Role of the PKC/CPI-17 pathway in enhanced contractile responses of mesenteric arteries from diabetic rats to alpha-adrenoceptor stimulation.
Protein kinase C (PKC) may contribute to enhanced contractile responses of arteries from streptozotocin-diabetic rats to stimulation of G-protein coupled receptors. This was investigated by comparing the effects of PKC inhibitors on contractile responses of mesenteric arteries from diabetic and age-matched control rats to noradrenaline (NA) and endothelin-1 (ET-1). The effects of NA and ET-1 on the distribution of three isoforms of PKC implicated in contraction were also determined. In addition, the effect of NA on phosphorylation of CPI-17, a substrate for PKC, was investigated. Contractile responses of endothelium-denuded arteries from diabetic rats to NA were enhanced, but were normalized by PKC inhibition. In contrast, contractile responses to ET-1 were not significantly different, and were blocked to a similar extent by PKC inhibition, in arteries from control and diabetic rats.NA produced only a small increase in particulate levels of PKCepsilon in control arteries (to 125+/-8% of levels in untreated arteries), but a significant increase in particulate PKCalpha (to 190+/-22%) and a much greater increase in particulate PKCepsilon (to 230+/-19%) in arteries from diabetic rats. ET-1 increased particulate PKCalpha and epsilon to a similar extent in arteries from control and diabetic rats.NA significantly enhanced CPI-17 phosphorylation from a basal level of 22+/-10 to 71+/-7% of total in arteries from diabetic rats, and this was prevented by PKC inhibition. NA had no detectable effect on CPI-17 phosphorylation in arteries from control rats. These data suggest that NA-induced activation of PKC and CPI-17, its downstream target, is selectively enhanced in arteries from diabetic rats, and mediates the enhanced contractile responses to this agonist.
Mueed
Irem
I
Division of Pharmacology and Toxicology, Faculty of Pharmaceutical Sciences, University of British Columbia, 2146 East Mall, Vancouver, BC, Canada V6T 1Z3.
Zhang
Lili
L
MacLeod
Kathleen M
KM
D000818:Animals; D003921:Diabetes Mellitus, Experimental / Q000201:enzymology / Q000503:physiopathology*; D019332:Endothelin-1 / Q000494:pharmacology; D007527:Isoenzymes / Q000032:analysis / Q000502:physiology; D008297:Male; D008638:Mesenteric Arteries / Q000201:enzymology / Q000502:physiology*; D009124:Muscle Proteins / Q000502:physiology*; D009638:Norepinephrine / Q000494:pharmacology; D010750:Phosphoproteins / Q000502:physiology*; D010766:Phosphorylation; D011493:Protein Kinase C / Q000032:analysis / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D011942:Receptors, Adrenergic, alpha / Q000502:physiology*; D043562:Receptors, G-Protein-Coupled / Q000502:physiology; D014661:Vasoconstriction / Q000187:drug effects
D019332:Endothelin-1; D007527:Isoenzymes; D009124:Muscle Proteins; D010750:Phosphoproteins; C491519:Ppp1r14a protein, rat; D011942:Receptors, Adrenergic, alpha; D043562:Receptors, G-Protein-Coupled; D011493:Protein Kinase C; D009638:Norepinephrine