High-affinity uptake of spermine by slices of rat cerebral cortex.
The accumulation of the polyamine spermine into 0.1-mm prisms of rat cerebral cortex has been investigated at both 37 percent C and at 4 percent C. Kinetic analysis of the temperature-sensitive portion of uptake indicates two high-affinity saturable components together with an unsaturable component at high concentrations. The "very high'-affinity saturable system (K(m)= 3.8 nM) was temperature- and sodium-dependent, and significantly reduced by metabolic inhibitors, finding that are consistent with an active transport system for spermine into brain tissue. The "high'-affinity saturable component (K(m)= 0.44 micron) was sodium-dependent and inhibited by ouabain, but only partially susceptible to inhibition by 2,4-dinitrophenol and sodium cyanide. The significance of these results with respect to the function of spermine in the central nervous system is discussed.