Yes, I think it possibly could, because bine is salt that is used to preserve the meat and that's why we don't feed tuna in brine, rather we go for the oil based tuna, and I think there was something on the news recently about a little girl having an overdose of salt, but she had died (sorry, don't want to frighten you or anything!) and they found this out doing the autopsy on her. Can't you phone the vet and ask him if you're not going to go there until the morning and tell him what happened? I think an overdose of salt in a human can send your blood pressure soaring, and this may be what happened to your dog, but as long as she has got over it she should be ok, but I would definitely speak to the vet if you can just to be on the safe side.

welcome to dogweb

(have to say Jazz has had tuna in brine (although i do drain the brine out) and had no reaction at all )