help with a regression

Hello, I have a data frame with the following variables:
 ID, X1,X2,X3,X4,X5,Y1,Y2,Y3,Y4,Y5 and some other that do not matter, some of the X and Y can be missing (NA). I want to compute the slope of the linear regression Y ~ X for each subject, so using
 apply(DF,1,FUN,ra.rm=TRUE) now How do I define FUN? The X are different for each subject.
Thanks for any help

R.Heberto Ghezzo Ph.D.
Montreal - Canada