Studies on the difference of salivary response to catecholamines in developing rat submandibular gland

Abstract

The response of submandibular salivary secretion in rats of several age groups was examined with the administrations of α and β-adrenergic agonists.Submandibular saliva was collected intraorally from male Sprague-Dawley strain rats of 2 to 8 weeks of age as immature, and 12-15 weeks of age as mature. Noradrenaline (2mg/kg) or phenylephrine (6mg/kg) as α-adrenergic agonists, and isoproterenol (30mg/kg) as β-adrenergic agonist were administered i. p. for collecting saliva.Results obtained were as follows: The response of salivary secretion, such as salivary volumes, flow rate and protein concentration, in the rats of 7-8 weeks did not significantry differ from that of mature rats. In the response to β-adrenergic agonist by disc electrophoresis, types of secreted proteins in 6-week rats resembled that in mature rats. In the response to a-adrenergic agonists by disc electrophoresis, types of secreted proteins in 7-week rats resembled that in mature rats. However, types of secreted proteins in the rats of 2 to 5 weeks of age were similar to the case of β-adrenergic agonist. The result of analysis of isoelectric focusing indicated that secreted proteins by α-adrenergic agonist in 7-week rats resembled those in mature rats. By chronic noradrenaline (1mg/kg) administration, the growth rates of body weights and submandibular wet weights in 4-week rats were slightly suppressed as compared with those in the control rats.