Abstract: | Methylamine influx into Hydrodictyon has been measured withl4C]methylamine. The influx increases with rising externalpH up to about pH 8. Between pH 8 and 9 influx remains quiteconstant, with a further increase above pH 9. Influx is light-dependent,temperature-sensitive, and is decreased by . During short-term influx (less than 4 h) metabolism of methylamineappears negligible. Prolonged influx results in CH3 accumulation, and efflux of K+, Na+, and H+. There is no effecton Cl influx. Methylamine decreases the membrane electricp.d. by 60120 mV at external concentrations of 0?21?0mM. The results indicate that, below pH 9, methylamine enters thecell almost entirely as CH3 . It is suggested that a passive electrogenic uniporter is involved, and thatby analogy uniport of may also be expected in Hydrodictyon. The results are discussed in relation to theevidence for uptake of CH3 and by other plant cells. |