title: Calcium ion-dependent diacylglycerol accumulation in erythrocytes is associated with microvesiculation but not with efflux of potassium ions.
abstract: Erythrocytes from several different species were exposed to Ca2+ and the bivalent-cation ionophore A23187. The lipid composition, morphology and K+ permeability of the treated cells were investigated. Erythrocytes from human, rat, guinea pig and rabbit (a) showed an increased concentration of 1,2-diacyl-sn-glycerol and enhanced labelling of phosphatidate with 32P, (b) underwent echinocytosis and outward vesiculation, and (c) rapidly released much of their intracellular K+. Pig cells showed only the K+ loss, and ox and sheep (high-K+) cells showed none of these Ca2+-evoked effects. All of the cells underwent stomatocytosis and inward vesiculation when treated externally with Clostridium perfringens phospholipase C. These results support the idea that there is a correlation between the asymmetric insertion of diacylglycerol (or ceramide) into the membrane and the shape-changes leading to microvesiculation, but they indicate that Ca2+-triggered K+ efflux and diacylglycerol production are unrelated events. Erythrocytes of chicken and turkey showed no Ca2+-stimulated K+ efflux. They showed slight ionophore A23187-stimulated vesiculation, but this appeared to be associated with the appearance in the membrane of ceramide rather than of diacylglycerol. Phospholipase C treatment caused very similar changes in morphology and phosphatidate labelling to those seen in mammalian erythrocytes.
mesh_terms: D000818:Animals; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002417:Cattle; D002645:Chickens; D004075:Diglycerides / Q000097:blood*; D004912:Erythrocytes / Q000378:metabolism*; D005989:Glycerides / Q000097:blood*; D006168:Guinea Pigs; D006801:Humans; D010740:Phospholipases / Q000378:metabolism; D011188:Potassium / Q000378:metabolism*; D011817:Rabbits; D051381:Rats; D012756:Sheep; D013552:Swine; D014422:Turkeys
chemical_list: D004075:Diglycerides; D005989:Glycerides; D000001:Calcimycin; D010740:Phospholipases; D011188:Potassium; D002118:Calcium