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Biomedical subjects

A Zanchetti

Publications and source records attributed to A Zanchetti.

At least 397 records · Page 22Linked to original sources
PubMed1981

Carotid sinus reflex control of renin release in hypertensive subjects with high renin secretion.

1. Carotid baroreceptor manipulation (neck-chamber technique) and passive head-up tilting were used in ten patients with renovascular hypertension and in five subjects with essential hypertension under diuretic treatment to study reflex control of renin secretion at high basal-renin production rates. 2. Reflex effects of carotid baroreceptor manipulation on renin secretion were only minor. During baroreceptor deactivation there was a moderate increase in mean arterial pressure, but an inconsistent change in the renal venous--arterial difference in plasma renin activity (PRA). 3. During baroreceptor stimulation there was a modest fall in mean arterial pressure and a marked rise in the renal venous--arterial difference in PRA. This was opposite to the fall which might have been predicted as a result of the sympathetic depressor influence of the baroreceptor stimulus. Conversely, tilting increased the venous--arterial PRA difference by about 200%. 4. It is concluded that when renin production rate is high carotid baroreceptors exert little control over renin release, just as when renin production is low. Reflex control of renin, however, is very active in subjects with a high renin production, probably due to receptors in the cardiopulmonary region.

Adult↗
PubMed1981

Alpha 1-Adrenoceptor blockade: dissociation of its effects on renin release and arterial blood pressure in man.

1. The possibility that the juxtaglomerular alpha 1-adrenoceptors mediate an inhibitory action on renin release in man was examined in seven patients with essential hypertension, by measuring (i) the acute effects of prazosin (0.25 mg intravenously), a selective alpha 1-adrenoceptor-blocking agent, on arterial pressure and plasma renin activity, the degree of alpha-blockade induced by the drug being assessed by comparing the pressor response with that to a test dose of phenylephrine before and after prazosin administration, and (ii) the increases in plasma renin activity in response to isoprenaline before and during the prazosin-induced alpha-blockade. 2. Twenty minutes after the infusion of prazosin, when the pressor response to phenylephrine was reduced by 80% with respect to control, (i) mean arterial pressure was practically unchanged, (ii) plasma renin activity was almost doubled and (iii) the increases in plasma renin activity in response to isoprenaline were significantly greater, both in absolute and percentage values, than those observed before prazosin. 3. The increments in baseline plasma renin activity induced by prazosin in the absence of decrease in arterial pressure and the enhancement in renin responsiveness to the beta-adrenoceptor stimulus suggest that, in man, the juxtaglomerular alpha 1-adrenoceptors exert a direct, suppressive action on renin release.

Adolescent↗
PubMed1981

Role of sinoaortic reflexes in hemodynamic patterns of natural defense behaviors in the cat.

To evaluate whether sinoaortic afferents contribute to the hemodynamic pattern of fighting, cardiovascular changes associated with fighting were studied in cats before and after sinoaortic denervation. Sinoaortic denervation exaggerates the decrease in heart rate, cardiac output, and arterial pressure during immobile confrontation (hissing, staring but no movement). During nonsupportive fighting (fighting with forelimbs while lying on one side) and supportive fighting ( fighting while standing on four feet) sinoaortic denervation reduces the increase in heart rate and cardiac output, minimizes the mesenteric vasoconstriction, induces a fall in arterial blood pressure, but does not affect iliac vasoconstriction or vasodilatation. The hemodynamic pattern of fighting is similarly changed by temporary inactivation of carotid sinus baroreflexes by common carotid occlusion as by chronic section of sinoaortic nerves. It is concluded that sinoaortic reflexes play an important role in the cardiovascular patterns accompanying natural fighting. They favor cardiac action and allow a marked visceral vasoconstriction to occur, thus minimizing or preventing a fall in blood pressure during emotional behavior.

Aggression↗
PubMed1980

Time-course of the anti-hypertensive action of atenolol: comparison of response to first dose and to maintained oral administration.

To show whether repeated administration of atenolol for several days would influence its pharmacokinetic parameters and the extent and duration of the pharmacologic responses, the plasma level of atenolol and changes in heart rate, blood pressure and plasma renin activity were measured in 12 hypertensive patients at various times of day (9 a. m., 12 noon, 3 p. m. and 7 p. m.) after oral administration of the first dose of atenolol 100 mg, again during the 7th and 14th days of continued once-daily administration of the same dose, and finally during the three days following withdrawal of the drug. The peak plasma concentration of atenolol (about 600 ng/ml) was found 3 h after administration of the first dose, and measurable amounts (50-70 ng/ml) were found after 24 h. None of the pharmacokinetic characteristics were changed by administration of a single daily dose for two weeks. After withdrawal of the drug, detectable amounts of atenolol were found in plasma for at least 48 h. The first dose of atenolol caused prompt (3 h) and prolonged (up to 24 h) lowering of supine and standing systolic and diastolic blood pressures, slowing of supine and standing heart rate, reduction of the blood pressure and heart rate responses to dynamic exercise, and a decrease in plasma renin activity. The extent and time-course of all these responses were not influenced by repeated once-daily administration of the 100 mg dose for two weeks. Most of the effects continued during the withdrawal days, the lowering of blood pressure being somewhat more prolonged than the slowing of heart rate. It is concluded that a once-daily dose of atenolol 100 mg decreases blood pressure and heart rate throughout the following 24 h, without excessive daily fluctuation in its effects, and without signs of tolerance or accumulation.

