Angiotensin tachyphylaxis in normal and everted rings of rabbit aorta

The development of tachyphylaxis to angiotensin II and to [1-sarcosine]angiotensin II ([Sar1]angiotensin II) was studied in rabbit aorta helical strips, normal rings and everted rings, with and without a functional endothelium. Normal rings developed tachyphylaxis to both angiotensin II and [Sar1]angiotensin II, helical strips only to [Sar1]angiotensin II and everted rings did not show tachyphylaxis. The presence or absence of a functional endothelium had no effect on the development of tachyphylaxis in any of the preparations. Measurement of the intraluminal pH of the normal rings with an antimony minielectrode showed that under steady state conditions there was a pH gradient between the intima side of the vessel wall and the outside bath medium. This could be responsible for the greater susceptibility of the normal rings to tachyphylaxis.