title: Factors affecting the accumulation of homocyst(e)ine in rats deficient in vitamin B-6.
abstract: Factors that may affect the concentration of accumulated homocyst(e)ine in rats deficient in vitamin B-6 were studied. Hepatic cystathionine synthase activity in vitamin B-6 deficient rats was 41.5% of control and plasma protein-bound and free homocyst(e)ine concentrations were significantly increased; however, among deficient rats there was no correlation between the concentration of homocyst(e)ine and the activity of hepatic cystathionine synthase. The plasma protein-bound homocysteine concentration did not fluctuate with time of day, but a decrease in bound homocysteine was found when blood was sampled repeatedly from the same animal during a 24-hour period. A 24-hour fast resulted in a reduction in plasma homocyst(e)ine to concentrations not different from those of control animals. The protein content of the diet affected growth but not food intake of rats. Feeding a 10% versus a 60% casein diet did not change the concentration of accumulated homocyst(e)ine. Of the factors examined, only food restriction significantly affected plasma homocyst(e)ine concentration in rats deficient in vitamin B-6. It is speculated that decreased and sporadic food intake in rats deficient in vitamin B-6 may be responsible for the large fluctuations in homocyst(e)ine concentration observed in these animals over time.
mesh_terms: D000818:Animals; D002940:Circadian Rhythm; D003541:Cystathionine beta-Synthase / Q000378:metabolism*; D006710:Homocysteine / Q000378:metabolism*; D006711:Homocystine / Q000378:metabolism*; D006836:Hydro-Lyases / Q000378:metabolism*; D008099:Liver / Q000201:enzymology*; D008297:Male; D008954:Models, Biological; D011485:Protein Binding; D051381:Rats; D026681:Vitamin B 6 Deficiency / Q000378:metabolism*
chemical_list: D006710:Homocysteine; D006711:Homocystine; D006836:Hydro-Lyases; D003541:Cystathionine beta-Synthase