Phorbol 12,13-dibutyrate potentiates alpha 2-adrenoceptor-mediated contraction in the rat saphenous vein.

The responses of the rat saphenous vein to potassium depolarization, noradrenaline and B-HT 920 were potentiated significantly by phorbol 12,13-dibutyrate (PDBu) (10 nM). In contrast, only the contraction induced by potassium depolarization was potentiated by PDBu in the rat tail artery. The responses to noradrenaline and methoxamine were slightly inhibited. These results suggest that PDBu may have a differential effect on the responses of the two subtypes of alpha-adrenoceptors-potentiation for the alpha 2-adrenoceptors in the rat saphenous vein and inhibition for the alpha 1-adrenoceptors in the rat tail artery.