Development of a Clinically Applicable Protocol for Assessment of Hypoxic Response Through Measurement of the Endogenous Gasotransmitter Hydrogen Sulfide in Human Plasma.

BACKGROUND: Gasotransmitters are endogenously made, biologically active gases with unique physiological properties. In addition to participation in the hypoxic respiratory reflex of the carotid body, the gasotransmitter hydrogen sulfide (H(2)S) is thought to play a role in more localized vasodilatory hypoxic tissue responses. This pilot project describes a methodology suitable to the clinical environment that allows for H(2)S gas capture in human plasma utilizing the fluorescent trapping agent dansyl azide.

METHODS: Under an IRB-approved pilot project, 10 healthy male volunteers were spontaneously ventilated on room air, hypoxic (15% oxygen, 85% nitrogen), and hyperoxic (100%) gas mixtures through a nonrebreather system. Venous whole-blood samples were collected at both internal jugular and antecubital sites following 7 minutes of exposure to the tested oxygen environments. Resultant plasma aliquots were treated with dansyl azide and submitted to fluorescence reading (excitation 340 nm, emission 517 nm).

RESULTS: Compiled mean data from volunteer plasma samples demonstrated statistically significant findings (P<0.05) in measurement of increased fluorescent intensity between those samples collected under mildly hypoxic conditions compared with normoxic and hyperoxic samples submitted to the same laboratory criteria.

CONCLUSIONS: To study the role of H(2)S as a marker of hypoxic response in humans, a reliable, robust, and safe protocol amenable to standard hospital laboratory procedures is needed. Through modification to methodologies described in the biochemistry literature, this pilot project demonstrates the feasibility of utilizing a fluorescent H2S gas trapping agent for assessment of hypoxic response in humans within the confines of a typical clinical collection and analysis environment.