Evaluation of Mg2+ as an intracellular regulator of uridine uptake

✍ Scribed by C. Vidair; H. Rubin

• Publisher: John Wiley and Sons
• Year: 1981
• Tongue: English
• Weight: 737 KB
• Volume: 108
• Category: Article
• ISSN: 0021-9541
• DOI: 10.1002/jcp.1041080305

✦ Synopsis

Abstract

The rate of uptake of the nucleoside uridine increases within minutes after adding a growth stimulus to quiescent 3T3 cells. We have previously shown this uptake rate to be highly sensitive to changes in the intracellular concentration of Mg^2+^. In the present paper, the alteration of uptake by Mg^2+^ is shown to occur at the phosphorylation step — the same point at which serum acts to modulate uridine uptake. The serum stimulation of uridine uptake can be mimicked by Mg^2+^ alone or blocked by partially depleting cells of their Mg^2+^. Work with cell‐free extracts shows that the uridine kinase enzyme responds to Mg^2+^ in a manner similar to that exhibited by whole cells whose concentrations of Mg^2+^ have been raised. In addition, the enzyme's inhibition by ATP is relieved by raising the Mg^2+^ concentration. Thymidine uptake, a reaction which does not respond quickly to mitogenic stimulation, is unaffected by alterations in Mg^2+^ concentration. These results are discussed in terms of a possible role for Mg^2+^ as an intracellular regulator of uridine uptake and other reactions of the coordinate response of cells to external effectors.