Current middleware database replication protocols take care of read-write conflict evaluation. If there are no such conflicts, protocols sanction transactions to commit. Other conflicts may arise due to integrity violation. So, if, in addition to the consistency of transactions and replicas, also the consistency of integrity constraints is to be supported, some more care must be taken. Some classes of replication protocols are able to seamlessly deal with the integrity support of the underlying DBMS, but others are not. In this paper, we analyze the support for integrity that can be provided in various classes of replication protocols. Also, we propose extensions for those that cannot directly manage certain kinds of constraints that are usually supported in DBMSs.