1. 1. Like insulin, some analogues of insulin inhibited the adsorption of Ca2+ at a monooctadecyl phosphate monolayer; the inhibition was, in all cases, less than the inhibition by intact insulin. 2. 2. Facilitation of release of Ca2+ from the monolayer by insulin required that the insulin molecule be intact, as release was facilitated only very slightly when des-A1-glycine-des-B1-phenylalanine1-insulin or insulin B-chain-S-sulfonate replaced insulin, and did not occur at all in the absence of alanine in position B30. 3. 3. Vasopressin and oxytocin inhibited Ca2+ adsorption. In addition, vasopressin facilitated Ca2+ release. 4. 4. Thyrocalcitonin profoundly inhibited Ca2+ adsorption but facilitated only slightly its release. 5. 5. 3′,5′-cyclic AMP facilitated slightly the adsorption of Ca2+. 6. 6. It is suggested that the biphasic action of insulin and vasopressin on Ca2+ uptake depends upon the concurrence of a 6-membered disulfide ring at or near the N-terminus of the molecule, and a proline followed by a positively charged amino acid (arginine or lysine) in the two positions preceding the C-terminal amino acid.
ASJC Scopus subject areas
- Cell Biology