Protein kinase C delta contributes to increase in EP3 agonist-induced contraction in mesenteric arteries from type 2 diabetic Goto-Kakizaki rats

Prostaglandin E₂ (PGE₂), an important and ubiquitously present vasoactive eicosanoid, may either constrict or dilate systemic vascular beds. However, little is known about the vascular contractile responsiveness to and signaling pathways for PGE₂ at the chronic stage of type 2 diabetes. We hypothesized that PGE₂-induced arterial contraction is augmented in type 2 diabetic Goto-Kakizaki (GK) rats via the protein kinase Cδ (PKCδ) pathway. Here, we investigated the vasoconstrictor effects of PGE₂ and of sulprostone (EP1-/EP3-receptor agonist) in rings cut from superior mesenteric arteries isolated from GK rats (37–44 weeks old). In arteries from GK rats (vs. those from age-matched Wistar rats), examined in the presence of a nitric oxide synthase inhibitor: 1) the PGE₂- and sulprostone-induced vasocontractions (which were not blocked by the selective EP1 receptor antagonist sc19220) were enhanced, and these enhancements were suppressed by rottlerin (selective PKCδ inhibitor) but not by Gö6976 (selective PKCα/β inhibitor); 2) the sulprostone-stimulated phosphorylation of PKCδ (at Thr⁵⁰⁵), which yields an active form, was increased and 3) sulprostone-stimulated caldesmon phosphorylations, which are related to isometric force generation in smooth muscle, were increased. The protein expression of EP3 receptor in superior mesenteric arteries was similar between the two groups of rats. Our data suggest that the diabetes-related enhancement of EP3 receptor-mediated vasocontraction results from activation of the PKCδ pathway. Alterations in EP3 receptor-mediated vasocontraction may be important factors in the pathophysiological influences over arterial tone that are present in diabetic states.