Is there any evidence of beta 1-adrenoceptors mediating relaxation of guinea-pig lung parenchyma?
We tried to find functional evidence for the existence of beta 1- and beta 2-adrenoceptors in the isolated guinea-pig lung parenchymal strip preparation, using potent and selective beta 1- and beta 2-adrenoceptor stimulation. To obtain potent beta 1-adrenoceptor stimulation the nonselective beta-adrenoceptor agonist isoprenaline was combined with a highly selective beta 2-adrenoceptor antagonist--ICI 118,551. Potent beta 2-adrenoceptor stimulation was obtained by procaterol. Practolol (beta 1-adrenoceptor antagonist) and ICI 118,551 were used as antagonists. ICI 118,551, 10(-7) mol/l, shifted the concentration response (C/R) curve of isoprenaline to a higher concentration range. The C/R curve of procaterol was shifted in the same way and to the same degree by this concentration of ICI 118,551. The C/R curve of isoprenaline was not further shifted after blockade with a combination of ICI 118,551, 10(-7) mol/l, and practolol, 10(-6). However, in the trachea preparation, a tissue containing both beta 1- and beta 2-adrenoceptors, there was a further shift of the C/R curve of isoprenaline to a higher concentration range after blockade with a combination of ICI 118,551 and practolol in the concentrations given above. In this preparation the shift of the C/R curve of procaterol was ten times greater than that of isoprenaline after blockade with ICI 118,551, 10(-7) mol/l. We conclude that it is possible to characterize small fractions of beta 1-adrenoceptors coexisting with beta 2-adrenoceptors with the technique used. Furthermore there is still no functional evidence of the existence of beta 1-adrenoceptors in the lung parenchyma.
D000319:Adrenergic beta-Antagonists / Q000494:pharmacology; D000818:Animals; D004983:Ethanolamines / Q000494:pharmacology; D006168:Guinea Pigs; D066298:In Vitro Techniques; D007545:Isoproterenol / Q000494:pharmacology; D008168:Lung / Q000187:drug effects* / Q000378:metabolism; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects*; D009126:Muscle Relaxation / Q000187:drug effects*; D009130:Muscle, Smooth / Q000187:drug effects* / Q000378:metabolism; D017265:Procaterol; D011412:Propanolamines / Q000494:pharmacology; D011943:Receptors, Adrenergic, beta / Q000187:drug effects / Q000502:physiology*; D014132:Trachea / Q000187:drug effects / Q000378:metabolism
D000319:Adrenergic beta-Antagonists; D004983:Ethanolamines; D011412:Propanolamines; D011943:Receptors, Adrenergic, beta; C026777:ICI 118551; D007545:Isoproterenol; D017265:Procaterol