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Feeding Colostrum Rapidly Alters Enzymatic Activity and the Relative Isoform Abundance of Jejunal Lactase in Neonatal Pigs^1,2,

USDA/ARS Children's Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, TX 77030

Our objective was to determine the short-term effects of feeding colostrum and mature milk on the enzyme activity and relative isoform abundance of lactase in neonatal pigs. We studied newborn pigs that were fed colostrum, mature milk and water for 6 h (Study 1). We also studied unfed pigs shortly after birth, and newborn pigs fed either colostrum or mature milk for 24 h (Study 2). The specific activity (µmol·min^-1·g protein^-1) of lactase in a jejunal mucosal homogenate and a purified membrane fraction was lower in pigs fed colostrum than in unfed newborns or those fed either milk or water. However, after 24 h, total jejunal lactase activity (µmol·mol^-1), jejunal mass and protein content were higher in the colostrum- and milk-fed pigs than in the unfed newborns. In colostrum-fed pigs, the reduction in lactase specific activity after 6 h was associated with 1) a marked increase in the relative abundance of a 180-kDa protein, which was shown to be one of three pro-lactase isoforms, and 2) a lower relative abundance of the 160-kDa isoform, considered to be the mature form of the enzyme. Our evidence suggests that feeding either colostrum or mature milk increases total jejunal lactase activity. The reduction in both the specific activity and abundance of the mature isoform in conjunction with an increased relative abundance of the 180-kDa pro-lactase isoform suggests that feeding colostrum alters the post-translational processing of intestinal lactase in neonatal pigs.

KEY WORDS: • lactase • colostrum • pigs • neonatal • development

¹ This work is a publication of the U.S. Department of Agriculture/Agricultural Research Service Children's Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine and Texas Children's Hospital, Houston, TX. This project has been funded in part with federal funds from the U.S. Department of Agriculture, Agricultural Research Service under Cooperative Agreement no. 58-6250-1-003. The contents of this publication do not necessarily reflect the views or policies of the U.S. Department of Agriculture, nor does mention of trade names, commercial products or organizations imply endorsement by the United States government.

² The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 USC section 1734 solely to indicate this fact.

³ To whom correspondence and reprint requests should be addressed.

Manuscript received 28 February 1994. Revision accepted 6 June 1994.