Is the adrenal angiotensin receptor angiotensin II--or angiotensin III like?

In order to determine whether the adrenal receptor is primarily directed at angiotensin II (AII) or angiotensin III (AIII) the following in vitro experiments were performed examining aldosterone responsiveness in isolated glomerulosa cells. 1) Cells exposed to increasing doses (2.4 X 10(-10)M - 2.4 X 10(-6)M) of AII or AIII were found to be significantly more responsive to AII (AII's ED50 was 6.3 X 10(-10) M vs AIII's 4.6 X 10(-9)M P less than 0.001). 2) Octapeptide analogues (Sar1 Ala8 and Asn1 Ala8), while demonstrating different inhibitory potencies relative to each other, were equally effective in blocking AII vs AIII stimulation. 3) The heptapeptide analogues (des1 Ala8 and des1 Ile8) however, inhibited AIII stimulation preferentially (P less than 0.01). 4) The 8 alanine octapeptide analogues were better inhibitors of both AII and AIII stimulation than the 8 alanine heptapeptide analogue. 5) HPLC analysis indicated that AII and AIII were being degraded at the same rate during the incubation procedure. These results, taken together, strongly suggest that the angiotensin adrenal receptor is an AII receptor.