hypotension. In rats lacking a functioning adrenal medulla, however, endotoxin induced a pronounced mean blood pressure fall of 55 +/- 11.6 mm Hg (mean +/- SEM). This blood pressure drop could be prevented equally well with NPY and with epinephrine infusion and averaged 11 +/- 2.3 and 16 +/- 2.4 mm Hg, respectively, at the end of the experiment. Additional rats were biadrenalectomized and supplemented with an excess of glucocorticoids and mineralocorticoids. In these rats also, NPY markedly attenuated the blood pressure fall resulting from endotoxemia. These data taken together indicate that in conscious rats with no adrenal medulla, the acute blood pressure fall induced by endotoxin administration is greatly enhanced.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenal Medulla↗
PubMed1988

Hypotensive effect of the active fragment derived from factor XII is mediated by an activation of the plasma kallikrein-kinin system.

Plasma protein fraction (PPF) contaminated by factor XII active fragment (XIIf) may cause hypotensive reactions when infused to patients. This study was planned to assess in conscious normotensive rats whether the blood pressure response to the factor XIIf is mediated by an activation of the plasma kallikrein-kinin system or by stimulation of prostaglandin synthesis. To test whether the factor XIIf-induced blood pressure fall is due partially to an enhanced generation of vasodilating prostaglandins, the blood pressure effect of XIIf (1 microgram i.v.) was investigated 15 min after treatment with indomethacin (5 mg i.v.), an inhibitor of cyclo-oxygenase. Factor XIIf reduced mean blood pressure similarly in indomethacin- and vehicle-treated rats (-23 +/- 4 mmHg, n = 5, and -23 +/- 5 mmHg, n = 4, respectively). Other rats received factor XIIf 15 min after depletion of circulating prekallikrein by the administration of dextran sulfate. Thirty minutes after a 0.25 mg i.v. dose of this agent, plasma prekallikrein activity averaged 0.12 +/- 0.015 mumol/min/ml (n = 6) as compared to 2.48 +/- 0.31 mumol/min/ml in control rats (n = 4, P less than .001). Factor XIIf decreased mean blood pressure by only 4 +/- 2 mm Hg in rats pretreated with dextran sulfate. Thus, it was possible to blunt the acute hypotensive effect of factor XIIf by depleting circulating prekallikrein, but not by inhibiting prostaglandin production. This strongly suggests that the blood pressure effects of factor XIIf is mediated by a stimulation of the plasma kallikrein-kinin system.

Animals↗
PubMed1988

Enhanced urinary kallikrein excretion in response to a moderate sodium load in genetically hypertensive rats.

Experiments were performed to compare the diuretic and natriuretic response to a moderate saline load between 12-week-old conscious spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto (WKY) male rats. The animals were infused intravenously with 0.9% NaCl, first for a 1-h equilibration period, at a rate of 20 microliters/min, then for a 2-h salt-loading phase at 40 microliters/min, and finally during a 1-h recovery at 20 microliters/min. Cumulative renal excretion of water and sodium was similar in SHR and WKY rats. In contrast, urinary kallikrein excretion (amidolytic assay) during the saline-expansion and recovery phases was significantly higher in SHR than in WKY rats. At the end of the salt-loading phase, plasma levels of atrial natriuretic peptide (ANP) were higher in SHR than in WKY rats (p less than 0.05). This was also true in animals infused with 5% dextrose instead of 0.9% NaCl. Splanchnic nerve activity remained stable throughout the study in SHR as well as in WKY rats. These data therefore indicate that SHR excrete water and sodium similarly to WKY rats when they are subjected to a moderate sodium load. Neither ANP nor the sympathetic nervous system seems to be directly implicated in the renal response to the moderate saline expansion. Whether the enhanced urinary kallikrein excretion observed in SHR reflects an active participation of the renal kallikrein-kinin system in their sodium handling remains uncertain.

Animals↗
PubMed1988

Effects of neuropeptide Y on the blood pressure response to various vasoconstrictor agents.

Neuropeptide Y (NPY) is known to potentiate the pressor effect of norepinephrine. In the present work, we evaluated in unanesthetized normotensive rats the effect of NPY on blood pressure responsiveness not only to norepinephrine, but also to tyramine, a sympathomimetic agent acting indirectly to B-HT933, a selective alpha-2 adrenoceptor stimulant, to angiotensin II and vasopressin. Dose-response curves to the various pressor agents were established starting at the 45th min of an i.v. infusion with either NPY (0.025 and 0.1 microgram/min) or its vehicle. The two doses of NPY increased blood pressure by an average of approximately 6 mm Hg, which was not significantly different from the vehicle-induced blood pressure changes. NPY significantly enhanced the pressor effect of norepinephrine, tyramine and angiotensin II, but not that of B-HT933 and vasopressin. We also tested whether NPY inhibits the enzyme activity of Na, K-adenosine triphosphatase using a purified toad kidney preparation. Concentrations of NPY from 10(-14) M up to 10(-6) M had no effect on the enzyme activity. It appears therefore that the blood pressure potentiating effect of NPY is not restricted to alpha adrenoceptor stimulation with norepinephrine, but involves also the vasoconstrictor hormone angiotensin II. This NPY-induced potentiation does not seem to depend upon stimulation of alpha-2 adrenoceptors or inhibition of Na,K-adenosine triphosphatase.

