The effects of pentoxifylline on the plasma membrane Ca2+ ATPase in age-separated rat and human erythrocytes.

Pentoxifylline, a dimethyl xanthine derivative given to patients with peripheral vascular disorders, increases erythrocyte deformability, diminishes Ca2+ entry, inhibits Ca(2+)-dependent transglutaminase activity and elevates ATP levels. The present study examined the effects of pentoxifylline on the Ca2+ pump ATPase, an enzyme which regulates intracellular Ca2+ levels. Studies were carried out with inside-out vesicles (IOVs) prepared from young (Ey) and old (Eo) human and rat erythrocytes.

A p-nitrophenylphosphatase activity associated with the human erythrocyte membrane.

A p-nitrophenylphosphatase activity has been identified as a component of the human erythrocyte membrane. This activity is distinct from that associated with the cell's Na(+)+K(+)-dependent ATPase, Ca(2+)-dependent ATPase, or spectrin phosphatase. The activity described here is stimulated by Mn2+ but not by Ca2+ with or without calmodulin.

A 20 kDa erythrocyte membrane phosphoprotein.

A small (approximately 20 kDa) protein associated with the human erythrocyte membrane undergoes phosphorylation that is potentiated by the addition of phosphatidylinositol. It is indicated that phosphatidylinositol 4.5-bisphosphate, generated in situ during the protein phosphorylation reaction.

Ca2+ transport activities of inside-out vesicles prepared from density-separated erythrocytes from rat and human.

The plasma membrane Ca2+ ATPase in erythrocytes is vital for the maintenance of intracellular Ca2+ levels. Since the cytoplasmic Ca2+ concentration is elevated in older erythrocytes, the properties of the Ca2+ transport ATPase were examined during cell aging using inside-out vesicles (IOVs) prepared from density-separated, young (less dense, Ey) and old (more dense, Eo) rat and human erythrocytes. The transport of Ca2+ and the coupled hydrolysis of ATP were measured using radiolabeled substrates.

Prevention by pentoxifylline of transient Ca2+ accumulation and transglutaminase activation in rat erythrocytes.

The authors have examined the effects of pentoxifylline, a drug used to improve peripheral blood flow in patients with vascular disorders, on shear-induced periodic Ca2+ entry and its consequences in the rat erythrocyte. To study the effects of periodic Ca2+ entry on Ca2+ dependent processes, erythrocytes, with and without pentoxifylline, were subjected to rotational shear produced by swirling-cell suspensions in an isosmotic medium for 5-second intervals. Pulses of increasing duration from 5-30 seconds promoted increased accumulation of 45Ca2+; intermittent 5 sec pulses, at 10-minute intervals, produced a stepwise accumulation of 45Ca2+.