Despite the intensive study of endothelin (ET) in mammals, the primary structure and biological activity of the peptide is not known for any species of non-mammalian tetrapod. Extracts of the stomach and the liver of the European green frog Rana ridibunda contained ET-like immunoreactivity measured by RIA using an antiserum raised against human ET-1. The amino acid sequence of the peptide that was isolated in pure form from the stomach extract was identical to that of human ET-1 and the peptide purified from the liver extract was identical to human ET-3 except for a single amino acid substitution (Phe4→Tyr). These observations demonstrate that the amino acid sequences of ET family peptides have been very strongly conserved during evolution of tetrapods and suggest that the pathway of post-translational processing of preproendothelin in the frog is similar to that in mammals. Both frog/human ET-1, frog ET-3 and human ET-3 produced a concentration- dependent increase in the production of corticosteroids from perifused slices of the frog interrenal gland. The maximum responses produced by the peptides (approximately 2-fold increase over basal levels for both corticosterone and aldosterone production) were not significantly different. The potency of ET-1 (-log EC50=9.81 ± 0.01 (S.E.M.) for corticosterone and 9.52 ± 0.29 for aldosterone production) was significantly (P<0.01) greater than that of frog ET-3 (-log EC50=8.13 ± 1.6 for corticosterone and 8.15 ± 0.33 for aldosterone production) but the potencies of frog ET-3 and human ET-3 (-log EC50=8.29 ± 0.34 and 7.87 ± 0.18) were not significantly different.
ASJC Scopus subject areas
- Molecular Biology