Studies on Kinin Formation in Functional Vasodilatation of the Submandibular Salivary Gland in Cats

The submandibular salivary gland in cats has been perfused undcr conditions of constant volume inflow with red blood cells suspended in normal cat plasma. Such a method is favourable for studying the time course of changes in glandular vascular resistance. A 30 sec supra‐maximal stimulation of the chordo‐lingual nerve caused the vascular resistance to fall markedly within 1–6 sec. When the nerve stimulation was finished, a further decrease in perfusion pressure was usually observcd, whereafter a slow increase in vascular resistance took place. The rapidity with which the vascular response occurred indicates an initial direct action of true vasodilator nerve fibres. The second phase of the vasodilatation, outlasting the chorda stimulation itself, is claimed to be mediated by kinin formation in the activated gland: a) When the gland was perfused with normal cat plasma, so that resting perfusion pressure was low (under 55 mm Hg), then the vasodilator response to chorda stimulation changed, developing gradually and outlasting the nerve stimulation. b) Reduction of kininogen 2 in the plasma perfusate resulted then in a reduced vasodilator response to chorda stimulation. c) With no kininogen 2 in the cell‐free perfusate, stimulation of the chordo‐lingual nerve caused only a very small vasodilatation or no vasodilatation at all. d) Addition of partly purified kininogen 2 to such perfusate did then restore the chorda‐induced vasodilatation.