My recollection of MOV specifications is the are often rated for AC operation I.e. In the US we might use a 130Vac MOV. While others are rated for DC operation. For most folks it is probably wise to follow those ratings. If you are really into MOV.s then you look to the curves.
I do not mean to imply that AC rated MOVs a different from DC rated MOVs, they are both physically the same parts, its just how the catalog presents the specifications.