Reversal of diet-induced changes in adenylate cyclase activity and fatty acid composition of rat submandibular salivary gland lipids.

This study sought to determine if the diet-induced changes in submandibular salivary glands can be reversed. Two groups of male weanling Sprague-Dawley rats were fed purified diets containing 9% butter + 1% corn oil (group I, control) or 9% ethyl ester concentrate of n-3 fatty acids + 1% corn oil (group II, experimental). After 5 weeks of feeding the respective diets, rats in group I were divided into two subgroups: Ia, which was maintained on the control diet, and Ib, which was shifted to the experimental diet for the reversal study. The rats in the experimental group were kept on their original diet. After five further weeks of feeding, the rats were killed, and membranes from submandibular glands were prepared and assayed for adenylate cyclase activity and for the fatty acid composition of total phospholipids. Changes characteristic of feeding n-3 fatty acids, including a significant increase in membrane fluidity as measured by the degree of unsaturation of fatty acids, were observed in the total phospholipids of membranes from the experimental group. The adenylate cyclase activity was two- to three-fold higher in membranes of rats fed the experimental diet (group II) than the control diet (group Ia). Whereas the diet-induced changes in fatty acid composition and membrane fluidity were largely reversed (group Ib, reversal study), changes in adenylate cyclase activity were only partially reversed. The results suggest that, in addition to the fatty acid composition and membrane fluidity, other factors may also be important in modifying adenylate cyclase activity.