RABBIT LACRIMAL ACINAR-CELLS IN PRIMARY CULTURE - MORPHOLOGY AND ACUTE RESPONSES TO CHOLINERGIC STIMULATION

Purpose. The rabbit lacrimal gland yields large numbers of viable acin ar cells that, viable exposed to carbachol, respond with accelerated p rotein release, fluid phase endocytosis (Lucifer yellow uptake), and N a/H antiport activation. The current study was undertaken to determine whether such cells exhibit similar responses after having been mainta ined in primary culture. Methods. Cells were isolated from 2-kg, juven ile male New Zealand White rabbits and maintained in a supplemented DM EM/Ham's F-12 medium for up to 72 hours. Results. Electron microscopy showed the organization of freshly isolated cells to be highly polariz ed, with secretory vesicles at one pole and nucleus at the ether; vesi cles were heterogeneous in size and in the electron density of their c ontents. The cells remained polarized after overnight culture, but the secretory vesicle population was more homogeneous in size and content , and the cells tended to aggregate. After 72 hours, roughly half the cells retained good morphology and cytoplasmic polarization, but the v esicles were enlarged and their contents less electron dense. Cells th at had been maintained overnight responded to the addition of 10 mu M carbachol with a 32.2% +/- 15.5% (n = 12, P <0.04) increase in the tot al amount protein released during a standard 20-minute incubation. Thi s represented a mean 125% increase in the temperature-dependent compon ent of protein release. The protein secretory response was decreased t o 14.6% +/- 6.1% (n = 3, P <0.07) for cells that had been maintained f or 72 hours. In the same samples, carbachol increased fluid phase endo cytosis by 38.3% +/- 8.1% (P <0.01) and 70.9% +/- 13.4% (P <0.025), re spectively. The protein secretory response was partially, and the endo cytic response fully blocked by 1 mM atropine. Conclusions. This model could be useful as a simplified system in which to study regulation o f acinar cell function over days, rather than hours, as is required in fresh tissue models.