antagonism

…antihypertensive drugs, the AT1 receptor antagonists, was developed. Agonists are drugs or naturally occurring substances that activate physiologic receptors, whereas antagonists are drugs that block those receptors. In this case, angiotensin II is an agonist at AT1 receptors, and the antihypertensive AT1 drugs are antagonists. Antihypertensives illustrate the value of…

Important antagonistic relationships between certain mineral nutrients also are known. A large excess of rubidium, for example, interferes with the utilization of potassium in some lactic-acid bacteria; zinc can interfere with manganese utilization in the same organism. In animal nutrition, excessive molybdenum or zinc (both of…

Many examples of amino acid antagonism, in which inhibition of growth by one amino acid is counteracted by another amino acid, are best explained by this mechanism. For example, under some conditions Lactobacillus casei requires both D- and L-alanine, which differ from each other only in the position of the…

…an agonist or as an antagonist. A drug whose efficacy and affinity are sufficient for it to be able to bind to a receptor and affect cell function is an agonist. A drug with the affinity to bind to a receptor but without the efficacy to elicit a response is…

…transmit signal information, or as antagonists, which inhibit, or prevent, the receptor from transmitting information. Antagonists can compete with agonists and thereby block an agonist’s action. As therapeutic agents, both agonists and antagonists have been useful. For example, the hormone adrenaline (epinephrine) increases blood pressure by activating beta-adrenergic receptors, which…