Further studies of the action on smooth muscle of eledoisin-fragments and eledoisin-like hepta-and hexapeptides

The effect of eledoisin fragments and eledoisin-related peptides was studied in vivo on dog, rabbit and cock blood pressure, on rabbit uterus and on guinea pig brocchospasm, and in vitro on guinea pig seminal vesicles. The following conclusions were drawn: (1) At least six amino acids are necessary for the biological activity. (2) The nona-and decapeptides are in general more active than eledoisin. (3) The substitution of some amino acids in the hepta-and hexapeptide chain can yield more specific and more active compounds. Thus the presence of lysine instead of alanine in the hexapeptide increased the affinity of the new peptides for vascular smooth muscle and the replacement of the methioninamide residue with the ethioninamide residue caused a considerable enhancement of all activity except that on the guinea pig bronchial muscles.