Effects of Polypeptide and Protein Hormones on Lipid Monolayers : I. Effect of insulin and parathyroid hormone on monomolecular films of monooctadecyl phosphate and stearic acid

Insulin in low concentrations inhibits the uptake of Ca⁺⁺ by the monooctadecyl (stearyl) phosphate monolayer (at air-water interface) and facilitates the release of Ca⁺⁺ adsorbed to the monolayer. These effects of insulin are more pronounced at higher insulin concentrations. Evidence is presented that a relatively intact insulin molecule competes with Ca⁺⁺ for the free phosphate group of the monolayer. Albumin has a slight inhibitory action on calcium uptake and parathyroid hormone has no observable action on calcium uptake or release.