Morphological and biochemical changes in the rat parotid gland after compensatory and isoproterenol-induced...

Enlargement of parotid glands can be induced in rats by treatment with isoproterenol (ISP) or by removal of the submandibular and sublingual glands. In this study, morphological changes in the enlarged parotid glands and qualitative changes in secreted proteins were examined in rats that had been treated with ISP for 10 days or that had been partially sialoadenectomized by removal of the submandibular/sublingual glands 2 weeks prior to killing. After ISP treatment or salivary gland ablation, secretory cells were enlarged and contained enlarged secretory granules that stained differently from granules in normal glands. Isoproterenol treatment induced the greatest enlargement of cells and granules. Even though gland structure was altered in both experimental groups, electrophoresis of saliva showed that submandibular/sublingual gland ablation did not lead to significant qualitative changes in secreted proteins, while ISP treatment induced major changes in the pattern of secreted protein. The results suggest that compensatory enlargement of the parotid glands and changes after ISP treatment are induced by stimulation of different regulatory pathways.