Abstract
Summary: Intestines of newborn and postnatal young of female rats fed diets containing 4% or 24% casein during pregnancy were infused in vivo with 50 mM 14C-labeled 1-aminocyclopentane-1-carboxylic acid (ACC), α-aminoisobutyric acid (AIB), glycyl-1-L-leucine (GL), or 8% 3H-histidine-labeled casein in 5% glucose and physiologic saline. The amounts of each material removed from the lumen or absorbed and the amount retained by the intestinal tissue were expressed as a total amount and per g body weight and per enterocyte.
Casein absorption was significantly reduced per absorptive cell in prenatally protein-deprived (PPD) young at birth, but there were no differences at 8 days of age. AIB absorption and retention were decreased in PPD newborn young compared to controls whether expressed as a total, or on the basis of body weight or per enterocyte. At 12 days, total retention and absorption were reduced in PPD young, but all other differences no longer existed. ACC absorption was reduced in PPD young, compared to controls, regardless of the means of expression. Retention of ACC per enterocyte was increased at birth compared to controls. These differences had disappeared by 8 days. GL retention was increased in PPD young compared to controls at birth, but not at 8 days.
The data on casein absorption indicate that newborn PPD young are handicapped at some point in the process of digestion and absorption of protein. At birth, amino acid absorption is also affected. Active transport of amino acids may be affected in some way, such as by an effect on carrier protein, by a deficit of available energy for active transport. The high retention of dipeptide per enterocyte may be the consequence of a decreased ability of the enterocytes of PPD young to hydrolyze the dipeptide or may be the result of increased incorporation of these materials into mucosal protein. There is apparently a marked difference between the effects of intestinal absorption of prenatal protein deprivation and those of postnatal malnutrition. It is suggested that the competence of the enterocytes are reduced in newborn PPD young whereas animals whose prenatal nutrition was normal would begin life with a larger complement of fully differentiated absorptive cells and might therefore be capable of greater adaptation to the nutritional deficit.
Speculation: The data presented demonstrate that maternal protein deficiency results in decreased absorption of protein and its digestion products in the intestine of newborn rat pups. This may contribute to an explanation of the postnatal growth retardation, high mortality rate, and reduced immunocompetence in these offspring. Further investigation is needed on the specific steps in the protein digestion and absorption process which are affected and on the procedures which might be used to compensate for the depressed absorption.
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Zeman, F., Fratzke, M. Protein, Dipeptide, and Amino Acid Absorption in the Young of Protein-deprived Rats. Pediatr Res 11, 972–977 (1977). https://doi.org/10.1203/00006450-197709000-00008
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DOI: https://doi.org/10.1203/00006450-197709000-00008