Creatine Transport in Cultured Cells of Rat and Mouse Brain

Abstract

Astroglia‐rich cultures derived from brains of newborn rats or mice use a transport system for the uptake of creatine. The uptake system is saturable, Na⁺‐dependent, and highly specific for creatine and Na⁺. Kinetic studies on rat cells revealed a K_m value for creatine of 45 μM, a V_max of 17 nmol X h⁻¹ X (mg of protein)⁻¹, and a K_m value of 55 mM for Na⁺. The carrier is competitively inhibited by guanidinopropionate (K_i= 15 μM). No such transport system was found in neuron‐rich primary cultures from embryonic rat brain. It is hypothesized that creatine transport is an astroglial rather than a neuronal function.