Conformational Prerequisites for the in vitro Inhibition of Cholate Uptake in Hepatocytes by Cyclic Analogues of Antamanide and Somatostatin

Constitution and conformation determine the biological activity of a peptide, as demonstrated by comparative investigations of the inhibition of cholate uptake in liver cells by somatostatin, antamanide, cyclolinopeptide A and 1 and 2. The crystal structure of 1 is the same as that of 2 over a wide range and both react strongly cytoprotectively.