Dietary protein quality alters ornithine decarboxylase activity but not vitamin B-6 nutritional status in rats.
Weanling male rats were fed diets that varied in protein quality (casein or wheat gluten) and vitamin B-6 (0.0, 0.5, 1.0 and 1.5 mg pyridoxine HCl/kg diet) to test the hypotheses that low protein quality would depress vitamin B-6 nutritional status and that activity of ornithine decarboxylase (ODC) would be a sensitive functional indicator of vitamin B-6 nutritional status. The wheat gluten diet depressed body weight gain approximately 17% at higher vitamin B-6 levels, as expected. However, vitamin B-6 nutritional status was not worse in gluten-fed compared with casein-fed groups, as evidenced by static measures (B-6 vitamer concentrations in plasma and tissues) and a functional indicator (tryptophan load test). The activity of ODC (holo- and total) in liver, kidney and small intestine did not vary significantly at the three higher levels of vitamin B-6 intake. In groups fed casein, total ODC activity in these tissues was two- to fivefold higher in rats fed diets containing 0.0 mg vitamin B-6/kg compared with higher B-6 levels, without corresponding differences in ODC mRNA abundance in liver and kidney. Concentrations of B-6 vitamers (except pyridoxal phosphate in plasma) increased linearly with dietary vitamin B-6 in plasma, liver, kidney and intestine. These data suggest that low quality protein fed as wheat gluten suppresses growth but not vitamin B-6 nutritional status, and that ODC activity is not a sensitive functional indicator of marginal vitamin B-6 status.
Sampson
D A
DA
Department of Food Science and Human Nutrition, Colorado State University, Fort Collins 80523, USA.
Harrison
S C
SC
Clarke
S D
SD
Yan
X
X
D000818:Animals; D001682:Biological Availability; D001835:Body Weight / Q000187:drug effects; D002851:Chromatography, High Pressure Liquid; D004044:Dietary Proteins / Q000494:pharmacology*; D007413:Intestinal Mucosa / Q000378:metabolism; D007668:Kidney / Q000378:metabolism; D008099:Liver / Q000378:metabolism; D008297:Male; D009752:Nutritional Status; D009955:Ornithine Decarboxylase / Q000378:metabolism*; D011736:Pyridoxine / Q000493:pharmacokinetics*; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D014018:Tissue Distribution
D004044:Dietary Proteins; D012333:RNA, Messenger; D009955:Ornithine Decarboxylase; D011736:Pyridoxine