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Peptidases and smooth muscle cell angiotensin II receptor pharmacology
R B Cohen1, M L Webb, K E Dickinson
1Department of Cardiovascular Biochemistry, Bristol-Myers Squibb Pharmaceutical Research Institute, Princeton, NJ 08643-4000.
Abstract:
Angiotensin (A) II receptors on rat aortic smooth muscle (RASM) cell membranes were characterized using the radioligand [125I][Sar1Ile8]AII ([125I]SI-AII). Angiotensin I, AII, and AIII inhibited specific [125I]SI-AII binding, and their rank order of potencies, and Ki values (nM) were: AII (3.7) > AI (32.5) > or = AIII (54.0), which differed from that observed for rat adrenal cortex: AII (0.85) > AIII (3.3) >> AI (100). Similar results were observed for RASM membranes in the presence of guanine nucleotides, and for intact cells in the absence or presence of an internalization inhibitor. Lowering the incubation temperature from 37 degrees C to 4 degrees C, or inclusion of PMSF (1 mM), and preparing membranes in the presence of EGTA (1 mM) altered the rank order of potencies and Ki values (nM) of the angiotensin peptides to: AII (1.1) > AIII (7.0) >> AI (144). [125I]Angiotensin I was metabolized completely over the course of 90 min to small (