Different role of endothelin ETA and ETB receptors and endothelial modulators in diabetes-induced hyperreactivity of the rabbit carotid artery to endothelin-1.

The influence of diabetes on regulatory mechanisms and specific receptors implicated in the contractile response of isolated rabbit carotid arteries to endothelin-1 was examined. Endothelin-1 induced a concentration-dependent contraction that was greater in arteries from diabetic rabbits than in arteries from control rabbits. Endothelium removal or N(G)-nitro-L-arginine enhanced contractions in response to endothelin-1 only in control arteries, without modifying the endothelin-1 response in diabetic arteries. Indomethacin, furegrelate (thromboxane A(2) inhibitor), or cyclo-(D-Asp-Pro-D-Val-Leu-D-Trp) (BQ-123; endothelin ET(A) receptor antagonist) inhibited the contractions in response to endothelin-1, the inhibition being greater in diabetic arteries than in control arteries. 2,6-Dimethylpiperidinecarbonyl-gamma-methyl-Leu-N(in)-(methoxycarbonyl)-D-Trp-D-Nle (BQ-788; endothelin ET(B) receptor antagonist) enhanced the contraction elicited by endothelin-1 in control arteries and displaced to the right the contractile curve for endothelin-1 in diabetic arteries. In summary, diabetes induces hyperreactivity of the rabbit carotid artery to endothelin-1 by a mechanism that at least includes: (1) enhanced activity of muscular endothelin ET(A) receptors; (2) impairment of endothelin ET(B) receptor-mediated nitric oxide (NO) release; and (3) enhancement of the production of thromboxane A(2).