The endocrine regulation of milk lipid synthesis and secretion in tammar wallaby (Macropus eugenii) |
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Authors: | Joly H.L. Kwek Chakra Wijesundera Matthew R. Digby Kevin R. Nicholas |
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Affiliation: | 1. Department of Zoology, University of Melbourne, Parkville, Victoria 3010, Australia;2. Co-operative Research Centre for Innovative Dairy Products, Level 1, Melbourne, Victoria 3000, Australia;3. Food Science Australia, Sneydes Road (Private Bag 16), Werribee, Victoria 3030, Australia |
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Abstract: | Lipids in tammar milk are predominantly triacylglycerols, and the fatty acid composition varies during the lactation cycle. Little is known about the regulation of their synthesis. This study investigates the endocrine regulation of lipid synthesis in mammary explants from pregnant tammars. Treatment of mammary explants with insulin resulted in a high level of lipid synthesis, but the lipids accumulated in the cytosol. Culture with prolactin resulted in a small increase in lipid synthesis, but electron microscopy showed lipid globules were synthesized in the mammary epithelial cells and secreted into the lumen. Culture with both insulin and prolactin demonstrated elevated levels of synthesis and secretion of lipid. Analysis of the type of fatty acids synthesized in these mammary explants showed that the initiation of synthesis of C16:0, which also occurs in the first week of lactation, could be reproduced in the pregnant explants cultured with prolactin alone. However, treatment of mammary explants with hydrocortisone did not show a significant effect on lipid synthesis, secretion or the fatty acid synthesized. These results provide new information identifying the role of insulin and prolactin in regulating milk lipid synthesis and secretion in the tammar. |
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Keywords: | Tammar wallaby Mammary gland Lipid Fatty acid Synthesis Secretion |
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