Levels of cellular retinol-binding proteins in the small intestine of rats during pregnancy and lactation.
The movement and metabolism of vitamin A is dependent on a number of specific carrier proteins. The small intestine contains both cellular retinol-binding protein (type two) (CRBP(II], restricted to the villus-associated enterocytes, and cellular retinol-binding protein (CRBP), present primarily in supporting mesenchymal cells. The content of these proteins in the small intestine of prepartum and postpartum Sprague-Dawley rats was determined by radioimmunoassay. Levels of CRBP(II), but not CRBP, changed dramatically during this period. Total content of CRBP(II) in the small intestine rose precipitously in late pregnancy and continued to rise throughout lactation to a peak at day 21 postpartum more than 300% greater than in nulliparous, nonpregnant controls. In contrast, total small intestinal weight and CRBP content increased only approximately 100% from late pregnancy to day 21 of lactation. CRBP(II) concentration in the proximal and middle segments of small intestine (expressed on a g wet tissue, mg protein, or mg DNA basis) remained at control levels through day 17 of pregnancy, increased 50-100% in late pregnancy, then rose markedly at parturition to levels two- to threefold greater than controls. CRBP(II) concentration was then maintained at a relatively constant elevated level during the remainder of lactation, but decreased markedly after weaning, approaching control levels within 1 week. The concentrations of CRBP(II) in enterocytes isolated from the proximal two-thirds of the small intestine from rats on day 20 of pregnancy and days 1 and 16 of lactation, expressed on a mg DNA basis, were similar and approximately 60% greater than controls.(ABSTRACT TRUNCATED AT 250 WORDS)
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Department of Biochemistry, Vanderbilt University Medical Center, Nashville, TN 37232.
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D000818:Animals; D004247:DNA / Q000378:metabolism; D005260:Female; D007421:Intestine, Small / Q000166:cytology / Q000378:metabolism*; D007774:Lactation / Q000378:metabolism*; D011247:Pregnancy; D011270:Pregnancy, Animal / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D011863:Radioimmunoassay; D051381:Rats; D011919:Rats, Inbred Strains; D012177:Retinol-Binding Proteins / Q000096:biosynthesis / Q000378:metabolism*; D054840:Retinol-Binding Proteins, Cellular
D012333:RNA, Messenger; D012177:Retinol-Binding Proteins; D054840:Retinol-Binding Proteins, Cellular; D004247:DNA