Don't need no steenkin' loops! This is MATLAB!!! :)
Above uses the fact that most ML functions in general and kurtosis in particular are written to operate on matrices by column; hence the ".'" to transpose your row-oriented array to columns first, then to transform the result back to a column to match rows.
mean, std and friends all operate same way.
NB: all of these also have an optional DIM argument that can be used to avoid the explicit transpose by saying which dimension of the array to operate over. In this case you want to operate on rows which is second dimension so
NB2: the  placeholder, the DIM argument is the third, the second optional argument is a flag for bias correction (default is on). See
for details of this.
BTW, the answer to the original question because every once in a while it is necessary to loop over an array, would be something like
Obviously, the function called can be any that accepts a vector, not just kurtosis, I just used for simplicity to illustrate the calling syntax.