You may remember Brucie from Grand Theft Auto IV -- he was a motorhead in that game and a source for among other things some of the most amusing dialogue there.
He is one of the few Characters who has emigrated to San Andreas and his call to you is to let you know (and unlock) about his delivery service which specializes in Bull Shark Testosterone -- which is a performance enhancing substance that can help you out in battle!
To obtain this simply ring him up for a delivery before you enter a battle and you get the benefits of his um, science... Just saying.
Where do i find bull shark testosterone after i pay $500 for it?