Objectives

To define the effects of Isoproterenol, a sympathomimetic drug and β-receptor agonist that used for treatment of cardiac and respiratory diseases, on dog parotid and submandibular glands.

Materials & Methods

Twenty adult female stray dogs (range of b.w 19.9 ± 1.4 kg) were used as control and isoproterenol treated groups. Experimental group received daily intraperitoneal injections of 0.3 mg per kg isoproterenol-Hcl (Sigma Chemical Co.) dissolved in 1 ml of sterile distilled water for 20 days. The control group received 1ml of sterile distilled water in the same route. In the end of experiment, the animals were anesthetized with ketamine and authonized with over dose of Nesdonal. The parotid and submandibular glands were quickly excised. After weighting the glands and minced into 1cm cubes, they were placed in ten per cent buffered formalin as fixative for 24 hours, followed by alcohol dehydration and embedding in paraffin. Sections of glands were stained with haematoxylin- eosin and studied for determination of histomorphological changes.

Results

Chronic isoproterenol treatment for twenty days induced significant enlargement of the parotid and submandibular glands. There was marked variation in the degree of its enlargement, the submandibular and parotid glands showed 2.1 and 1.6 folds increase in wet weight as compared to control group. Using t -student test analysis, the weight changes were significant (P<0.05). After chronic of isoproterenol administration, the parotid gland had a little increase in cell size. Histological observations of the glands in treated group revealed greater degree of acinar cell enlargement (hypertrophy) while secretory granules in submandibular gland were larger than parotid gland. Following isoproterenol treatment, the cytoplasm of the hypertrophied acinar cells was peaked with many large pale-staining secretory granules and the nuclei were compressed toward the cell base. In isoprenaline treated group, histomorphological changes of secretory units of parotid gland observed rarely.

Conclusion

Histomorphological changes of parotid and submandibular glands is dependent on different regulatory pathway of these glands, which produces different patterns of secretion granules. The hypertrophy and hyperplasia of acinar cell related to both sympathetic and parasympathetic nerves. The sympathetic stimulation plays a major role in the induction of acinar cell hypertrophy while parasympathetic activity is most potent in initiating hyperplasia of the gland cells. However, a synergistic relationship exists between the two neural pathways because both systems must be intact and active for the maximum effect on secretory cells of salivary glands.

We suggested that, it is possible, the type of nerve supplying in secretory cells of dog submandibular gland is different from other animals but for clarify various aspects of cellular activity immunohistochemical studies are suggested.