gms | German Medical Science

Endothelins exert their biological effects via two subtypes of G protein-coupled receptors, termed ETA and ETB. In the vasculature, ETA is constitutively expressed on vascular smooth muscle cells (VSMC) where it mediates potent vasoconstricting and mitogenic effects.

To investigate the biological role of ETA and its possible interactions with other vasoactive systems in VSMC in vivo, we established a transgenic rat model overexpressing the human ETA receptor under control of the murine SM22alpha promoter.

Microinjection of the purified construct into fertilized Sprague-Dawley rat oocytes was carried out according to standard procedures and screening of transgene positives was performed by genomic PCR. 5 animals positive for SM22-ETA were identified and breeded to establish transgenic lines. Transgene expression was analyzed by RT-PCR.

Vascular function was analyzed in one transgenic line (L6351) using a pressure myograph which showed attenuated contraction to supraphysiological potassium concentrations and a significantly decreased responsiveness to the alpha-adrenergic stimulus phenylephrine as compared to non-transgenic controls. In contrast, no alterations in the contractile response were observed when angiotensin II or the thromboxane A2 agonist, U 46619, were applied.

Using a transgenic model, we have revealed a specific in vivo interaction of ETA and alpha-adrenergic receptors which is of putative significance for bloood pressure control.