Effect of essential fatty acid deficiency on acyl group composition, membrane fluidity and adenylate cyclase activity in plasma membranes of rat submandibular salivary glands.

The effects of a marginal and severe deficiency of essential fatty acids (EFA) on the fatty acid composition, fluorescence polarization of diphenylhexatriene (DPH) and adenylate cyclase activity were studied in plasma membranes of rat submandibular salivary glands (SMSG). Three groups of male weanling Sprague-Dawley rats were fed ad libitum EFA-deficient (EFAD), marginally EFA-deficient (MEFAD) or the control diets. Rats were killed after 8-17 wk of feeding and plasma membranes were prepared from the SMSG and the assayed for basal and fluoride-stimulated adenylate cyclase activity. In membranes prepared from EFAD and MEFAD rats, the fluoride-stimulated enzyme activity was 30-35% higher than that of the control group. Lower double-bond index of phospholipids in plasma membranes of the SMSG from EFAD and MEFAD rats was observed, suggesting a lower fluidity compared with the control group. Higher fluorescence polarization of DPH in membranes of EFAD and MEFAD rats was more evidence of lower fluidity. It is suggested that higher adenylate cyclase activity in SMSG of rats fed EFAD or MEFAD diets may be related to lower membrane fluidity. Fluoride-stimulated enzyme activity and fatty acid composition of membrane lipids were restored to normal values after feeding the control diets for 6 wk to the EFAD and MEFAD rats.