Acetate stimulates secretion in the rabbit mandibular gland

Abstract

In isolated perfused rabbit mandibular glands undergoing stimulation with 0.8 microM acetylcholine, replacement of HCO3- with acetate (25 mM) increased fluid secretion by more than 100%. Other short-chain fatty acids, except for propionate, had a similar effect. We focused our further studies on acetate, and in order to find out the cause of its stimulatory effect we investigated whether acetate itself was transported. In the absence of any other transportable anions 25 mM acetate supported secretion at the same rate as 25 mM HCO3- or 25 mM Cl-, i.e. 20% of the control rate. In solutions containing acetate as the only major anion (146 mM), fluid secretion was maintained at about 50% of the control rate. Amiloride (1 mM) inhibited this secretion by about 90%. In glands perfused with acetate/Cl- solutions, when the stimulatory effect was normally observed, amiloride (1 mM) inhibited secretion by 50-60% and SITS (0.1 mM) had no effect. Probenecid reversibly inhibited 75% of secretion in these glands, but it also inhibited 92% of secretion in glands perfused without any acetate. Interestingly, the acetate effect was abolished in glands stimulated with a higher concentration of acetylcholine (80 microM). Results of this study suggest that acetate can be transported by salivary endpieces and that this transport involves an amiloride-sensitive Na+-H+ antiport. We postulate that acetate may in addition have some regulatory or modifier role in salivary secretion.