Setting Font options in heatmap.2

This is the code inside heatmap.2 that creates the (main) axis annotation:

axis(1, 1:nc, labels = labCol, las = 2, line = -0.5, tick = 0, 
    cex.axis = cexCol)
if (!is.null(xlab)) 
    mtext(xlab, side = 1, line = margins[1] - 1.25)
axis(4, iy, labels = labRow, las = 2, line = -0.5, tick = 0, 
    cex.axis = cexRow)
if (!is.null(ylab)) 
    mtext(ylab, side = 4, line = margins[2] - 1.25)

Once you decide what you want, then hacking that code will get you a specific result. If you want the entire function rewritten, then ..... hire a consultant