Blood pressure and plasma noradrenaline during single high-dose beta adrenoceptor blockade

Factors affecting lipoprotein lipase in hypertensive patients

Arterial hypertension is frequently associated with serum lipid abnormalities. Lipid metabolism can also be affected by antihypertensive treatment, possibly via an interference with lipoprotein lipase (LPL) activity. The aims of this study were to investigate the metabolic and hemodynamic factors that can interfere with plasma postheparin LPL activity in a sample of 13 patients with mild, uncomplicated arterial hypertension. The effects of vasodilator administration (prazosin and hydralazine) alone or in combination with a beta-blocker (propranolol) were also studied. A direct correlation between serum insulin levels and LPL activity was found during placebo treatment. This was confirmed by multiple regression analysis, which also showed a positive correlation of LPL activity with aortic flow velocity and plasma adrenaline (F significance = 0.0007, R2 = .905). Serum insulin was also directly correlated with cholesterol in high-density lipoproteins (HDLs) and in the HDL2 subfraction. A significant decrease in LPL activity was observed during the addition of propranolol to vasodilators as compared with vasodilators alone. A positive correlation was found between LPL and adrenaline changes induced by the combined treatment. These data suggest that LPL may play a role in the pathophysiologic connections between insulin action, the adrenergic nervous system (ANS), and lipid metabolism.

Comparison of the haemodynamic effects of bucindolol, propranolol and pindolol in healthy volunteers

The effects of single oral doses of bucindolol (50, 100, 200 and 400 mg), pindolol (10 mg), propranolol (160 mg) and placebo on arterial pressure and heart rate in the supine and standing positions and exercise heart rate were compared in 12 healthy male volunteers. Supine heart rate was significantly greater after all four doses of bucindolol and pindolol in comparison to propranolol. Bucindolol had no significant effect on standing heart rate which was significantly reduced by pindolol and propranolol. Bucindolol, pindolol and propranolol significantly reduced an exercise tachycardia for at least 24 h after drug administration. Supine systolic pressure was not affected by any treatment but supine diastolic pressure was significantly reduced by bucindolol (200 and 400 mg) and by pindolol. All doses of bucindolol, propranolol and pindolol significantly reduced standing systolic blood pressure. There was a significant linear trend for reductions in standing systolic blood pressure and increasing doses of bucindolol. Standing diastolic blood pressure was significantly reduced by bucindolol 200 and 400 mg. Faintness and light headedness occurred in 6 of 12 subjects after 200 mg bucindolol and in 8 of 10 subjects after 400 bucindolol. After bucindolol, analysis of plasma samples demonstrated the presence of bucindolol, 5-hydroxy and 6-hydroxy bucindolol and indolyl-t-butylamine. These observations indicate that in man, bucindolol is a beta-adrenoceptor blocking drug with hypotensive activity and probably partial agonist activity. It is unlikely that the hypotensive effects result from blockade of beta-adrenoceptors or from the drug's partial agonist activity.

Antihypertensive effect and degree of beta-adrenoceptor blockade after short-term and semi-chronic propranolol therapy

In patients with normal-renin, mild (n = 6) or moderate (n = 6) hypertension, the antihypertensive effects of propranolol (80 mg/day) for 1 day or for 2 weeks were evaluated in relation to the degree of beta-adrenoceptor blockade induced. A significant and similar fall in systolic blood pressure was observed after 1 day and 2 weeks on propranolol in both groups of patients. In contrast, diastolic blood pressure showed only a minor decrease after 1 day of therapy (-2 +/- 2 and -3 +/- 1 mm Hg) but a significant drop (-7 +/- 3 and -9 +/- 3 mm Hg) after 2 weeks in the mild and moderate hypertension groups, respectively. Plasma propranolol levels and decreases in resting heart rate and PRA were similar after 1 day and 2 weeks of treatment. Isoprenaline dose-response curves for systolic and diastolic blood pressure, heart rate and PRA showed similar parallel shifts after 1 day and 2 weeks of treatment. The effect of graded bicycle exercise on these parameters were also similarly blunted. These results indicate that over time, systolic blood pressure decreases rapidly whereas diastolic blood pressure shows a delayed fall following initiation of low-dose propranolol therapy, despite the same degree of beta-adrenoceptor blockade.

Propranolol effects on autonomic function in hypertensive men

Beta blocker antihypertensive effects are incompletely understood, and may involve alterations in the autonomic nervous system. We studied autonomic function in 12 essential hypertensive men during treatment with placebo and chronic oral propranolol. Propranolol reduced blood pressure and heart rate (both p less than 0.01) with an associated increase in baroreflex sensitivity during phenylephrine testing (p less than 0.02), though amyl nitrite-tested baroreflex sensitivity was unchanged; blood pressure decrement did not correlate with baroreflex enhancement. Response to the cold pressor test and the blood pressure decrement to phentolamine alpha blockade were unaltered by propranolol, suggesting unchanged efferent sympathetic function; nor were several biochemical indices of sympathetic nervous activity influenced by propranolol. Propranolol does perturb autonomic function in man, but the perturbations do not correlate with blood pressure decrement; nor are physiologic or biochemical indices of efferent sympathetic activity reduced by propranolol.

The effect of different classes of beta-antagonists on clinical and experimental hypertension

The reference beta adrenoceptor antagonist propranolol reduces blood pressure in about 60% of patients with essential hypertension. Pressure is reduced in the supine, and erect positions without postural hypotension as well as during exercise. The average extent of pressure reduction is approximately 26/16 mm.Hg. Though all clinically available beta antagonists reduce blood pressure, the profile may be modified by both adrenotropic and non-adrenotropic ancillary properties. Of the adrenotropic properties, potency influences dose frequency and total body burden of drug. Selective beta 1 antagonism may enhance safety without reducing efficacy in patients with obstructive airways disease. Selective beta 2 blockade does not reduce blood pressure in experimental models or normal subjects, but the response in patients is unknown. Partial agonism may reduce efficacy if the degree of stimulant activity is too great. Of the non-adrenotropic properties, membrane stabilising properties are of relevance only in so far as such agents undergo extensive biotransformation resulting in either reduced efficacy when drugs are used at fixed doses or the formation of biologically active metabolites. The additional properties of either alpha adrenergic blockade or inhibition of vascular smooth muscle tone modify both the speed of onset and the haemodynamic profile. The interaction of these ancillary pharmacological properties is evaluated in this review.

Differential effects of DL-propranolol on norepinephrine in cerebrospinal fluid and plasma

Acute administration of DL-propranolol (5 mg/kg, subcutaneous) to cats caused a significant increase in cerebrospinal fluid (CSF) norepinephrine and a significant decrease in plasma norepinephrine. This increase in CSF norepinephrine is probably due to a reflex increase in central noradrenergic firing after beta blockade. The decrease in plasma norepinephrine reflects decreased sympathetic outflow. These results are consistent with the centrally mediated hypotensive effects of the drug.