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Factors Affecting the Accumulation of Homocyst(e)ine in Rats Deficient in Vitamin B-6¹

Departments of Nutritional Sciences and Meat & Animal Science, University of Wisconsin, Madison, WI 53706

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.

KEY WORDS: • homocysteine • vitamin B-6 • cystathionine synthase

¹ Research supported in part by the College of Agricultural and Life Sciences and project number 133-C706 from the Food Research Institute, 1925 Willow Drive, Madison, WI 53706. This is paper number 821 from the Department of Meat and Animal Scienca.

² Present address: Dr. L. A. Smolin, UCLA Medical Center, CSC Box 16, 1000 W. Carson St., Torrance, CA 90509.

³ Reprint requests should be sent to N. J. Benevenga, University of Wisconsin-Madison, Room 1156 Animal Sciences Building. 1675 Observatory Drive, Madison, WI 53706, phone (608) 263-4313.

Manuscript received 2 May 1983.

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