José Qués

I've already posted it. I'm just waiting an answer.
I'll wait a bit here, maybe someone can help me here.

Ok, I have an Image in 8 bits per channel mode on Photoshop. When I try to save it doesn't let me select the A8 R8 G8 B8 option.
Why I can't do it? There's a special mode that I have to choose to make this option available?
Only the XRGB (leading zero) it's availabe and I need the leading Alpha option.