The use of liposomes as encapsulating agents for feeding juvenile Pacific oysters (Crassostrea gigas)

• Main Author: Parker, Robert S.
• Other Authors: Selivonchick, D. P., Food Science and Technology, Oregon State University. Graduate School
• Format: Doctoral or Postdoctoral Thesis
• Language: English; unknown
• Published: Oregon State University
• Subjects: Liposomes; Oyster culture; Crassostrea gigas
• Online Access: https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/0r967737k

The ingestion, uptake, and metabolism of liposomes by juvenile Pacific oysters (Crassostrea gigas) were studied by several methods in an effort to assess their potential as encapsulating agents. Liposomes composed of egg phosphatidylcholine-cholesterol-stearylamine (7:1:2) formed readily and appeared stable in 20°/oo seawater. Radiotracer studies with liposomes made with ¹⁴C-labeled cholesterol or phosphatidylcholine showed uptake of up to 40% of the dose in 24 hrs, with the majority of uptake occurring in the visceral mass. Only slight amounts of label were observed in adductor muscle or mantle tissue. Absence of label in free fatty acids in oysters fed liposomes made with di[l-¹⁴C] palmitoyl phosphatidylcholine indicated a lack of significant amounts of fatty acid hydrolysis from phospholipid in the stomach or lumen of the digestive diverticula. However, radioactivity was observed in lipid other than phosphatidylcholine, including triglyceride, phosphatidylethanolamine, and an unidentified polar lipid. Radioactivity in these lipids resided exclusively in the fatty acids, indicating breakdown of the ¹⁴C-phosphatidylcholine via acyl transfer. To examine metabolism of liposome-encapsulated substances, [1-¹⁴C]glucose and [U-¹⁴C]amino acids were entrapped and fed to oysters. Label from glucose appeared largely in a choloroform-methanol-insoluble fraction, with little radioactivity recovered in the lipid or soluble aqueous fractions. Most label from amino acids was recovered in trichloroacetic acid-precipitable protein. Control oysters given the same amounts of non-encapsulated [1-¹⁴C] glucose or [U-¹⁴C]amino acids as in liposome trials showed (1) the same uptake of label from free amino acids in comparison with encapsulated glucose, and (2) increased uptake of free, amino acids in comparison with encapsulated amino acids. Label from free glucose or amino acids entered the same fractions as encapsulated label. Evidence for intracellular uptake of liposomes was obtained with fluorescence microscopy after feeding ...