In message <[log in to unmask]>, Nick Miller
<[log in to unmask]> writes
>In reply to Trevor Gray's enquiry, the test you are interested in is
>urinary sulphite, which is not a normal component of urine.
>Sulphite, either ingested as a food preservative or endogenously
>formed, is usually oxidised to sulphate prior to its excretion by the
>action of sulphite oxidase, a molybdenum-dependent enzyme.
>Sulphite thus appears in the urine in a) sulphite oxidase deficiency
>(extremely rare) b) Mb deficiency (not so rare as you might think)
>c) asthmatic hypersensitivity after the ingestion of sulpite-preserved
>foods. In Mb deficiency (b) the disappearance of sulphite from the
>urine after Mb administration is used as a functional test for Mb
>deficiency.
>
>Before I go on, this is one of the familiar chestnuts with which we
>are visited every few years, but it's very easy to measure urinary
>sulphite by either (1) the Merck kit (Merckoquant Sulfitest, the
>basis of which is its colour reaction with sodium nitroprusside,
>potassium ferricyanide and zinc sulphate) or (2) the decolorisation
>of pararosaniline (basic fuchsin - you'll find it in Bacteriology). Urine
>samples should be collected without preservative and, if there is
>bacterial contamination, a fresh random urine is better than a 24
>hour collection. In a normal urine sulphite should be undetectable.
>
>Sulphites (which is a generic term covering Na and K sulphite,
>bisulphite, and metabisulphite, as well as sulphur dioxide) are
>widely used as food preservatives and that is the key to the
>problem - some people ingest an awful lot of them and others are
>also hypersensitive to sulphites. I once worked (briefly) for a soft
>drinks concern who were adding so much sulphite to their orange
>cordial that it was dissolving away the aluminum caps before they
>could sell it to the kiddies at the cinema kiosks. Sulphites are
>also, for example, sprayed on supermarket lettuce to keep it
>looking fresh and crisp long after it would have been seen to have
>gone off.
>
>Sulphites cause degradation of thiamine (vitamin B1) and possibly
>the correlation with schizophrenia is that some such patients are in
>fact suffering from food hypersensitivity (or sulphite oxidase
>deficiency/Mb deficiency) to the consequent detriment of their
>nerve cell B1 levels.
>
>References:
>
>JIMD 6 (suppl 2) 95 (1983)
>Pediatrics 73, 631 (1984)
>BMJ 297, 105 (1988)
>Lancet 2, 644 (1988)
>
>No doubt there's been a few more over the past decade !
>
>Best wishes,
>
>Nick Miller,
>London
>
Thanks for comprehensive answer.
Frances Dryburgh was right as I have now received a photocopy of a
dogeared cutting dated 23.6.98 - not sure which paper - which reports
that at the annual meeting of the RCPsych in Belfast, a paper was
presented from Guy's and Thomas's on urine sulphite in patients with
schizophrenia. The paper showed "90% had high levels of sulphite in
their urine".
There are a number of groups looking for a metabolic defect associated
with schizophrenia. In Sheffield they are doing a lot of work with
polyunsaturated fatty acids, levels of which appear to be different in
patients with some psychoses.
Thanks to all who replied.
--
Dr. T.A. Gray
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|