Demonstration of both beta 1- and beta 2-adrenoceptors mediating negative chronotropic effects on spontaneous activity in isolated bovine mesenteric lymphatics.
The pharmacological classification of beta-adrenoceptor subtypes in isolated bovine mesenteric lymphatics was studied by using various beta-adrenoceptor agonists and antagonists. Isoproterenol (ISP) (10(-10)-10(-8) M) produced dose-dependent negative chronotropic effects on the rhythm of spontaneous contractions in the lymphatic preparation. The ISP-induced effects were dose-dependently blocked by pretreatment with 10(-8)-10(-7) M metoprolol (a selective beta 1 antagonist) as well as 10(-8)-10(-7) M propranolol (a beta 1 and beta 2 antagonist). Dobutamine (a selective beta 1 agonist) caused a dose-dependent negative chronotropic effect, which was significantly blocked by pretreatment with 10(-8) M metoprolol. Salbutamol and procaterol (selective beta 2 agonists) also produced dose-dependent negative chronotropic effects, which were dose-dependently inhibited by pretreatment with 10(-8)-10(-7) M propranolol, but not by 10(-7) M metoprolol. The decreasing order of the relative potency was as follows: ISP greater than procaterol greater than salbutamol greater than dobutamine. These results suggest that bovine mesenteric lymphatics contain both beta 1- and beta 2-adrenoceptors and that both subtypes can produce a negative chronotropic effect on the rhythm of spontaneous contractions, when stimulated.
Watanabe
N
N
First Department of Physiology, Shinshu University School of Medicine, Matsumoto, Japan.
Kawai
Y
Y
Ohhashi
T
T
D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D000319:Adrenergic beta-Antagonists / Q000494:pharmacology; D000818:Animals; D002417:Cattle; D003864:Depression, Chemical; D066298:In Vitro Techniques; D008208:Lymphatic System / Q000187:drug effects / Q000502:physiology*; D008643:Mesentery; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology; D011943:Receptors, Adrenergic, beta / Q000145:classification / Q000187:drug effects / Q000502:physiology*
D000318:Adrenergic beta-Agonists; D000319:Adrenergic beta-Antagonists; D011943:Receptors, Adrenergic, beta