The effects of long-term treatment with salmeterol and salbutamol on the flow rate and composition of whole saliva in the rat

The effect of long-acting β2-radrenoceptor agonists on salivary glands and saliva secretion has not been studied before. Sprague-Dawley rats were given either the long-acting β2- agonist salmeterol, 1 mg/kg body wt per day or the short-acting agonist salbutamol, 5 mg/kg per day. Saline solution was used as control. After 18 days pilocarpine-stimulated saliva was collected, and after 21 days saliva was collected after stimulation with isoproterol and pilocarpine in combination. The saliva was analysed for total protein, amylase, hexosamine, sialic acid, sodium, potassium and calcium. At day 25 the salivary glands were extirpated and weighed. The weight of the parotid glands increased significantly after both salmeterol and salbutamol treatment, approx. 40%; the submandibular gland weights were not affected by either β2- agonist treatment. Pilocarpine-stimulated salivary flow rate was increased in the salbutamol, but not in the salmeterol, group. In the salmeterol group the concentration of sialic acid was increased and that of calcium was decreased. In saliva stimulated with pilocarpine and isoproterenol in combination, the concentrations of total protein, amylase and calcium were decreased after salmeterol. In the salbutamol group, total protein and potassium were decreased. The ratio sialic acid: total protein was increased at both saliva collections in both β2-agonist groups. It is concluded that rats treated chronically with the long-acting β2 adrenoceptor agonist salmeterol have an impaired secretion of salivary proteins and calcium and that the effect resembles that of salbutamol.