UDP-Glc-induced efflux of radiolabeled solutes
associated with Golgi vesicles. Golgi vesicles (300 μg of protein)
were incubated for 10 min with 1 μm (3 μCi/nmol)
[β-32P]UDP-Glc (A), [α-32P]UDP-Glc (B),
or [3H]UDP-Glc (C). After the incubation a pulse of cold
UDP-Glc (1 mm) was added to each sample (indicated with an
arrow), and the incubation continued for 0, 3, or 5 min. Finally, the
incubations were stopped by filtration, and the radioactivity that
remained associated with the vesicles after the pulse of UDP-Glc was
determined by liquid-scintillation counting. The amount of solutes
associated with the vesicles is expressed in equivalents of UDP-Glc at
the beginning of the incubation. The measurements were done in
triplicate and the average and its deviation are depicted in the
figure. The incorporation of the various substrates, obtained from
Figure 6, is depicted with a broken line.