creatinine(in) + H(+)(out) <=> creatinine(out) + H(+)(in)
creatinine(in) + h(+)(out) <=> creatinine(out) + h(+)(in)
creatinine(in) + H(+)(out) <=> creatinine(out) + H(+)(in)
creatinine(in) + h(+)(out) <=> creatinine(out) + h(+)(in)