title: Age-related differences in the beta-adrenergic vasodilator response in rat aortic rings.
abstract: Mechanisms underlying age-dependent changes in vasodilator responses to beta-adrenergic drugs are poorly understood. The aim of the current study was to compare responses to isoproterenol (a non-selective beta-adrenergic receptor agonist) in phenylephrine or KCl precontracted aortic rings from 3 week and 3 month old male Wistar rats. Both the mechanism and the subtype of beta-adrenergic receptor underlying the response to isoproterenol in the both age groups were examined. Endothelial removal, pre-contraction with KCl (40 mM), pre-treatment with tetraethylammonium or with N(omega)-Nitro-L-arginine methyl ester inhibited the vasodilator response to isoproterenol only in aortic rings from older rats. The inhibition was total when TEA and L-NAME were administered together. In both age groups the response to isoproterenol was unaffected by the beta1-adrenergic antagonist CGP20712A, but was significantly inhibited by ICI 118551 (a beta2-adrenergic-antagonist) and to a greater extent by SR 59230A (a non-selective beta 3-adrenergic antagonist), the inhibition being more evident in the older rats. Unlike younger rats, in older animals the response to isoproterenol was partially dependent on endothelial nitric oxide and on K+ channels. In both age groups, beta2- and beta3-, but not beta1-adrenergic receptors were involved. The degree of relative participation of beta2 and beta3 adrenergic receptors may change with age and explain the differences in response to isoproterenol.
authors: Seccion de Estudios de Posgrado e Investigación de la Escuela Superior de Medicina, I.P.N, México. drcarloscastillo@hotmail.com
authors: Maria del Carmen
authors: Mdel C
authors: Castillo-Hernandez
authors: Noemi
authors: N
authors: Meraz-Cruz
authors: Gustavo
authors: G
authors: Guevara-Balcazar
authors: Jorge
authors: J
authors: Lopez-Canales
authors: Oscar
authors: O
authors: Lopez-Canales
authors: Norma
authors: N
authors: Galindo
authors: Carlos
authors: C
authors: Castillo-Henkel
mesh_terms: D000367:Age Factors; D000818:Animals; D001011:Aorta / Q000187:drug effects* / Q000502:physiology; D066298:In Vitro Techniques; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D011189:Potassium Chloride / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D011943:Receptors, Adrenergic, beta / Q000502:physiology*; D013757:Tetraethylammonium Compounds / Q000494:pharmacology; D014664:Vasodilation / Q000187:drug effects*
chemical_list: D011943:Receptors, Adrenergic, beta; D013757:Tetraethylammonium Compounds; D011189:Potassium Chloride; D007545:Isoproterenol; D019331:NG-Nitroarginine Methyl Ester