Osanai, S; Mokashi, A; Rozanov, C; Buerk, DG; Lahiri, S*

Journal of the Autonomic Nervous System [J. AUTON. NERV. SYST.], vol. 63, no. 1-2, pp. 39-45, Mar 1997

The hypothesis that H sub(2)O sub(2) plays a critical role in hypoxic chemoreception in the cat carotid body (CB) was tested using a perfused-superfused preparation in vitro, measuring chemosensory discharge and CB tissue P sub(O2) (P sub(tiO2)). According to the hypothesis NADPH mediated. P sub(O2) dependant increase in H sub(2)O sub(2) production would hyperpolarize the glomus cell, decreasing the chemosensory discharge. Thus, lactate and aminotriazole which would increase H sub(2)O sub(2) concentration, would decrease the chemosensory discharge during hypoxia. However, 2.5-5.0 mM lactate and 25 mM aminotriazole did not diminish the hypoxic response. But, 2.5 mM lactate decreased the chemosensory discharge during normoxia which can be explained by an increase of CB P sub(tiO2). Diethyldithiocarbamic acid (5 mM), which blocks the conversion of superoxide to H sub(2)O sub(2), also diminished the chemosensory discharge, presumably due to an increased CB P sub(tiO2). Menadione (increasing H sub(2)O sub(2)) and t-butyl hydroperoxide irreversibly decreased the chemosensory discharge, and the data are not useful. H sub(2)O sub(2) increased the P sub(O2) of the perfusate, and therefore could not be tested against P sub(O2). Thus, perturbation of endogenous or exogenous H sub(2)O sub(2) did not provide any evidence for its critical role in O sub(2) chemoreception.