Animals↗
PubMed1988

[Role of atrial natriuretic peptide in the renal response to acute volume expansion in the normal and essential hypertensive patient].

An exaggerated natriuretic response to volume expansion (VE) is observed in many essential hypertensive patients. The plasma levels of atrial natriuretic peptide (ANP) were measured in 11 normal subjects (NT) and 12 patients with mild essential hypertension (EH) during VE (1 800 ml isotonic saline IV over 3 hours). NT and EH groups were similar with respect to age and basal levels of renin, aldosterone and ANP (34.5 +/- 5.5 in NT and 32.5 +/- 6.3 pg/ml in EH, mean +/- sem). In response to VE, ANP increased to the same extent in both groups (a change of + 19.3 +/- 5.2 in NT and 22.2 +/- 7.1 pg/ml in EH) despite the marked difference in observed natriuresis (36 +/- 3.5 in NT and 54.9 +/- 6.3 mmol/3 in EH, p less than 0.02). The change in ANP induced by VE was inversely correlated with the fall in hematocrit and the variation in fractional excretion of sodium in both groups. These results suggest that atrial natriuretic peptide may participate in the control of the renal response to isotonic volume expansion, but they do not support a predominant role of atrial natriuretic peptide in the exaggerated natriuretic responses to volume expansion of patients with essential hypertension.

Adult↗
PubMed1988

[Arterial hypertension with hyperkalemia, tubular acidosis and normal renal function: Gordon syndrome and/or pseudohypoaldosteronism type II?].

Basic examination of Mr S., 45 years of age, short in stature and overweight (1.60 m, 76 kg), was carried out because of the mild hypertension (mean AP 125 mm Hg) from which he had suffered for 20 years. The results were as follows: (1) variable hyperkalemia: plasma potassium values were 5.3 to 6.9 mmol/l; (2) normal renal function: serum creatinine 91.5 mumol/l, clearance of inulin 136.6 ml/mn; (3) proximal tubular acidosis: plasma bicarbonate and chloride values were 18.4 and 109 mmol/l, respectively; urinary pH was 7.1 with negative H+ ions urinary excretion (-33 mumol/mn); when plasma bicarbonate level was raised to 26 mmol/l by acute loading, fractional excretion of bicarbonate increased to 19,5 p. 100 while plasma potassium value decreased to 4.2 mmol/l; (4) low PRA (0.29 ng/ml/h) and normal plasma aldosterone concentration (63 pg/ml) with a normal intake of sodium and in a recumbent position. Plasma atrial natriuretic factor (ANF) level was normal: 14 fmol/ml. Intravenous infusion of ANF for 2 h (1 microgram/mn) induced the expected increases in urinary flow rate, and sodium and potassium excretions (+226, +307 and +171 p. 100, respectively). Intravenous infusion of isotonic saline (2 l in 2 h) and oral administration of fludrocortisone acetate for 4 weeks (400 micrograms per day) resulted in a normal decrease in PRA and plasma aldosterone concentration, a normal rise in plasma ANF level (22 and 42 fmol/ml) while slightly increasing AP without improving bicarbonaturia and acidosis.(ABSTRACT TRUNCATED AT 250 WORDS)

Acidosis, Renal Tubular↗
PubMed1988

What we would like to know about the antihypertensive mechanisms of angiotensin converting enzyme inhibition.

Angiotensin converting enzyme (ACE) inhibitors induce haemodynamic, humoral and metabolic actions which have been well characterized during the last decade. The precise mechanisms involved in these actions still need clarification. Among the many questions we need answered are the following: under steady-state conditions, does plasma ACE activity reflect angiotensin I conversion in tissues? Do the low levels of angiotensin II observed after ACE inhibition still contribute to vascular tone? What is the precise role of extrarenal tissue renin in the regulation of vascular tone? What is the role of bradykinin, prostaglandins and the interaction with the sympathetic nervous system in the antihypertensive effect of ACE inhibition? We hope that definite answers to these questions will be found during the second decade of the use of ACE inhibitors.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1988

Effects of a nonpressor dose of neuropeptide Y on cardiac output, regional blood flow distribution and plasma renin, vasopressin and catecholamine levels.

Neuropeptide Y (NPY) is a peptide with vasoconstrictor properties known to be present in the central nervous system as well as in sympathetic nerve endings and the adrenal medulla. The purposes of this study were to investigate in normotensive conscious rats the effects of nonpressor doses of NPY on cardiac output and regional blood flow distribution (using radiolabeled microspheres) as well as on plasma renin activity, plasma catecholamine and vasopressin levels. NPY (0.1 microgram/min) infused i.v. for 30 min modified neither blood pressure nor heart rate. Cardiac index was at comparable levels in NPY- as in vehicle-treated rats (17.7 +/- 1.6, n = 8, vs. 21.3 +/- 0.9 ml/min/100 g, n = 8, mean +/- S.E.M.). There was no significant difference in regional blood flow distribution between the two groups of rats, except for the large intestine (0.42 +/- 0.06 vs. 0.71 +/- 0.1 ml/min/g in NPY- and vehicle-treated rats, respectively, P less than .05). Basal plasma renin activity and catecholamine levels were not modified by NPY whereas plasma vasopressin levels were lower (P less than .05) in rats given NPY (0.76 +/- 0.3 pg/ml, n = 8) than in those having received the vehicle (2.2 +/- 0.4 pg/ml).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Ambulatory blood pressure monitoring in the elderly hypertensive patient.

