In Unix FAQ (for OS X) we can read:
Bash Startup Files
When a "login shell" starts up, it reads the file
/etc/profile and then ~/.bash_profile or ~/.bash_login or
~/.profile (whichever one exists - it only reads ONE of these,
checking for them in the order mentioned).
When a "non-login shell" starts up, it reads the file /etc/bashrc and then the file ~/.bashrc.
Note that when bash is invoked with the name sh, it tries to mimic the startup sequence of the Bourne shell (sh). In particular, a non-login shell invoked as sh does not read any dot files by default. See the bash man page for details.
So if you already have ~/.bash_profile, the file ~/.profile won't be automatically read by bash, therefore you can add the following lines in your ~/.bash_profile to load it:
# Load user profile file
if [ -f ~/.profile ]; then
. ~/.profile
fi