Journal of cardiovascular pharmacology
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J. Cardiovasc. Pharmacol. · Jan 1984
A population study on the relationship between blood pressure and the excretion of urinary cations.
The relationships between blood pressure and the 24-h excretion of three urinary cations (Ca2+, K+, and Na+) were investigated in a random sample of 528 adults (greater than or equal to 20 years) inhabitants of two Belgian towns. In these adults both systolic and diastolic blood pressures were strongly and independently correlated with age and body weight. Systolic pressure in women was significantly and positively related to pulse rate. ⋯ In 56 current pill users there was a positive association between systolic pressure and 24-h urinary sodium (p less than 0.01 after adjusting for age, body weight, and pulse rate). The present study indicates that urinary potassium is a consistent and negative predictor of both systolic and diastolic pressures in adult men, whose diastolic pressure is weakly and positively associated with urinary calcium. The positive association between systolic pressure and urinary sodium in current users of contraceptive pills may suggest that their blood pressure becomes responsive to their usual salt intake.
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J. Cardiovasc. Pharmacol. · Sep 1983
Effects of intracisternal and intravenous alpha-methyldopa and clonidine on haemodynamics and baroreceptor--heart rate reflex properties in conscious rabbits.
We determined the doses of intracisternal (i.c.) and intravenous (i.v.) clonidine and alpha-methyldopa (alpha-MD) that produced near-maximal falls in mean arterial pressure (MAP) in conscious rabbits. We then studied the haemodynamic mechanisms underlying the fall in MAP and changes in the properties of the baroreceptor-heart rate reflex. Intracisternal and intravenous administration of both drugs lowered MAP by approximately 25% of control, and the fall was about half due to the reduction in cardiac output and about half due to a fall in total peripheral resistance. ⋯ These differences between drugs were still present with much larger i.c. doses. Our findings suggest that both drugs influence resting haemodynamics and the vagal component of the baroreflex through similar effects on the central autonomic pathways. But there are some differences in their central actions on cardiac sympathetic motoneurons.
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J. Cardiovasc. Pharmacol. · Jul 1982
Renal and cardiovascular responses to acute hypercapnic acidosis in conscious dogs: role of renin--angiotensin.
Patients with pulmonary dysfunction and CO2 retention have renal hemodynamic abnormalities accompanied by increased plasma renin activity. To determine if hypercapnia impairs renal function, particularly through the renin-angiotensin system, the effects of acute hypercapnic acidosis (HC), using 8.5% CO2, were measured in five unanesthetized dogs during (a) the intact state; (b) renin-angiotensin antagonism using either 1-sarcosine, 8-glycine angiotensin II ( [Sar1, Gly8] AII) or SQ 14,225; and (c) exogenous angiotensin II infusion. As partial arterial carbon dioxide pressure (PaCO2) increased (p less than 0.05) from control (C) of 35 +/- 1 (SEM) to 48 +/- 1 mm Hg during HC, arterial pH fell (p less than 0.05) from 7.36 +/- 0.01 to 7.24 +/- 0.005. ⋯ Although systemic vascular responses to exogenous AII infusion were similar, the renal vasoconstrictor response was antagonized during HC with unchanged GFR and renal blood flow. These findings indicate that despite activation of the renin-angiotensin system, acute hypercapnic acidosis is unassociated with impairment of renal function in unanesthetized dogs. This may be related to diminished renal vascular AII responsiveness during hypercapnia.
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J. Cardiovasc. Pharmacol. · Jul 1982
Lack of correlation of verapamil plasma level with cumulative protective effects against halothane--epinephrine ventricular arrhythmias.
The effect of verapamil, 0.2 mg/kg i.v. over 30 s, on the amount of epinephrine required to elicit a reproducible ventricular arrhythmia during 0.9% halothane in oxygen anesthesia was investigated in two groups of dogs after three consecutive doses of verapamil given at 90 (group I) and 120 min (group II) intervals, respectively. Verapamil caused a stepwise cumulative increase in the arrhythmogenic dose of epinephrine in both groups despite plasma verapamil levels that declined to low levels (28 and 22 ng/ml, respectively) between doses. ⋯ Changes in heart rate or blood pressure were similar among the three doses of verapamil in each group. These results can be interpreted to indicate that, unlike hemodynamic effects that appear to parallel plasma verapamil concentrations, the protective effects of verapamil against halothane--epinephrine ventricular arrhythmias may not be accurately reflected by plasma verapamil levels and may be significantly present when plasma levels are too low to cause measurable hemodynamic effects.
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J. Cardiovasc. Pharmacol. · Jan 1982
An oral calcium antagonist for treatment of hypertensive emergencies.
The efficacy and safety of 20 mg of nifedipine as a single oral dose have been studied with respect to the use of the drug as an alternative treatment of hypertensive emergencies. The study population consisted of nine male and nine female patients, 47 to 80 years old. ⋯ The fall of blood pressure was directly related to pretreatment values. Oral nifedipine can be recommended as a first-line drug to lower blood pressure in hypertensive emergencies.