Analysis of @entity1 milk was conducted to determine if free @entity1718 occur naturally or as a consequence of artifactual lipolysis after milk expression. Five mothers provided triplicate early morning milk samples on day 43 of lactation. Following extraction, lipid classes were separated by preparative thin layer chromatography and quantified by capillary gas liquid chromatography. Fresh milk samples collected with 20 volumes @entity3636 - @entity1042 (1:1, v/v) were analogous in total free @entity844 level and profile of @entity1718 to a duplicate sample collected with 0.4M @entity1098 and immediately frozen at -10 C. Low milk levels of free @entity1718 appear to exist naturally. During days 4-37 of lactation, four serial milk samples from 15 mothers were collected and frozen with 0.4M @entity1098 . The concentration of free @entity1718 in colostrum (0.03-0.5%, w/w) was lower than for subsequent days (0.3-2.5%, w/w). Additional samples were collected with and without a lipase inhibitor (0.4M @entity1098 ) and subjected to routine collection and storage procedures. Significantly different @entity844 profile and higher levels of free @entity1718 in milk collected without a lipase inhibitor added indicate that domestic freezing and/or thawing ruptures the fat globule membrane, allowing sn-1-stereospecific serum stimulated lipoprotein lipase contact with its @entity412 substrate. Standard procedures for collection of @entity1 milk for gavage fed @entity1 appears to stimulate artifactual lipolysis of milk @entity412 and subsequent release of free @entity1718 . The proposed relationship between dietary free @entity1718 and prolonged, unconjugated @entity3638 in the newborn is discussed with regard to the significance of preintestinal lipolysis.

Free @entity844 content of XXXX milk: physiologic significance and artifactual determinants.

@entity1 :: ('9606', 'Species') :: ['human', 'infants'] @entity844 :: ('CHEBI:35366', 'Chemical') :: ['fatty acid'] @entity1042 :: ('MESH:D000432', 'Chemical') :: ['methanol'] @entity3636 :: ('MESH:D002725', 'Chemical') :: ['chloroform'] @entity412 :: ('CHEBI:17855', 'Chemical') :: ['triglyceride'] @entity1718 :: ('MESH:D005227', 'Chemical') :: ['fatty acids'] @entity3638 :: ('MESH:D006932', 'Disease') :: ['hyperbilirubinemia'] @entity1098 :: ('MESH:D004492', 'Chemical') :: ['EDTA']
@entity1 :: (9606,Species) :: ['human']
