Hydrogen sulfide is gaining acceptance as an endogenously produced modulator of tissue function. The present paradigm of H(2)S (diprotonated, gaseous form of hydrogen sulfide) as a tissue messenger consists of H(2)S being released from the desulfhydration of l-cysteine at a rate sufficient to maintain whole tissue hydrogen sulfide concentrations of 30 microM to >100 microM, and these tissue con...