Why aren't ROS environment variables updated

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I have to install the ROS from source.

So I followed this link http://wiki.ros.org/kinetic/Installat... and finished installing the ROS Base here: /home/me/ros_base

Then I downloaded some other packages, put them into /home/me/ros_base/src and executes the commands as below:

cd /home/me/ros_base
rosdep install --from-paths src --ignore-src --rosdistro kinetic -y
./src/catkin/bin/catkin_make_isolated --install -DCMAKE_BUILD_TYPE=Release

However, I check the ROS environment variables with the command printenv | grep ROS and I get such an output:

ROS_ROOT=/home/me/ros_base/install_ioslated/share/ros
ROS_MASTER_URI=http://localhost:11311

I'm sure that I've execute source /home/me/ros_base/install_isolated/setup.bash and source /home/me/ros_base/devel_isolated/setup.bash.

But why haven't the variable ROS_PACKAGE_PATH been set?