Activity profiles of dalargin and its analogues in mu-, delta- and kappa-opioid receptor selective bioassays.

1. To elucidate the structural features ensuring action of [D-Ala2, Leu5]-enkephalyl-Arg (dalargin), a series of dalargin analogues were tested for their effectiveness in depressing electrically-evoked contractions of the guinea-pig myenteric plexus-longitudinal muscle preparations (mu- and kappa-opioid receptors) and the vasa deferentia of the hamster (delta-opioid receptors), mouse (mu-, delta- and kappa-opioid receptors), rat (similar to mu-opioid receptors) and rabbit (kappa-opioid receptors). The naloxone KB values in the myenteric plexus were also obtained. 2. [L-Ala2]-dalargin was 19 times less potent than dalargin, and its pharmacological activity was peptidase-sensitive. The ratio of delta-activity to mu-activity for [L-Ala2]-dalargin was 6.78, and KB was 7.9 nM. This emphasizes the role that D-configuration of Ala2 plays in determining the active folding of dalargin molecule as well as in conferring resistance to peptidases. 3. [Met5]-dalargin was equipotent to dalargin in the myenteric plexus, but was more potent in the vasa deferentia of hamster and mouse (KB=5.5 nM). Leu5 and the interdependence of Leu5 and D-Ala2 are of importance for the selectivity of dalargin for mu-opioid receptors. 4. Dalarginamide was more potent and selective for mu-opioid receptors than dalargin, whilst dalarginethylamide, though equipotent to dalarginamide in the myenteric plexus, was more potent at delta-opioid receptors (KB=5.0 nM). [D-Phe4]-dalarginamide and N-Me-[D-Phe4]-dalarginamide were inactive indicating the contribution of L-configuration of Phe4 to the pharmacological potency of dalargin. 5. N-Me-[L-Phe4]-dalarginamide possessed the highest potency and selectivity for mu-opioid receptors (the ratio of delta-activity to mu-activity was 0.00053; KB=2.6 nM). The CONH2 terminus combined with the N-methylation of L-Phe4 increased the potency and selectivity of dalargin for mu-opioid receptors.

Semisynthetic insulin analogues modified in positions B24, B25 and B29.

New semisynthetic analogues of human insulin, modified in the C-terminal region of the B-chain, were prepared to refine our understanding of the importance of particular amino acid residues in the expression of hormone biological properties. The following insulin analogues were synthesized by trypsin-catalyzed peptide-bond formation between the C-terminal arginineB22 of des-octapeptide(B23-B30)-insulin and synthetic octapeptides with the epsilon-amino group of lysineB29 protected by a phenylacetyl group: [L-Lys(Pac)B29]insulin, [D-PheB24,B25,L-Lys(Pac)B29]insulin and [D-Phe(p-Et)B24, L-Lys(Pac)B29]insulin. Enzymatic deprotection using immobilized penicillin amidohydrolase yielded: human insulin, [D-PheB24,B25]insulin and [DPhe(p-Et)B24]-insulin. Biological in vitro potencies (specific binding to cultured human lymphocytes IM-9 and lipogenic potency in isolated rat adipocytes) of the semisynthetic analogues were estimated, ranging from 0.2 to 100% relative to porcine insulin.