Article date: May 1985
By: E. Malta, M. Aqleem Mian, C. Raper in Volume 85, Issue 1, pages 179-187
The effect of xamoterol and (‐)‐isoprenaline have been compared for their activity at β‐adrenoceptor sites in a number of in vitro cardiac and smooth muscle preparations.
Xamoterol produced weak positive chronotropic effects in guinea‐pig, rat and cat atria (intrinsic activity < 0.55, (‐)‐isoprenaline = 1). Positive inotropic effects were obtained in driven left atria of the cat but were absent in guinea‐pig left atrial and right ventricular strip preparations. Agonistic effects were due to β1‐adrenoceptor stimulation.
Xamoterol was without β‐adrenoceptor‐mediated inhibitory effects in guinea‐pig ileal, tracheal and uterine preparations and in the rat vas deferens and oestrogen‐primed uterus. Weak β2‐adrenoceptor‐mediated relaxation was obtained in progesterone‐primed rat uteri.
Xamoterol produced non‐specific inhibitory effects in guinea‐pig ileal and tracheal preparations.
Xamoterol acted as a competitive antagonist at βr (pA2 range = 7.4 to 7.8) and β2‐adrenoceptors (pA2 range 5.2 to 6.2) and displaced [125I]‐iodocyanopindolol from guinea‐pig left atrial (pKD = 7.25) and uterine (pKD 5.24) membrane preparations.
It is concluded that xamoterol displays a selective affinity for β1‐adrenoceptors. Although its partial agonistic actions are more evident at β1‐adrenoceptor sites, like prenalterol, xamoterol displays a degree of tissue rather than receptor‐dependent selectivity.
The effect of xamoterol and (‐)‐isoprenaline have been compared for their activity at β‐adrenoceptor sites in a number of in vitro cardiac and smooth muscle preparations.
Xamoterol produced weak positive chronotropic effects in guinea‐pig, rat and cat atria (intrinsic activity < 0.55, (‐)‐isoprenaline = 1). Positive inotropic effects were obtained in driven left atria of the cat but were absent in guinea‐pig left atrial and right ventricular strip preparations. Agonistic effects were due to β1‐adrenoceptor stimulation.
Xamoterol was without β‐adrenoceptor‐mediated inhibitory effects in guinea‐pig ileal, tracheal and uterine preparations and in the rat vas deferens and oestrogen‐primed uterus. Weak β2‐adrenoceptor‐mediated relaxation was obtained in progesterone‐primed rat uteri.
Xamoterol produced non‐specific inhibitory effects in guinea‐pig ileal and tracheal preparations.
Xamoterol acted as a competitive antagonist at βr (pA2 range = 7.4 to 7.8) and β2‐adrenoceptors (pA2 range 5.2 to 6.2) and displaced [125I]‐iodocyanopindolol from guinea‐pig left atrial (pKD = 7.25) and uterine (pKD 5.24) membrane preparations.
It is concluded that xamoterol displays a selective affinity for β1‐adrenoceptors. Although its partial agonistic actions are more evident at β1‐adrenoceptor sites, like prenalterol, xamoterol displays a degree of tissue rather than receptor‐dependent selectivity.
DOI: 10.1111/j.1476-5381.1985.tb08845.x
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