Free radicals and Aging (antioxidants)

[Peter H. Proctor]

In article <Pine.SOL.3.91.960710145914.21124D-100000 at interchg.ubc.ca> browley at UNIXG.UBC.CA (Brian Rowley) writes:
>From: browley at UNIXG.UBC.CA (Brian Rowley)
>Subject: Free radicals and Aging (antioxidants)
>Date: 10 Jul 1996 14:59:48 -0700


>The other thing to think about is that rodents have a greatly inferior
>antioxidant system to humans. Our blood is almost saturated with uric acid
>(sometimes it crystalizes in the joints to cause gout). We also do not
>produce our own vitamin C, unlike most rodents. It turns out that uric
>acid is a greatly superior antioxidant to vitamin C, or so I've heard.
>Vitamin C, in really high doses, actually increases free radicals, so I
>have also heard. So we humans perhaps traded vitamin C for uric acid
>somewhere along the way for that particular antioxidant niche, giving us
>greater longevity. And humans produce more SOD per gram of tissue when
>corrected for metabolic rate. What I'm trying to say is that just because
>antioxidants increase life expectancy of rodents by 30% does not
>necessarily imply that they will do the same for people. We have such a
>good system already, there is less to improve on. Something to consider
>anyway :->

       It gets even worse.   Uric acid is a good example.   Yes,  it is a good 
antioxidant and probably substtitutes for ascorbate in Human evolution.    
( BTW,  I originally suggested this,  he says modestly ).

      OTOH,  like ascorbate and other strong reducing substances  ,  uric acid 
can actually mediate radical oxidations by reducing oxygen to it radical 
forms.   In fact,  this may account for the pathogensis of hyperuricemic 
diseases such as the lesch-Nyhan syndrome.   Same with a lot of other 
so-called "antioxidants".   Such processes may actually contribute to some 
human diseases.     See P. Proctor,  Free Radicals and Human Disease,  in CRC 
Handbook of Free Radicals and Antioxidants,  Vol. 1 (1989 ) p211.

Peter H. Proctor, PhD, MD