Role of the cytoskeleton in secretory processes: lacrimal and salivary glands

Effects of vinca alkaloids on rat parotid and submandibular glands function in vivo

1. Vincristine (1 mg/kg) and vinblastine (2 mg/kg) were injected intraperitoneally into the rats, 24 hr before the experiments. 2. Animals were anesthetized with 50 mg/kg of sodium pentobarbital and saliva was collected from vincristine-treated, vinblastine-treated and control animals using 8 mg/kg of pilocarpine as secretagogue. 3. Parotid saliva was analyzed for protein, amylase and Ca2+ content, and submandibular saliva for flow rate, protein and Ca2+ concentration. 4. Saliva from two treated groups was significantly lower (P < 0.01) in flow rate, amylase and protein content than that of control group. Calcium level was significantly increased (P < 0.05) in treated animals. 5. It is concluded that the antisecretory effects of vinca alkaloids may be consistent with their actions on salivary cell microtubules.

Colchicine analogues that bind reversibly to tubulin define microtubular requirements for newly synthesized protein secretion in rat lacrimal gland

The role of microtubules in 3H-labeled protein secretion in rat lacrimal glands was probed by the use of colchicine and two of its analogues that reversibly bind to tubulin. These analogues were 2-methoxy-5-(2,3,4,4'-trimethoxyphenyl)-2,4,6-cycloheptatriene-1-o ne and 2,3,4,4'-tetramethoxy-1,1'-biphenyl, the latter having been synthesized for these studies. Immunofluorescence revealed that untreated exocrine acinar cells contained an intact microtubule network, which was totally abolished by drug addition. Subsequent drug removal restored the network for the two reversibly binding drugs--more rapidly so for the biphenyl, but this was not the case with colchicine. The protein-secretory process was examined by adding the three drugs at various stages--prepulse incubation, pulse, maturation, apical storage of granules, and discharge under cholinergic stimulation. Comparison with the kinetics of microtubular network restoration, which differed for the two reversibly binding drugs, led to the conclusion that the microtubular system is critical to the maturation phase of secretion.