Attenuated contractile response of diabetic rat aorta to caffeine but not to noradrenaline in Ca(2+)-free medium.

The phasic contractions induced by noradrenaline and caffeine were compared in aortic rings from rats with 8-12 week streptozotocin-induced diabetes and age-matched control rats. In Ca(2+)-free medium, no difference was found in the magnitude of the contractile responses to 10 microM noradrenaline between control and diabetic aortas. The transient contraction induced by 20 mM caffeine was significantly diminished in diabetic aorta compared aorta. The results suggest that the ability of caffeine, but not of inositol 1,4,5-trisphosphate, to mobilize Ca2+ from intracellular stores is impaired in diabetic rat aorta.