The effect of adenosine triphosphate, magnesium chloride and phospholipids on crystal formation in the demineralized shell-repair membrane of the snail, Helix pomatia L. An in vitro study.

The effect of adenosine triphosphate (ATP), magnesium chloride (MgCl2) and phospholipids on the calcium-binding activity and crystal formation within the decalcified shell-repair membrane of the snail, Helix pomatia, was studied in vitro. The application of ATP produced a characteristic dual effect on calcification: (1) It strongly inhibited the formation of inorganic calcium carbonate (CaCO3) crystals. (2) It stimulated the development of organic crystalline bodies and induced deposition of amorphous calcium carbonate. The demineralized shell-repair membranes became white and rigid after incubation for 7 days in the medium containing 1.0 mM ATP. The inhibitory effect of Mg2+ on CaCO3 crystal formation was diminished by reduction of the concentration of MgCl2 in the incubation solution. Thus, after incubation for only 24h, 1.0 mM MgCl2 promoted the formation of birefringent CaCO3 crystals within the repair membranes. The principal effect of phospholipids on the demineralized shell-repair membrane was stimulatory, but after application of phospholipids to the medium, the formation of crystals proceeded slowly. The very large, composite crystals that were formed within the repair membranes showed strong birefringence. In all cases the development of the crystals and the organic crystalline bodies occurred in close vicinity to the amoebocytes. The role of ATP, MgCl2 and phospholipids in the recalcification of shell-repair membrane is discussed.