In this retrospective analysis, we assessed the usefulness of ambulatory blood pressure monitoring in the evaluation of elderly hypertensive patients. Thirty-eight untreated and 31 treated hypertensives aged 70 years or more had a systolic blood pressure greater than or equal to 160 mmHg and/or a diastolic blood pressure greater than or equal to 95 mmHg in the clinic. All 69 patients underwent blood pressure monitoring during their customary daily activities using a portable semi-automatic blood pressure recorder (Remier M2000). The mean of all blood pressures obtained with this device was taken as the ambulatory recorded blood pressure. Recorded blood pressures were greater than or equal to 160 mmHg systolic and greater than or equal to 90 mmHg diastolic in 17 untreated and 17 treated patients. In these patients, the introduction of antihypertensive therapy, or its modification, markedly reduced blood pressure during a 4-8 month follow-up. A further 21 untreated and 14 treated patients had recorded blood pressures of less than 160/90 mmHg. The treatment status of these patients was left unchanged for 4-8 months of follow-up. Nevertheless, office blood pressure in these groups, with no change in treatment, decreased significantly during the observation period. At the last visit to the outpatient clinic, there was no significant difference in blood pressure between the four subgroups of patients. Thus, ambulatory blood pressure monitoring appears to be useful in the elderly hypertensive patient in detecting those patients whose blood pressure is elevated only in the clinic. Blood pressure profiles obtained outside the clinic may therefore be useful in making therapeutic decisions in the aged hypertensive.

Activities of Daily Living↗
PubMed1988

Antihypertensive effect of diltiazem administered once and twice daily.

This study was undertaken to compare the antihypertensive effect of diltiazem administered once or twice daily. After a two week wash-out period, eight hypertensive patients were treated for two consecutive four week phases with 180 mg once daily or 90 mg twice daily of a sustained-release formulation of diltiazem. The sequence of the treatments was randomised and the trial carried out in a double-blind fashion. Ambulatory daytime BP profiles were obtained using a portable BP recorder (Remler M2000). The average of all BP readings taken during the monitoring period was 159/104 +/- 21/10 mgHg (mean +/- SD) at the end of the wash-out period and 145/90 +/- 20/12 and 148/95 +/- 21/11 mmHg under treatment with diltiazem 180 mg once daily and 90 mg twice daily, respectively. These data indicate that 180 mg of a slow-release formulation of diltiazem are as effective in lowering the BP of hypertensive patients when administered daily in a single dose as when divided into two doses.

Adult↗
PubMed1987

Markedly reduced blood pressure responsiveness in endotoxemic rats; reversal by neuropeptide Y.

This study in conscious normotensive rats was performed to assess the effect of the vasoconstrictor peptide, neuropeptide Y (NPY), on blood pressure responsiveness to exogenous norepinephrine in endotoxaemia. NPY and endotoxin were infused at doses which had no effect on blood pressure, whether given alone or in combination. Endotoxin markedly reduced the pressor responses to bolus injections of norepinephrine. However, blood pressure responsiveness could be enhanced by infusing NPY simultaneously with the endotoxin. It is suggested that low dose NPY infusions may be clinically useful in reversing the reduced vascular responsiveness to pressor amines in shock.

Adrenal Medulla↗
PubMed1987

[Clinical experiences with atrial natriuretic factor].

Myocardial cells of mammals release a peptide with diuretic, natriuretic and vasodilating properties into the circulation. This peptide, called atrial natriuretic factor, is also involved in the regulation of plasma volume and, in addition, is instrumental in suppressing the activity of the renin-angiotensin-aldosterone system. The renal effects of the atrial natriuretic factor become less pronounced when systemic blood pressure is lowered. The auricular natriuretic factor seems to play an important role in cardiovascular regulation due to both its renal and extrarenal actions.

Animals↗
PubMed1987

[Effect of atrial natriuretic factor on the hematocrit of patients in chronic hemodialysis].

A synthetic atrial natriuretic peptide (ANF) has been administered to 7 patients with chronic renal failure to evaluate the role of ANF in the regulation of blood volume. ANF (2 micrograms/min) was infused for 60 minutes before hemodialysis and blood pressure, heart rate, plasma proteins and hematocrit were measured at regular intervals. Although a slight decrease in blood pressure occurred during ANF infusion, no significant changes in hematocrit and plasma proteins were observed. These results suggest that administration of exogenous ANF does not modify the volume distribution in patients with chronic renal failure. ANF's lack of effect is perhaps due to the chronic hypervolemia and the high plasma levels of endogenous ANF commonly found in these patients.

Aged↗