label: serotonin(out) + K(+)(in) + Na(+)(out) + H(+)(in) <=> serotonin(in) + K(+)(out) + Na(+)(in) + H(+)(out)
label_lc: serotonin(out) + k(+)(in) + na(+)(out) + h(+)(in) <=> serotonin(in) + k(+)(out) + na(+)(in) + h(+)(out)