Plasma-kinins and adrenergic vasodilatation in the submandibular salivary gland of the cat

Endothelium-derived vasodilator responses to sympathetic stimulation of the submandibular gland in the cat

1. The extent to which vasodilator responses to electrical stimulation of the sympathetic innervation, in the submandibular gland of the cat, depend upon release of endothelium-derived relaxing factor (EDRF) within the gland has been investigated in anaesthetized cats given N-nitro-L-arginine methyl ester (L-NAME) which specifically blocks the synthesis of EDRF from arginine. 2. Close intra-arterial infusions of L-NAME (> or = 100 mg kg-1) produced a steady and significant rise in mean aortic pressure together with a steady increase in basal submandibular vascular resistance over the next 20-30 min. It also reduced, but failed to abolish, the vasodilatation which occurs during intermittent stimulation of the sympathetic innervation (20 Hz for 1 s at 10 s intervals) together with the after-dilatation which occurs immediately after a period of continuous stimulation of these nerve fibres (2 Hz). 3. In cats pretreated with the beta-blocker propranolol (> or = 1.0 mg kg-1) both vasodilator responses were reduced, but persisted until L-NAME was administered, whereupon both were abolished. 4. It is concluded that release of EDRF within the submandibular gland of the cat contributes to the basal tone of the vasculature and is responsible for the alpha-adrenergic vasodilator responses to stimulation of the sympathetic innervation, but not for the beta-adrenergic vasodilator responses.

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.

Tissue hyperosmolality as a causal factor in vasodilatation following sympathetic stimulation of the submandibular gland

In a previous investigation, parasympathetic activation of the submandibular gland in the cat was found to cause a considerable increase of regional tissue osmolality, the degree of which was related to the evoked functional hyperemia; intra-arterial hypertonic infusion to the resting gland producing tissue hyperosmolality of similar magnitudes caused graded and marked dilatations (Lundvall and Holmberg 1974). It was concluded that hyperosmolality contributes significantly to the functional hyperemia response. In the present study evidence is presented to indicate that tissue hyperosmolality is a mediator of the dilatation associated with sympathetic activation as well. An increase of tissue hyperosmolality, as traced in the venous effluent, was found at all frequencies of sympathetic stimulation (2-16 Hz). At high stimulation rates it sometimes exceeded the resting control level by more than 20 mOsm/kg H2O. There was a direct relation between the degree of venous hyperosmolality and the hyperemia response observed immediately after cessation of stimulation. Comparison of the dilator effects evoked by sympathetic stimulation and by hypertonic infusion to the resting gland indicated that tissue hyperosmolality is an important causal factor for the nerve induced dilatation, especially at low and moderate stimulation rates.

Rat submandibular gland kallikreins: purification and cellular localization

1 Four submandibular gland kallikreins (E.C.3.4.21.8) were isolated by chromatography on DEAE-Sephadex A-50 and hydroxyapatite, followed by gel filtration and electrofocusing. The pI values were 3.87, 3.96, 4.07 and 4.16, and a common molecular weight of 34,000 was found. 2 The kallikreins were localized by direct immunofluorescence with an antibody to rat urinary kallikrein, to the granular tubules, striated duct cells and some main duct cells in the submandibular gland, and to striated duct cells in the sublingual gland. Kallikrein was not found in acini and stroma. 3 Several non-kallikrein esterases present in the submandibular gland reacted with the antibody to rat urinary kallikrein. The antibody was made monospecific for kallikrein by absorption with the crossreacting esterases. 4 We suggest that kallikrein is produced in striated duct cells. Granular tubules, which are differentiated from striated duct cells, have preserved the ability to produce kallikrein. These cells also store large quantities of kallikrein.