Why the study?
Does prolonged infusion of dopexamine alter beta 1- and beta 2-adrenoceptor density in guinea-pig myocardium?
Does prolonged infusion of dopexamine alter beta 1- and beta 2-adrenoceptor density in guinea-pig myocardium?
Prolonged dopexamine infusion reduces beta 2-adrenoceptor density in guinea-pig myocardium, likely due to its partial agonist activity at beta 2-adrenoceptors and antagonist activity at beta 1-adrenoceptors.
Does not support clinical dopexamine dosing changes; leaves open human beta-adrenoceptor responses to prolonged infusion.
The effects of 7-day infusion of dopexamine (50 and 200 micrograms kg-1h-1) were examined on beta 1- and beta 2-adrenoceptors in guinea-pig left ventricular membranes. 2. Receptor binding performed using the high affinity radioligand (-)-[125I]-cyanopindolol (CYP) and the beta 1-adrenoceptor antagonist CGP 20712A showed that treatment with dopexamine 200 micrograms kg-1h-1 caused a 45% reduction in beta 2-adrenoceptors and a small but not significant increase in beta 1-adrenoceptors. 3. Functional effects of dopexamine were examined in the guinea-pig isolated electrically driven left atria and K(+)-depolarized uterus. Dopexamine was an antagonist at beta 1-adrenoceptors in left atria (pKB = 4.49), and a partial agonist at beta 2-adrenoceptors in the uterus (alpha = 0.78, pD2 = 6.59). 4. The effects of dopexamine on beta 1- and beta 2-adrenoceptor density in guinea-pig ventricular myocardial membranes may be related to agonist activity at beta 2-adrenoceptors and antagonist activity at beta 1-adrenoceptors.
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Williams et al. (1990) studied this question.
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