HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) Interpretive Summary Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Ernens, I. Articles by Larondelle, Y. Search for Related Content PubMed PubMed Citation Articles by Ernens, I. Articles by Larondelle, Y.

Short Communication: Ability of Cultured Mammary Epithelial Cells in a Bicameral System to Secrete Milk Fat

I. Ernens^*,,,1, R. Clegg^*, Y.-J. Schneider and Y. Larondelle

^* Hannah Research Institute, Hannah Research Park, Ayr, KA6 5HL, Scotland, UK
Laboratoire de Biochimie Cellulaire, and
Unité de Biochimie de la Nutrition, Institut des Sciences de la Vie, Université catholique de Louvain, B-1348 Louvain-la-Neuve, Belgium

¹ Corresponding author: isabelle.ernens{at}crp-sante.healthnet.lu

Mammary epithelial cells from lactating cows were cultured onto inserts coated with type I collagen. Every second day, the rates of fatty acid synthesis and secretion were determined by measuring the amount of [¹⁴C]-labeled sodium acetate incorporated into lipids over a 4-h period. The [¹⁴C]-containing lipids were identified by thin layer chromatography fractionation. In parallel, the integrity of the cell layer was evaluated by measurement of transepithelial electrical resistance. The integrity increased progressively to reach a maximum after 8 d of culture. Cells incorporated acetate into lipids; 1.34% of acetate was incorporated into lipids produced by freshly isolated cells. This percentage decreased to 0.5% after 2 d of culture. Moreover, this capacity decreased with the duration in culture; on d 8, the rate of incorporation dropped to about 3% of that on d 2. In the cell extracts, the [¹⁴C]-labeled lipids were mainly triglycerides, although the proportion of diglycerides and phospholipids progressively increased as a part of total newly synthesized lipids. The proportion of triglycerides decreased 0.66 times between d 2 and 8 when the proportion of diglycerides and phospholipids increased 1.33 and 2.18 times, respectively. About 28% of the newly synthesized lipids were secreted within 4 h of incubation. Around 65 to 85% of these labeled lipids were found in the apical compartment, suggesting a partially vectorial secretion. But 58 to 80% of labeled lipids found in the apical and basolateral medium were free fatty acids. Functional tight junctions and incorporation of labeled fatty acids into triglycerides are not compatible with an inferred status of complete dedifferentiation of the cell layer. Moreover, triglyceride secretion seems compromised, probably due to the lack of an appropriate cell environment and cell shape.

Key Words: lipid secretion • lipogenesis • mammary cell • transepithelial electrical resistance