Activation of cardiac beta 2 adrenoceptors in the human heart.
Comparative pharmacologic studies have indicated that the cardiac beta 2 adrenoceptors of vertebrate species are "adrenaline" receptors; i.e., the distribution of beta 2 receptors in the heart seems to be related to the amounts of adrenaline in the sympathetic nerves and in the circulation, and the beta 2 receptors seem to be stimulated mainly by adrenaline. In the human right atrium the order of potency for the agonists and the blocking agents indicate a relatively high proportion of active beta 2 receptors. These findings are in agreement with radioligand binding studies demonstrating up to 50% beta 2 receptors in myocardial membrane preparations. The pharmacologic studies thus add support to the assumption that these beta 2 receptors are functionally active and not merely experimental oddities. It is hypothesized that in normal situations the beta 2-receptor effects are additive to the beta 1 effects. However, during acute stress situations the large amounts of released adrenaline are assumed to increase markedly both inotropy and chronotropy in the heart via beta 2 receptors. It is postulated that only unselective beta blockers can abolish all beta-receptor effects in the heart during stress reactions with profound catecholamine stimulation.
Stene-Larsen
G
G
Ask
J A
JA
Helle
K B
KB
Fin
R
R
D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D000319:Adrenergic beta-Antagonists / Q000494:pharmacology; D000328:Adult; D000368:Aged; D000818:Animals; D001001:Anura; D002675:Child, Preschool; D004837:Epinephrine / Q000494:pharmacology; D006321:Heart / Q000187:drug effects*; D006801:Humans; D009200:Myocardial Contraction / Q000187:drug effects; D009638:Norepinephrine / Q000494:pharmacology; D051381:Rats; D011943:Receptors, Adrenergic, beta / Q000187:drug effects*; D014337:Trout
D000318:Adrenergic beta-Agonists; D000319:Adrenergic beta-Antagonists; D011943:Receptors, Adrenergic, beta; D009638:Norepinephrine; D004837:Epinephrine