The relationship between low leucocyte ascorbic-acid levels and tyrosine metabolism in the elderly.
Twenty-seven elderly men aged 69-94 years had tyrosine tolerance tests measured before and after receiving ascorbic acid 1 g daily for four days. There was a significant rise in the fasting and half-hourly mean plasma tyrosine levels after ascorbic acid administration in those subjects with an initial leucocyte ascorbic-acid level (LAA) below 15 micrograms/10(8) w.c.c. The peak of the tyrosine tolerance curve was also advanced following administration of ascorbic acid in those subjects with an initial LAA below 15 micrograms/10(8) w.c.c. A further ten elderly men aged 73-89 years had simultaneous measurements of the circadian rhythms of LAA, plasma cortisol and plasma tyrosine levels before and after receiving ascorbic acid 1 g daily for four days. All ten subjects showed a peak LAA level at 5 p.m. when saturated with vitamin C but there was no significant correlation between plasma cortisol changes and plasma tyrosine changes. Possible explanations for the results are discussed.
D000368:Aged; D000369:Aged, 80 and over; D001205:Ascorbic Acid / Q000032:analysis*; D002940:Circadian Rhythm; D005260:Female; D006801:Humans; D006854:Hydrocortisone / Q000097:blood; D007962:Leukocytes / Q000032:analysis*; D008297:Male; D014443:Tyrosine / Q000097:blood / Q000378:metabolism*
D014443:Tyrosine; D001205:Ascorbic Acid; D006854:Hydrocortisone