If you ask if it is possible to use "Mercado Pago" in itch.io, the answer is no.
If what you want is to suggest that it be incorporated as an official payment method within itch.io, it is best to do so in the suggestions subforum.
https://itch.io/board/580406/ideas-feedback
Personally I doubt that they will incorporate it, the administrator said that adding new payment systems is something complex that takes time and "mercado pago" has no advantage over paypal or payoneer.