Localisation of esteroproteases in 'resting' salivary glands from different species and the effects of the organophosphorus inhibitor E600

Abstract

The distribution of reaction sites for esteroproteases has been assessed in 'resting' salivary glands from rats, guinea-pigs, cats, dogs and rabbits using the new substrate N-acetyl-L-methionine alpha-naphthyl ester (Lexow et al. 1979). Two main types of activity were observed in the parenchyma. 1) Condensed staining was present on the luminal sides of certain ducts in some, but not all, glands, and this type of staining was always most conspicuous in the submandibular glands of each species. It is likely that this periluminal esteroprotease activity arises from secretory enzymes that will pass into the saliva. Their greater presence in submandibular glands may have association with specialised licking activities. 2) Variable diffuse cytoplasmic staining was present in certain acinar cells from some, but not all, glands. This was most pronounced in the mucous cells of zygomatic glands from dogs. It is considered that the enzymes demonstrated in acinar cells are involved in processing secretory products rather than in being secretory themselves. The possibility that this includes 'signal peptidase' is discussed. Ductal activity in rats, cats and guinea-pigs had some relationship with sites of tryptophan staining but not in rabbits or dogs. Any relationship with acinar staining was less evident. Mast cells, showing strong esteroprotease staining, were present in variable numbers in the different glands. Preliminary attempts to qualify the enzymes being demonstrated were made by using the inhibitor E600. This substance inhibited all activity in acinar cells from each species, and in rabbits and dogs it also inhibited the ductal activity as well. However, in rats and guinea-pigs it had little or no effect on the ductal activity and in cats it had only a small inhibitory effect on the ductal activity. E600 had no obvious inhibitory effects on mast cell activity.