Effects of alterations in calcium concentrations on secretion and protein synthesis in cat submandibular salivary gland

Use of different derivatives of D-Val-Leu-Arg for studying kallikrein activities in cat submandibular glands and saliva

Glandular kallikrein shows a special selectivity for D-Val-Leu-Arg-4-methoxy-2-naphthylamide in comparison with other potential oligopeptide substrates and it provides a useful histochemical substrate, although the reaction may not always be specific. However, in cat submandibular saliva, a biochemical assay using the closely related D-Val-Leu-Arg-7-amino-4-trifluoromethylcoumarin (AFC) as substrate, which affords more sensitive detection, showed that soya bean trypsin inhibitor causes no inhibition. This indicates that there are unlikely to be contaminating enzymes competing for the substrate in this body fluid. Support for this observation has been gained by the useful new enzyme overlay membrane technique for fluorescent assessment of reactive bands of enzymes after isoelectric focusing, using membranes of cellulose acetate impregnated with D-Val-Leu-Arg-AFC. Comparison of results after isoelectric focusing of purified cat submandibular kallikrein with samples of cat submandibular saliva confirmed that the substrate is monospecific for kallikrein in saliva of the cat. This knowledge has enabled us to start assessing the dynamics of the secretion of kallikrein by the gland. Testing individual drops of saliva has shown that an amazingly rapid mobilization of kallikrein occurs in high concentrations on sympathetic nerve stimulation. The corresponding oligopeptide-based inhibitor D-Val-Leu-Arg-chloromethyl ketone was found to be strongly inhibitory of the amidase reaction by kallikrein but showed a low specificity for kallikrein. Nevertheless, its effects have been tested in vivo by the intravascular route and it caused an increase in the resting salivary vascular resistance whether administered close-arterially or intravenously. Thus, it would seem that a kallikrein-like protease does influence the background tone in the vessels and the source of this enzyme is thought to be mast cells.

Significance of adrenergic alpha-effect on salivary kallikrein secretion in the submandibular gland of the dog

The effects of the sympathetic nerve stimulation and the administrations of sympathomimetics on the secretion of salivary kallikrein induced by the chorda tympani stimulation were examined quantitatively and qualitatively in the submandibular gland of the dog. The secretion of salivary kallikrein may be mediated through both adrenergic alpha- and beta-receptors. The activities of salivary kallikrein secreted by either the chorda tympani stimulation or isoproterenol were not inhibited by soy bean trypsin inhibitor in vitro, but those secreted by the sympathetic nerve stimulation and noradrenaline or adrenaline were markedly inhibited in vitro. These results suggested that secretion of glandular kallikrein was induced by the chorda tympani stimulation and the sympathetic beta-stimulation, and secretion of plasma kallikrein was induced by the sympathetic alpha-stimulation.

Comparative studies on the effects of bradykinin and vagal stimulation on motility in the stomach and colon

The effect of bradykinin on gastric and colonic motility was studied in anaesthetized cats with volume recording devices and compared with the effects of vagal nerve stimulation. When administered intrarterially bradykinin caused a profound and prolonged gastric relaxation. Stimultaneously there was a marked and likewise prolonged colonic contraction. The gastric relaxation closely mimicked the atropine resistant relaxation elicited by vagal nerve stimulation. These effects could not be blocked by antiadrenergic drugs and it is suggested that bradykinin and the unknown transmittor substance(s) released on vagal stimulation act in a similar way on the gastric smooth muscles and that a kinin mechanism may be involved in the vagal response. As regards the colonic motor response it was shown that bradykinin does not reproduce the vagal motility effects on colon smooth muscle but mimicks closely the atropine resistant expulsive contraction elicited by activation of the pelvic nerves.