Exocytosis in secretory cells of XXXX lacrimal gland. Peroxidase release from lobules and isolated cells upon cholinergic stimulation.

@entity9310 @entity10941 @entity26 @entity855 @entity1391 @entity3897 @entity3812 @entity35 @entity3984 @entity5402 @entity5713
Release of peroxidase from secretory cells of @entity35 lacrimal gland upon cholinergic stimulation was studied in vitro with single lobules and isolated cells (lacrimocytes). Isolated lobules, kept in Eagle's medium, remain structurally intact and reaction product of peroxidase is confined to cisternae of rough endoplasmic reticulum, elements of the Golgi apparatus, and all secretory granules. Morphologically, exocytosis occurs by membrane fusion and discharge of granule content. The highest rate of peroxidase released from lobules is observed at 10(-4) M @entity5402 . The specific activity of peroxidase released into the medium is fourfold higher as compared to the lobules. Release of peroxidase is suppressed by @entity3897 when added before or after the addition of @entity5402 . At 4 degrees C, no peroxidase release occurs upon cholinergic stimulation. The exocytotic release of peroxidase is dependent on energy supply, as indicated by substantial inhibition (at 37 degrees C) under anoxic conditions or in the presence of @entity9310 , @entity3984 , or @entity10941 . Furthermore, the process is sensitive to @entity3812 and @entity5713 . Isolated lacrimocytes, consiting of 95% secretory acinar cells, are prepared by digestion with collagenase, hyaluronidase, and trypsin. They retain the characteristic polarity of secretory cells in situ, and localization of peroxidase is the same as in lobules. Since isolated lacrimocytes respond to cholinergic stimulation in the same way as lobules, the receptors are not damaged by the isolation procedure and appear to be associated directly with the exocrine cell. @entity26 uptake by isolated lacrimocytes is about 14 nmol O2 X min-1 X 10(-6) cells; it is about doubled by uncoupling with @entity9310 . @entity26 uptake rises by 20-30% above the resting rate upon cholinergic stimulation. This additional uptake is suppressed by @entity3897 or by added cholinesterase, indicating that continuous receptor occupancy may be required for the energy demand by exocytosis. On the basis of the specific activity of peroxidase in the medium, the energy demand resulting from cholinergic stimulation is estimated to be 0.08 mumol @entity855 (or energy-rich @entity1391 bonds) per microgram of protein released from the lacrimocytes.
