How come my heat protection spray makes my hair feel so brittle?

I ALWAYS use heat protection spray when I straighten my hair, but whenever I use it, it makes the ends of my hair feel brittle! Without it, my ends are smooth and not dry at all. I'm concerned about this because I don't want any breakage to occur with my hair. I use Marc Anthony smooth and straight heat protection. Perhaps this isn't the best brand? Any suggestions?