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Fluid-phase transcytosis in the primate epididymis in vitro and in vivo
C H Yeung1, T G Cooper, G F Weinbauer
1Max Planck Clinical Research Unit for Reproductive Medicine, Münster, FRG.
Abstract:
Ligated tubules from the corpus epididymidis of men and monkeys were incubated in medium containing horseradish peroxidase (HRP) as a marker for fluid-phase endocytosis. HRP was localized by light and electron microscopy after 0, 15, 30 and 60 min of incubation. Movement between the cells was prevented by tight junctions, but bypass of this barrier was apparently achieved by an intracellular vesicular mechanism leading to a time-dependent appearance of HRP in the lumen. Uptake of HRP into basal cells and capture by the lysosomal apparatus of principal cells were also observed. HRP-filled vesicles also appeared in the basal, mid and apical cytoplasm of epithelial cells in the caput 1 h after injection of the tracer into the epididymal circulation of the monkey, suggesting that this pathway also operates in vivo.
Insights
Researchers studied fluid-phase endocytosis in the epididymis using horseradish peroxidase (HRP). They found an intracellular vesicular mechanism allows HRP to bypass tight junctions and reach the lumen in both men and monkeys.
Area of Science:
- Reproductive Biology
- Cell Biology
- Histology
Background:
- The epididymis plays a crucial role in sperm maturation and transport.
- Understanding the mechanisms of fluid and solute transport within the epididymis is essential for reproductive health.
- Endocytosis is a key cellular process involved in transport across epithelial barriers.
Purpose of the Study:
- To investigate the mechanism of fluid-phase endocytosis in the epididymis.
- To determine if horseradish peroxidase (HRP) can be used as a tracer for endocytosis in epididymal tubules.
- To explore the in vivo and in vitro pathways of HRP transport in the epididymis of men and monkeys.
Main Methods:
- In vitro incubation of ligated epididymal tubules from men and monkeys with HRP.
- Localization of HRP using light and electron microscopy at various time points (0, 15, 30, 60 min).
- In vivo administration of HRP into the epididymal circulation of monkeys to observe transport.
Main Results:
- Tight junctions prevent paracellular movement, but an intracellular vesicular mechanism facilitates HRP transport to the lumen.
- Time-dependent appearance of HRP in the lumen suggests an active transport process.
- HRP uptake by basal cells and lysosomal capture by principal cells were observed, along with HRP-filled vesicles in caput epididymal epithelial cells in vivo.
Conclusions:
- An intracellular vesicular pathway, likely endocytosis, is responsible for bypassing tight junctions and transporting HRP across the epididymal epithelium.
- This mechanism allows for the transport of fluid-phase markers from the lumen into the epididymal epithelium.
- The observed pathway in vitro and in vivo suggests a conserved mechanism for epididymal transport in primates.