b-Adrenergic blockers are an import class of cardiovascular drugs and are select
ID: 3472885 • Letter: B
Question
b-Adrenergic blockers are an import class of cardiovascular drugs and are selective antagonists of b -adrenergic receptors that are linked to G-proteins. One potent class of b -blockers is Oxprenolol which is used in the treatment of hypertension, angina pectoris, arrhythmias, and anxiety. Given what you know regarding the role of b -receptors in signal transduction pathways involving endocrine and neurotransmitter signaling, describe the cellular, molecular and physiological effects of this drug.
How does this drug affect the sympathetic system? What effect does it have on the function of a cardiomyocyte?
Describe what would happen should a patient accidentally take a double dose of this medication? What effect would it have on the normal function of the heart?
Explanation / Answer
b-Adrenergic blockers are an import class of cardiovascular drugs and are selective antagonists of catecholamines.
1. beta1-adrenergic receptor associated with the heart increases the force and rate of myocardial contraction.
2) Beta antagonists block the ability of the sympathetic nervous system to increase the contractile force and the rate of contraction.
3) The release of renin from the kidney is also regulated by the beta1-receptor. By blocking renin secretion beta1 blockers reduce the formation and hence the biological activity of angiotensin II.
4) Beta1-receptor antagonists decrease blood pressure. While the mechanism underlying this effect is not completely understood, it certainly involves a decrease in cardiac output and heart rate as well as decreasing angiotensin II levels. This reduction in blood pressure makes the beta blockers useful in the treatment of hypertension.
5) Beta blockers are also useful in treating ischemic heart disease. This is because two major determinants of myocardial oxygen consumption are the force and rate of myocardial contraction which are diminished by this class of drugs.
6) Beta blockers are given following a myocardial infarction to prevent reinfarction.
7) Certain arrhythmias are due to excess stimulation of the beta1-receptors. Thus beta blockers are useful in treating supraventricular tachyarrhythmias.
.Beta blockers can attenuate cardiomyocyte apoptosis in heart failure.Beta blockers are competitive antagonists that block the receptor sites for the endogenous catecholamines epinephrine (adrenaline) and norepinephrine (noradrenaline) on adrenergic beta receptors, of the sympathetic nervous system, which mediates the fight-or-flight response.
Double dose of beta blockers would reduce the blodd pressure.
Beta-blockers bind to beta-adrenoceptors located in cardiac nodal tissue, the conducting system, and contracting myocytes. The heart has both 1 and 2 adrenoceptors, although the predominant receptor type in number and function is 1. These receptors primarily bind norepinephrine that is released from sympathetic adrenergic nerves. Additionally, they bind norepinephrine and epinephrine that circulate in the blood. Beta-blockers prevent the normal ligand (norepinephrine or epinephrine) from binding to the beta-adrenoceptor by competing for the binding site.
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