Other relatively common forms of dysfunctional hemoglobin include sulfhemoglobin
The reversible binding of oxygen to sulfhemoglobin
and transient methemoglobinemia secondary to diarrhoea.
The components of Drabkin reagent lysed red blood cells and reacted with all forms of Hb except sulfhemoglobin
present in the sample, converting them to cyanmethemoglobin, a stable brownish-colored compound.
Exposure to sulfide caused no changes in the absorption spectrum, and there was no peak at 620 nm; this peak is characteristic of human sulfhemoglobin
in the visible region of the spectrum (van Assendelft, 1970; Carrico et al., 1978).
Other rare causes include sulfhemoglobin
(hydrogen sulfite poisoning, sumatriptan) and, as in this case, hemoglobin variants with reduced oxygen affinity (6).
Because sulfide (the sum of [H.sub.2]S, H[S.sup.-], and [S.sup.=] unless otherwise specified) is a potent inhibitor of mitochondrial cytochrome oxidase (Nicholls, 1975; Wilson and Erecinska, 1978; National Research Council, 1979) and can render hemoglobin nonfunctional through the formation of sulfhemoglobin
(Berzofsky et al., 1971; Carrico et al., 1978), it is potentially toxic to a variety of aerobic organisms.