We show for the first time that Ca(2+)-ATPase as an important, functionally active membrane protein of the apical plasma membrane is incorporated into the aposomal membranes and is released from the cells during apocrine secretion process.

Apocrine secretion is an alternative export pathway for proteins and was described especially for accessory sex glands of rodents and men. This mechanism is not as well characterized as the classical merocrine (eccrine) export. In the rat coagulating gland both secretion modes were observed, and several proteins were identified to be released by these two pathways. To obtain more data on the apocrine secretion mode, we established two culture models of the rat coagulating gland: primary epithelial cells and an organ culture system. The in vitro models were characterized with immunocytochemistry, electron microscopy and RT-PCR. The polarity of primary and passaged epithelial cells (passage 8) was proven by the detection of occludin, E-cadherin and beta-actin. The gland tissue pieces showed good maintenance after 1-week culture. Finally we demonstrated that the epithelial cells of both culture models are still expressing and producing apocrine and merocrine proteins. Using these two culture models for the rat coagulating gland, it is now possible to initiate studies on the apocrine secretion mechanism in vitro.

We showed for the first time that PMCA isoform 1b is released via aposomes of the epithelial cells of the rat coagulating gland and that the localization of PMCA1b in the epithelial cells is influenced by androgens.

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