Steroidogenic and pressor activity of angiotensin analogues in the rat.

1. A classical 6 point assay in vitro for measuring aldosterone stimulating activity has been developed. 2. The steroidogenic potency of Ile5-angiotensin II was 62% of that given by Val5-angiotensin II. Ile5-angiotensin III (Des-Asp1-Ile5-angiotensin II) was likewise 50% as active as Val5-angiotensin III (Des-Asp1-Val5-angiotensin II). Similar results were obtained in the pressor and myotropic assays. 3. Ile5-angiotensin III and Val5-angiotensin III had only 7% and 16% respectively of the steroidogenic activity of Val5-angiotensin II. 4. Sar1-Ile5-angiotensin II was 2.3 times as potent as Val5-angiotensin II in aldosterone-stimulating activity. The corresponding activities of Me2-Gly1-angiotensin II, Pro1-angiotensin II and Pro31-angiotensin II were 71%, 15% and 3% of Val5-angiotensin II respectively.