Role of nitric oxide and endothelin in endothelial maintenance of vasoconstrictor responses in aortas of diabetic female rats.
BACKGROUND
Diabetes differentially affects the vascular system in males and females. Although various results have been reported, very few studies have focused on responses in females. In the present study, we investigated contractile responses to norepinephrine in aortas of alloxan-diabetic female rats and evaluated endothelial modulation of these responses.


METHODS
Concentration-response curves were constructed to norepinephrine in the absence or presence of N(G) -nitro-l-arginine methyl ester (l-NAME), indomethacin, losartan, tezosentan, and calphostin C; pre-pro-endothelin mRNA expression was evaluated; and norepinephrine-stimulated expression of phosphorylated (p-) Akt Ser(473) , p-endothelial nitric oxide synthase (eNOS) Ser(1177) , and p-eNOS Ser(633) was determined in endothelial cells incubated in the presence of low (5 mmol/L) or high (25 mmol/L) glucose concentrations.


RESULTS
Similar maximal responses (Rmax ) to norepinephrine were seen in control and diabetic endothelium-intact aortas; however, Rmax was reduced in diabetic endothelium-denuded aortas. Incubation of endothelium-intact aortas with 100 μmol/L l-NAME increased Rmax in the control group only. Inhibition of cyclo-oxygenase (10 μmol/L indomethacin) and blockade of angiotensin II receptors (10 μmol/L losartan) reduced Rmax in endothelium-intact aortas in both the control and diabetic groups. Blockade of endothelin receptors (0.1 μmol/L tezosentan) and inhibition of protein kinase C (PKC; 0.1 μmol/L calphostin C) reduced Rmax only in endothelium-intact aortas from diabetic rats. Pre-pro-endothelin mRNA expression was increased in aortas from diabetic female rats. Finally, p-Akt Ser(473) , p-eNOS Ser(1177) , and p-eNOS Ser(633) levels were enhanced after norepinephrine stimulation only in low glucose-treated endothelial cells.


CONCLUSIONS
In aortas of diabetic female rats, reductions in smooth muscle contractile responses to norepinephrine are counterbalanced by the endothelium via reduced eNOS activation and increased endothelin release and PKC activation.
Department of Pharmacology, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil.
Simone M
SM
Sartoretto
Rosângela
R
Santos-Eichler
Rita
R
de Cássia A Tostes
Maria Helena C
MH
Carvalho
Eliana H
EH
Akamine
Zuleica B
ZB
Fortes
D000818:Animals; D001013:Aorta, Thoracic / Q000378:metabolism / Q000503:physiopathology*; D003921:Diabetes Mellitus, Experimental / Q000378:metabolism / Q000503:physiopathology*; D016232:Endothelins / Q000378:metabolism*; D004730:Endothelium, Vascular / Q000378:metabolism*; D005260:Female; D009131:Muscle, Smooth, Vascular / Q000378:metabolism / Q000503:physiopathology*; D009569:Nitric Oxide / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D014661:Vasoconstriction
D016232:Endothelins; D012333:RNA, Messenger; D009569:Nitric Oxide