The effects of diabetes on β-adrenoceptor mediated responsiveness of human and rat atria

Abstract

The literature on the influence of diabetes on cardiac β-adrenoceptors is still a matter of controversy. Hence, in the present study, the responsiveness of spontaneously beating right atria from streptozotocin (STZ)-diabetic rats to β-adrenoceptor agonists were compared with those from non-diabetic controls. The responsiveness of right atria from 8-week diabetic rats to the chronotropic effects of isoprenaline, noradrenaline and fenoterol was found to be unchanged. As the disease progressed, on the other hand, the diabetic atria were found to have decreased responsiveness to the chronotropic effects of noradrenaline. The pD 2 value and maximum chronotropic effect of noradrenaline were decreased in 14-week diabetic right atria when compared with those from age-matched controls. A significant decrease in the maximum chronotropic response to isoprenaline with no change in pD 2 value was also observed in 14-week diabetes. These results suggest that β 1- but not β 2-adrenoceptor mediated chronotropic responses were reduced in the right atria due to the increase in the duration of diabetes. On the other hand, the inotropic responses to β-adrenoceptor agonists were also assessed on diabetic and nondiabetic human atrial tissue. There were no significant differences in the inotropic responses to each agonists in either of the diabetic and nondiabetic human atrial tissues. The full agonist potency order was isoprenaline≥fenoterol>noradrenaline.