The "Mid-2009" and "Mid-2010" MacBook Pro models support 1066 MHz PC3-8500 DDR3 SO-DIMMs and officially and unofficially support a maximum of 8 GB of RAM with one odd exception.
Specifically, as discovered by OWC, the 13-Inch "Mid-2010" MacBook Pro models (and only the 13-Inch models) -- the MacBook Pro "Core 2 Duo" 2.4 13" Mid-2010 and "Core 2 Duo" 2.66 13" Mid-2010 identified by MacBookPro7,1 -- can support up to 16 GB of RAM with dual 8 GB memory modules if they are running OS X 10.7.5 or higher, have been updated to use the latest EFI, and are equipped with proper specification memory modules. If running a version of Mac OS X 10.6 "Snow Leopard," these models only can use 8 GB of RAM.