-ADRENERGIC EFFECTS ON COMPOSITION OF PAROTID SALIVARY SECRETION OF SHEEP ON FEEDING

¹ School of Veterinary Science, University of Melbourne, Parkville, Victoria, Australia 3052
² Department of Veterinary Physiology, University of Sydney, NSW Australia 2006

Observations were made in sheep, before and after fresh food was given during teasing with food and after rumination, on the flow of parotid saliva and its protein, Mg²⁺, K⁺, Na⁺ and Cl^- concentrations. The animals studied had either a cannulated or fistulated parotid salivary duct. Parotid salivary flow, protein, Mg²⁺, K⁺ and Cl^- increased markedly following feeding. The increases in protein and Mg²⁺, but not in flow, were largely blocked by the I.V. administration of propranolol (1 mg.kg^-1). Whereas the actual ingestion of food was associated with large increases in protein (up to 42·5 times, to as high as 1760 µg.ml^-1 of saliva), teasing with food caused relatively minor increases in parotid saliva. There were slight, if any, changes in protein concentration during the increased parotid salivary flows of rumination, whether chewing was on the same side or contralateral to the cannulated parotid salivary duct. It is concluded that a -adrenergic mechanism previously demonstrated in acute experiments contributes to increases in the secretion of protein of the parotid saliva when sheep eat. There was a close correlation between the concentrations of protein and of Mg²⁺ but not of the other electrolytes studied.