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Developmental changes in lactase-phlorizin hydrolase precursor isoforms in the rat.
M A Dudley1, R J Shulman, P J Reeds
1USDA/ARS Children's Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, TX 77030.
Journal of Pediatric Gastroenterology and Nutrition
|October 1, 1992
Summary
The developmental decline in rat lactase activity is linked to shifts in enzyme precursor forms, not immunohistologic changes. As rats age, the mature lactase form decreases while a precursor form increases.
Area of Science:
- Biochemistry
- Developmental Biology
- Gastroenterology
Background:
- Lactase specific activity declines during rat development.
- Understanding the molecular basis of this decline is crucial for developmental and digestive studies.
Purpose of the Study:
- To investigate if developmental decline in rat lactase activity correlates with changes in enzyme precursor/mature forms.
- To examine immunohistologic changes in the jejunal mucosa during rat development.
Main Methods:
- Studied lactase activity in rat pups (10, 16, 22 days) and adult rats (nongravid, pregnant, lactating).
- Utilized SDS-PAGE to analyze molecular forms of immunoisolated lactase.
- Assessed relative quantities of 140-kDa (mature) and 200/220-kDa (precursor) lactase forms.
Main Results:
- Lactase activity was highest in suckling pups and increased in lactating adults.
- Three molecular forms of lactase (140, 200, 220 kDa) were identified.
- The proportion of the mature 140-kDa form decreased with age, while the 200-kDa precursor form increased.
Conclusions:
- The developmental decline in rat lactase activity is associated with a decrease in the mature enzyme form and a rise in a precursor form.
- Age-related changes in lactase molecular forms occur independently of reproductive status (pregnancy/lactation).
- Immunohistologic changes were not the primary driver of lactase activity decline.