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The role of exocytosis in the apocrine secretion of milk lipid globules in mouse mammary gland during lactogenesis
Author(s) -
Metka Kralj,
Nada Pipan
Publication year - 1992
Publication title -
biology of the cell
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.543
H-Index - 85
eISSN - 1768-322X
pISSN - 0248-4900
DOI - 10.1016/0248-4900(92)90142-n
Subject(s) - apocrine , exocytosis , secretion , lipid droplet , globules of fat , vesicle , mammary gland , biology , myoepithelial cell , microbiology and biotechnology , lactation , cytoplasm , secretory vesicle , medicine , endocrinology , membrane , biochemistry , milk fat , immunology , anatomy , pregnancy , immunohistochemistry , genetics , food science , cancer , breast cancer , linseed oil
Summary— Functional relations between exocytotic vesicle membranes, plasmalemma and milk fat globule membranes (MFGM) were studied during the final stages of mouse mammary gland differentiation, in the gland during full lactation and in the postpartum gland in which the synthesis of secretory products was partly inhibited by application of 2‐Br‐α‐ergokryptin. Analysis of ultrathin sections, freeze‐fracture replicas, scanning electron microscopy and application of a cytochemical marker filipin showed that the apocrine secretion of lipid globules was closely related to the exocytosis of milk proteins. During the last days of gestation the secretion of lipid globules resulted from many exocytotic events of the secretory vesicles that accumulated and fused around the cytoplasmic lipid droplets. Seldom the lipid droplet protruded partly into the gland lumen and a part of its surface became covered with the apical plasmalemma. Although apical plasmalemma became more important in the formation of MFGM in the postpartum period, we could still confirm a direct contribution of secretory vesicle membranes to the final detachment of the lipid globule. The application of 2‐Br‐α‐ergokryptin hindered the apocrine secretion of the lipid globules and a situation similar to the situation in the prepartum gland was observed.