(R)-lactate(in) + H(+)(in) <=> (R)-lactate(out) + H(+)(out)
(r)-lactate(in) + h(+)(in) <=> (r)-lactate(out) + h(+)(out)
(R)-lactate(in) + H(+)(in) <=> (R)-lactate(out) + H(+)(out)
(r)-lactate(in) + h(+)(in) <=> (r)-lactate(out) + h(+)(out)