title: Autoradiographic studies of the distribution of 35sulfate label in ferret trachea: effects of stimulation.
abstract: Na2(35)SO4 is among the common isotopic mucin precursors used to label airway secretory cells and monitor their active discharge in response to drugs. Previous work has established that 35S is taken up by multiple cell types in the trachea, yet there is no direct evidence linking 35S release with secretory activity by any specific cell type. In this study, we have used autoradiography to identify the sites of uptake and release of 35S in ferret trachea. Confirming work performed in other species, we found uptake sites include surface epithelium (ciliated and goblet cells), submucosal glands (serous and mucous cells) and cartilage. Extending these findings using a "pulse-chase" protocol, we found that 35S turns over very rapidly in ciliated but not submucosal gland cells or cartilage. Specific grain density over epithelium declined from 0.12 +/-0.006 grains/micron 2 immediately after the pulse to 0.05 +/- 0.004 grains/micron 2 at 4 h. In contrast, corresponding figures for the glands and cartilage showed no spontaneous loss of label during the same period. At 4 h, when the epithelium contained very little 35S label, we exposed tracheal rings in vitro to neurotransmitter receptor agonists (bethanechol, phenylephrine, and isoproterenol; all at 10(-5) M). Counts in the medium (determined by scintillation spectrometry) increased 2-3 times in response to each agonist. These increases were prevented by preincubating tracheal rings with appropriate antagonists. Autoradiography showed that stimulated glands contained many fewer silver grains than untreated or antagonist-blocked glands. In contrast, neither cartilage nor epithelium showed decreased labeling after stimulation. These results indicate that (a) sulfated glycoconjugates turn over rapidly in the tracheal epithelium and may account for much sulfated material spontaneously released into organ culture medium and into the tracheal lumen, and (b) 4 h after Na2(35)SO4 incubation, the major source of 35S-labeled macromolecules released from ferret trachea by neural agonists is the submucosal glands.
mesh_terms: D000818:Animals; D001345:Autoradiography; D002356:Cartilage / Q000378:metabolism; D004848:Epithelium / Q000378:metabolism; D005289:Ferrets; D066298:In Vitro Techniques; D008297:Male; D008854:Microscopy, Electron; D010277:Parasympathomimetics / Q000494:pharmacology; D013431:Sulfates / Q000378:metabolism*; D013566:Sympathomimetics / Q000494:pharmacology; D014018:Tissue Distribution; D014132:Trachea / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure
chemical_list: D010277:Parasympathomimetics; D013431:Sulfates; D013566:Sympathomimetics