Administration, Oral↗
PubMed1980

Antihypertensive and renal effects of orally administered verapamil.

In 12 in-patients with moderate uncomplicated hypertension, maintained on constant sodium intake for 15 days, single-blind oral administration of verapamil 80-160 mg t.i.d. for 10 days had a significant antihypertensive effect: in the supine position systolic blood pressure decreased from 177 +/- 5 to 150 +/- 3 mmHg, and diastolic pressure from 111 +/- 3 to 96 +/- 2 mmHg; standing values were similarly lowered from 171 +/- 7 to 143 +/- 4 mmHg, systolic, and from 118 +/- 4 to 97 +/- 2 mmHg, diastolic. The heart rate did not show any significant change (from 79 +/- 3 to 77 +/- 2 beats/min, supine, and from 92 +/- 3 to 87 +/- 3 beats/min, upright). The antihypertensive effect was uniform throughout the day, being similar 2, 3, 6 and 8 h after administration of a dose. Dynamic exercise (75-100 watts on a cycle-ergometer) caused identical increases in arterial pressure and heart rate on the last day of placebo and again on the last day with verapamil, but the peak levels of systolic pressure reached during exercise were lower after verapamil than with placebo, because of the lower blood pressure before exercise. Reduction of arterial pressure by verapamil was not accompanied by increased plasma renin activity, or by renal retention of sodium and water: there was a small increase in sodium excretion, at least during the first days of verapamil administration (from 107 +/- 15 to 113 +/- 15 mEq Na+/day), and a slight significant reduction in body weight (from 74.2 +/- 3.7 to 73.5 +/- 3.7 kg). It is concluded that oral administration of verapamil significantly lowers blood pressure without simultaneously inducing cardiac stimulation, renin secretion or salt and water retention.

Adult↗
PubMed1980

Blood pressure variability in man: its relation to high blood pressure, age and baroreflex sensitivity.

1. Intra-arterial blood pressure and heart rate were recorded for 24 h in ambulant hospitalized patients of variable age who had normal blood pressure or essential hypertension. Mean 24 h values, standard deviations and variation coefficient were obtained as the averages of values separately analysed for 48 consecutive half-hour periods. 2. In older subjects standard deviation and variation coefficient for mean arterial pressure were greater than in younger subjects with similar pressure values, whereas standard deviation and variation coefficient for mean arterial pressure were greater than in younger subjects with similar pressure values, whereas standard deviation aations and variation coefficient were obtained as the averages of values separately analysed for 48 consecurive half-hour periods. 2. In older subjects standard deviation and variation coefficient for mean arterial pressure were greater than in younger subjects with similar pressure values, whereas standard deviation and variation coefficient for heart rate were smaller. 3. In hypertensive subjects standard deviation for mean arterial pressure was greater than in normotensive subjects of similar ages, but this was not the case for variation coefficient, which was slightly smaller in the former than in the latter group. Normotensive and hypertensive subjects showed no difference in standard deviation and variation coefficient for heart rate. 4. In both normotensive and hypertensive subjects standard deviation and even more so variation coefficient were slightly or not related to arterial baroreflex sensitivity as measured by various methods (phenylephrine, neck suction etc.). 5. It is concluded that blood pressure variability increases and heart rate variability decreases with age, but that changes in variability are not so obvious in hypertension. Also, differences in variability among subjects are only marginally explained by differences in baroreflex function.

Adult↗
PubMed1980

Dose-response curve and time course of the antihypertensive effect of SKF 92 657, a beta-receptor-blocking and vasodilating compound.

1. The antihypertensive effect of the new drug, SKF 92 657, a hydrazinopyridazine derivative, possessing both beta-adrenoreceptor-blocking and vasodilating properties, was investigated in essential hypertension. 2. Single oral doses of 1.0 or 2.0 mg/kg did not produce any consistent decrease in blood pressure; 4.0 mg/kg was the threshold dose for a mild but not significant blood pressure reduction, whereas 8.0 mg/kg caused a significant and marked blood pressure decrease without clinically relevant changes in heart rate. 3. Continued administration of the drug for 7 days induced a significant and uniform reduction in blood pressure without tachycardia. The increase in systolic blood pressure and in heart rate caused by dynamic exercise was left unaffected by the drug.

Adrenergic beta-Antagonists↗
PubMed1979

Overview of cardiovascular reflexes in hypertension.

The problem of cardiovascular reflexes in hypertension poses several questions. The first is whether alterations in cardiovascular reflexes can initiate a persistent increase in arterial pressure. Another is whether it is an alteration in depressor or in pressor reflexes that matters in hypertension. Other questions concern the type and nature of the reflex alterations that actually occur in hypertension and the place of resetting of baroreflexes in the sequence of physiologic events leading to increased blood pressure.

Animals↗