Xref: utzoo sci.bio:2340 sci.chem:497 sci.med:12463
Path: utzoo!attcan!uunet!kitty!larry
From: larry@kitty.UUCP (Larry Lippman)
Newsgroups: sci.bio,sci.chem,sci.med
Subject: Re: Butane death
Summary: Methane and hemoglobin
Message-ID: <3400@kitty.UUCP>
Date: 22 Sep 89 04:12:26 GMT
References: <89262.194442RAV103@PSUVM.BITNET> <3398@kitty.UUCP> <4633@ursa-major.SPDCC.COM>
Organization: Recognition Research Corp., Clarence, NY
Lines: 48

In article <4633@ursa-major.SPDCC.COM>, dyer@spdcc.COM (Steve Dyer) writes:
> In article <3398@kitty.UUCP> larry@kitty.UUCP (Larry Lippman) writes:
> >While methane will directly combine with hemoglobin to
> >for methemoglobin, which competes with oxyhemoglobin, I suspect that
> >the butane molecule is too large to undergo such a substitution with
> >hemoglobin.
> 
> I had always understood that methemoglobin is simply an oxidized form
> of hemoglobin, with the ferrous iron (Fe++) in heme oxidized to the
> ferric (Fe+++) state.  I don't see where methane comes in.  Methane
> certainly isn't one of the traditionally-enumerated toxic agents which
> cause methemoglobinemia, such as nitrites and certain aromatic amines.

	Congratulations - you caught me in a typographical error.  I had
meant to say "methanehemoglobin" instead of "methemoglobin", which is
entirely different and much more common.

	However, my typo had no real bearing on the context of my article,
which would be clear had you included the sentence preceding that which
you quoted: "With respect to direct toxic affects of butane, these may
well be minimal."

	In any event, methane does happen to combine with hemoglobin in
a manner analgous to that of carbon monoxide.  While the effect is rarely
seen in humans and certainly would occur in no instance other than toxic
exposure to methane, it has been identified in ruminant animals (like sheep
and cattle).  Methane gas is produced in the rumen and reticulum and is
usually expelled via eructation, although some of the expelled methane is
inhaled and thereby absorbed through the lungs.  In particular, even more
methane is absorbed under the pathological condition known as "bloat",
where the methane concentration and vapor pressure increases to the point
where it is absorbed by blood vessels in the rumen, reticulum, omasum and
abomasum.  Using methane tagged with carbon-14, methanehemoglobin has been
identified.  While most of these studies have appeared in the veterinary
rather than "human" literature, there was a study on this topic by
Dougherty et al which appeared in the American Journal of Physiology
in the mid 1960's.

	While the absorption and metabolism of methane and certain related
hydrocarbons in humans is a bit arcane, I happen to be familiar with
some literature on the topic as a result of developing analytical methods
and instruments for evaluation of human occupational exposure to various
chemical agents.

<> Larry Lippman @ Recognition Research Corp. - Uniquex Corp. - Viatran Corp.
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