The goal of the proposed research is to obtain basic information on the mechanisms of delivery of vitamin A to the mammary gland during lactation, and on cellular retinoid binding proteins that may facilitate intracellular transport and metabolism of retinol in the breast. Two major specific aims are proposed in which the lactating rat will serve as our model.
In Aim 1, we will determine the relative roles of chylomicron remnants and serum retinol-binding protein (RBP) and in delivering vitamin A to the mammary gland during lactation. We will test the hypothesis that uptake of retinol from RBP is quite constant over a wide range of dietary vitamin A, whereas uptake from the chylomicron remnant is variable and directly related to dietary consumption of vitamin A. To test this model, we will conduct a series of experiments in which lactating rats will receive an intravenous test dose of chylomicrons that have been labeled in vivo with 3H-retinyl esters. Remnant metabolism and uptake into mammary tissue will be measured as a function of time after administration, the dose of total chylomicron lipid, and the amount of chylomicron vitamin A. Experiments will also be conducted to determine whether local lipolysis is necessary for uptake of remnant retinyl esters by the breast, and whether retinyl esters are hydrolyzed and reesterified prior to secretion in milk. Complementary experiments on the uptake of 3H-retinol bound to serum RBP will also be conducted.
In Aim 2, we will initiate studies on the cellular form of retinol-binding protein (CRBP) in the lactating mammary gland. Using ELISA and immunocytochemical techniques, we will determine whether CRBP in this tissue is identical to that of other organs such as liver, the subcellular distribution of CRBP in tissue fractions, and the cellular distribution of CRBP in the lactating mammary gland. We will also investigate whether CRBP participates in the metabolism (esterification) of retinol in the breast, and whether the amount of CRBP or its distribution varies with vitamin A nutritional status, or with the developmental state of the mammary gland before and during the lactation period. Information to be developed in each of these specific aims will provide insight into the mechanisms by which retinol is metabolized and transported across the breast during lactation.

Agency
National Institute of Health (NIH)
Institute
Eunice Kennedy Shriver National Institute of Child Health & Human Development (NICHD)
Type
Research Project (R01)
Project #
5R01HD016484-08
Application #
3313698
Study Section
Metabolism Study Section (MET)
Project Start
1982-04-01
Project End
1993-03-31
Budget Start
1989-04-01
Budget End
1990-03-31
Support Year
8
Fiscal Year
1989
Total Cost
Indirect Cost
Name
Allegheny University of Health Sciences
Department
Type
Schools of Medicine
DUNS #
City
Philadelphia
State
PA
Country
United States
Zip Code
19129
Ross, A C (1993) Cellular metabolism and activation of retinoids: roles of cellular retinoid-binding proteins. FASEB J 7:317-27
Randolph, R K; Winkler, K E; Ross, A C (1991) Fatty acyl CoA-dependent and -independent retinol esterification by rat liver and lactating mammary gland microsomes. Arch Biochem Biophys 288:500-8
Randolph, R K; Ross, A C (1991) Vitamin A status regulates hepatic lecithin: retinol acyltransferase activity in rats. J Biol Chem 266:16453-7
Randolph, R K; Ross, A C (1991) Regulation of retinol uptake and esterification in MCF-7 and HepG2 cells by exogenous fatty acids. J Lipid Res 32:809-20
Ross, A C (1990) Separation of fatty acid esters of retinol by high-performance liquid chromatography. Methods Enzymol 189:81-4
Pasatiempo, A M; Ross, A C (1990) Effects of food or nutrient restriction on milk vitamin A transfer and neonatal vitamin A stores in the rat. Br J Nutr 63:351-62
Ross, A C (1990) Measurement of acyl coenzyme A-dependent esterification of retinol. Methods Enzymol 189:442-5
Pasatiempo, A M; Bowman, T A; Taylor, C E et al. (1989) Vitamin A depletion and repletion: effects on antibody response to the capsular polysaccharide of Streptococcus pneumoniae, type III (SSS-III). Am J Clin Nutr 49:501-10
McCloskey, H M; Glick, J M; Ross, A C et al. (1988) Effect of fatty acid supplementation on cholesterol and retinol esterification in J774 macrophages. Biochim Biophys Acta 963:456-67
Marinari, L; Lenich, C M; Ross, A C (1987) Production and secretion of retinol-binding protein by a human hepatoma cell line, HepG2. J Lipid Res 28:941-8

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