Figure 5. PDE enzymatic activities in
isolated rod outer segment. Phosphodiesterase (PDE) activities were
measured by thin layer chromatography using [8-3H] cGMP as
the hydrolysis substrate. Rod outer segment (ROS) from dark-adapted
rats were isolated, permeabilized, mixed with either 0.5 mM GTP, 0.5 mM
GTPγS, or no nucleotide before they were exposed to light. Maximal PDE
activity in ROS was elicited by trypsin activation (p≤0.001 for all
groups).