Effect of exogenous atp on sodium transport in mammalian red cells

Abstract

The effect of exogenous adenosine triphosphate (ATP) and other nucleotides on the transport of Na in various mammalian red cells has been studied. While they have no effect on the transport of Na in human and cat red cells, in dog red cells adenosine and its mono-, di- and triphosphorylated forms were found to increase Na-influx. Of these, ATP has the most striking effect, causing a more than 8-fold increase at a concentration of 0.6 mM and exerting this effect at a dose range of 10(-5) to 10(-3) M. The effect of ATP is rapid (less than 5 minutes) and can be reversed by washing or the addition of calcium or magnesium. In contrast to the adenosine series other phosphorylated nucleotides (GTP, CTP, UDP, GDP and cAMP) have no effect. The well known volume dependent Na-transport in these cells is reversed in the presence of 0.6 mM ATP. It is suggested that ATP acts on passive cation movements either by chelation of membrane charge or by a direct interaction with membrane proteins and may be involved in the volume regulation of cation transport in the dog erythrocyte.

Tetrodotoxin-sensitive Na + channels and muscarinic and purinergic receptors identified in human erythroid progenitor cells and red blood cell ghosts

“…1, but this was not always the case. Even so, the TTX-sensitive efflux was still apparent in other experiments of a similar type after correction for 22 Na that was released from the cells by hemolysis.…”

“…Fresh normal heparinized blood was centrifuged, and the red cells, after washing four times with Ϸ10 vol of an isotonic solution containing 150 mM NaCl, 20 mM Hepes, 3 mM adenosine, and 5 mM glucose at pH 7.4, were incubated in this solution for Ϸ3 h at 37°C after the addition of 200 Ci (1 Ci ϭ 37 GBq) of 22 Na and chloramphenicol. The suspension was then centrifuged, and the cells were washed four times with a solution containing 145 mM NaCl, 5 mM KCl, and 20 mM Hepes, to remove extracellular 22 Na. The 22 Na-loaded cells were then suspended (Ϸ2% hematocrit) at 4°C in this solution in the presence and absence of 2.5 mM CaCl 2 and 10 mM NaF and in the presence and absence of 3.3 M TTX.…”

“…The 22 Na-loaded cells were then suspended (Ϸ2% hematocrit) at 4°C in this solution in the presence and absence of 2.5 mM CaCl 2 and 10 mM NaF and in the presence and absence of 3.3 M TTX. The flasks were then placed at 37°C, and, after a 3-min equilibration, samples were withdrawn at the indicated times and centrifuged, and the supernatants were counted for 22 Na. All conditions were performed in duplicate whose variation was Ͻ5%.…”

“…All conditions were performed in duplicate whose variation was Ͻ5%. Calculation of the percent 22 Na released, outward rate constants, and Na ϩ efflux was the same as described (32). TTX was purchased from Calbiochem and 22 Na from PerkinElmer, and all other chemicals, wherever possible, were of reagent grade.…”

“…Furthermore, because the muscarinic agonist carbamylcholine (CCh) has been reported to induce a TTX-sensitive Na ϩ uptake in human red blood cells (19), we analyzed our preparations for messages associated with these types of membrane receptors as well. And lastly, because human (20)(21)(22) and dog (22,23) red blood cells are known to respond to extracellularly applied nucleotides, e.g., ATP, we also surveyed our preparations of human erythroid progenitor cells for transcripts identifying various types of purinergic receptors that might be present (24-27, ʈ).…”