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Effect of Ascorbic Acid Nutriture on Protein-Bound Hydroxyproline in Guinea Pig Plasma^1,2,

Graduate Division of Nutrition, University of Texas, Austin, TX 78712

This paper provides indirect evidence that ascorbate nutriture affects plasma concentrations of complement component Clq in the guinea pig. Clq is a protein with a hydroxyproline-rich region similar in structure to collagen. It is essential for complement-mediated lysis of pathogens and may also facilitate phagocytic activity of macrophages and neutrophils. Since Clq is the only hydroxyproline-containing protein in the euglobulin fraction of plasma, it can be quantified indirectly by precipitating this fraction, hydrolyzing it and estimating hydroxyproline colorimetrically. We investigated the effect of ascorbate nutriture on protein-bound hydroxyproline (PBH) in the euglobulin fraction of plasma of young male guinea pigs. The animals had been depleted of ascorbate for 3 wk to produce scurvy and then repleted (6 wk) as follows: 0.5, 2.0 and 10.0 mg ascorbate/100 g body weight per d or 10 g ascorbate per liter of drinking water. PBH values were significantly correlated (P < 0.001) with dietary ascorbate (+0.74) and with liver ascorbate (+0.75). Plasma PBH was significantly higher (P < 0.01, Scheffé's test) in guinea pigs fed ample ascorbate (10.0 mg/100 g body weight per day) or tissue-saturating levels (10 g/L of drinking water) than in those fed adequate (2.0 mg/100 g body weight) or suboptimal (0.5 mg/100 g body weight) levels. These data are consistent with the known biochemical role of ascorbic acid in hydroxyproline biosynthesis and suggest a possible link between ascorbate and the immune response via Clq.

KEY WORDS: • ascorbate • hydroxyproline • complement Clq

¹ Supported in part by grants from the University Research Institute, University of Texas, Austin, TX.

² Presented at the Federation of American Societies for Experimental Biology Annual Meeting, 1985, Anaheim, CA. Johnston, C. S., Cartee, G. D. & Haskell, B. E. (1985) Effect of ascorbic acid nutriture on plasma Clq levels in the guinea pig. Fed. Proc. 44, 1150 (abs. 4324).

Manuscript received 3 January 1985. Revision accepted 30 April 1985.