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Re: When dietary methionine and cysteine are low, what are the priorities?

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  • AndyCutler@aol.com
    ... deficient in ... live a ... restriction ... This study is completely irrelevant, off point, and misleading in the context of the autism mercury list.
    Message 1 of 2 , Jun 8, 2001
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      --- In Autism-Mercury@y..., Susan Owens <lwo@i...> wrote:
      > Listmates,
      >
      > This study gives a look at what happens if there is a reason for
      > metallothionein induction in someone who has become recently
      deficient in
      > sulfur, and is probably already deficient in glutathione.
      >
      > Of course, this is looking at an 8 day trial in animals that only
      live a
      > few years. The results might be quite different if the diet
      restriction
      > had been extended for months, or even through an entire lifetime.

      This study is completely irrelevant, off point, and misleading in the
      context of the autism mercury list.

      DIETARY INTAKE is only a surrogate for body composition. Some
      people's bodies hold onto the "sulfur" avidly, others spill it fast.
      The more appropriate question is WHAT IS SOMEONE'S PLASMA CYSTEINE OR
      BLOOD GLUTATHIONE LEVEL. Mercury intoxication is well known to
      decouple dietary intake from actual levels (we certainly spend enough
      time talking about that and its implications on list) so the paper
      below only has some hope of conveying useful information if diet is
      ignored and instead body levels of available thiols are considered.

      Interpreted as above, this paper suggests sulfation problems should be
      nonexistent in "high sulfur" people, which is contrary to clinical
      observations.

      Andy
      >
      > Susan
      >
      > 1: Toxicol Appl Pharmacol 1990 Feb;102(2):259-67
      >
      > Effect of sulfhydryl-deficient diets on hepatic metallothionein,
      glutathione,
      > and adenosine 3'-phosphate 5'-phosphosulfate (PAPS) levels in rats.
      >
      > Sendelbach LE, White CA, Howell S, Gregus Z, Klaassen CD.
      >
      > Department of Pharmacology, Toxicology and Therapeutics, University
      of Kansas
      > Medical Center, Kansas City 66103.
      >
      > Low dietary concentrations of methionine and cysteine are known to
      decrease
      > hepatic glutathione content. However, it is not known if restricting
      the
      > dietary
      > content of these sulfur containing amino acids also affects hepatic
      levels of
      > adenosine 3'-phosphate 5'-phosphosulfate (PAPS), the cofactor for
      sulfation, or
      > metallothionein, a protein rich in sulfhydryl groups. Rats were fed
      diets
      > lacking cysteine and containing various concentrations of methionine
      (0.15,
      > 0.3,
      > or 0.6%) for 8 days. Control diet contained 0.3% each of methionine
      and
      > cysteine. Hepatic glutathione levels were decreased approximately
      75% in rats
      > fed diets containing 0.15 or 0.3% methionine. In contrast, PAPS and
      hepatic
      > metallothionein concentrations were not decreased by the low
      sulfhydryl diets.
      > Additionally, rats on the various diets were challenged by the
      > administration of
      > ZnCl2 (3 mmol/kg. sc). In both control rats and rats maintained on
      > sulfhydryl-deficient diets, ZnCl2 increased hepatic metallothionein
      to the same
      > level. However, significantly lower levels of PAPS were observed
      after ZnCl2 in
      > rats receiving sulfhydryl-deficient diets than in controls. In
      summary,
      > restriction of dietary sulfhydryl markedly decreases the hepatic
      content of
      > glutathione and has a minor effect on PAPS concentration, but does
      not decrease
      > the basal hepatic concentration of metallothionein or its induction
      by ZnCl2.
      >
      > PMID: 2300970
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