As far as I know of, there isn't a way Daisy. Is there a way you can try brass polish on the factory antique finish in a spot that won't show?
Is the antique brass you are speaking of, real brass?

Maybe you would be satisfied with the look of gold spray paint or faux brass?
Gold spray paint

Faux brass

Thanks for the responses. I could do a test in the future, right now the fixtures are in storage. Our contractor grossly under estimated our light fixture budget. All fixtures are supposed to be replaced (insurance) but there is no way we can do that on his budget, so I am trying to figure out how to save some of them and still have them work with the new colour-scheme, etc. I'm not even sure if they can be salvaged as water was pouring through them.

I know he is required to eat the cost if he underestimated, but he has been really wonderful so far (fingers x'd) in trying to get us what we want within our budget (while still making money himself, of course). I'd rather be creative where I can rather than just insisting he take a hit on it.

Graywings, thanks for the links. I have spray painted fixtures in less public rooms, but this would be in our kitchen and dining room, so I don't think I'd be happy with that option. I may just have to spend the summer searching for deals.

Check the wiring and paint them for now ... and when the budget allows, replace them.

Have you looked into have them replated in shiny brass? Actually they may know how to bring the shine back without replating them.