The Journal of Nutrition Vol. 127 No. 5 May 1997, pp. 687-693
Copyright ©1997 by the American Society for Nutritional Sciences

Lactase Phlorizin Hydrolase Synthesis Is Decreased In Protein-Malnourished Pigs

Manuscript received 25 October 1996. Initial reviews completed 2 December 1996. Revision accepted 23 January 1997.

Mary A. Dudley, Linda Wykes^*, Alden W. Dudley Jr., Marta Fiorotto, Douglas G. Burrin, Judy Rosenberger, Farook Jahoor, and Peter J. Reeds

USDA/Agricultural Research Service Children's Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine and Texas Children's Hospital, Houston, TX 77030, ^* School of Dietetics and Human Nutrition, McGill University, Montreal, Canada and  Pathology and Laboratory Medicine Service, Veterans Affairs Medical Center and Baylor College of Medicine, Houston TX 77030

We have examined the effect of protein malnutrition on brush border (BB) lactase phlorizin hydrolase (LPH) synthesis in young pigs. Two groups of four 3-wk-old pigs were fed diets containing either 19 g soy protein, 63 g carbohydrate and 5 g fat per 100 g diet (a protein-sufficient diet) or 3 g soy protein, 85 g carbohydrate and 5 g fat per 100 g diet (a protein-deficient diet). After 8 wk of consuming the diets, pigs were infused intravenously with ²H₃-leucine for 8 h, then killed. The jejunum was collected for measurement of lactase activity, LPH mRNA abundance and the rate of LPH post-translational synthesis. Lactase activities did not differ between groups (mean 8.1 ± 1.2 µmol·min¹·g mucosa¹). LPH mRNA abundance relative to elongation factor-1 mRNA (the constitutive/reference mRNA) was significantly (P < 0.05) higher in well-nourished pigs (0.36 ± 0.03%) than in protein-malnourished pigs (0.21 ± 0.02%). The rate constants of BB LPH post-translational synthesis were also significantly higher in the well-nourished (103 ± 9%·d¹) than in the protein-malnourished pigs (66 ± 8%·d¹). Further, the absolute synthesis rate of BB LPH, a measure of the amount of enzyme synthesized per gram of tissue, was significantly higher in well-nourished than in protein-malnourished pigs (in arbitrary units, 892 ± 90 vs. 450 ± 34, respectively). Thus, protein malnutrition affects both LPH mRNA abundance and post-translational processing in young pigs.

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