Studies on kinin formation in functional vasodilatation of the submandibular salivary gland in cats

Effect of sodium restriction and corticosteroids on glandular kallikrein in plasma and in the submandibular gland

We investigated whether sodium restriction or mineralocorticoid influence the release of submandibular kallikrein into the blood and/or the concentration of kallikrein in glandular tissue. For this we measured submandibular gland blood flow, arterial and submandibular gland venous kallikrein, and kallikrein in glandular homogenates of male Sprague-Dawley rats after one week of either low sodium or deoxycorticosterone acetate (DOCA) treatment. We also studied the effect of dexamethasone on the concentration of kallikrein in gland tissue and peripheral plasma. Kallikrein in plasma and in homogenates was measured by radioimmunoassay. Blood flow was determined by timed collections of venous outflow. Kallikrein release was calculated as the arteriovenous difference in kallikrein times the rate of submandibular gland plasma flow. The concentration of kallikrein in arterial plasma, the basal submandibular kallikrein release into blood, and the concentration of kallikrein in submandibular gland tissue were all higher during low sodium than during normal sodium intake (20.1 +/- 3.6 ng/ml vs 10.7 +/- 0.5, p less than 0.05; 0.40 +/- 0.09 ng/min/100 g bw vs 0.18 +/- 0.02, p less than 0.05, and 81.6 +/- 5.5 micrograms/mg protein vs 65.1 +/- 4.0, p less than 0.05, respectively). In contrast, DOCA treatment did not affect the concentration of kallikrein in arterial plasma, the basal release of kallikrein from the submandibular gland into blood, or the concentration of kallikrein in the gland. Dexamethasone in doses that did not affect the normal growth of the animals had no significant effect on the concentration of kallikrein either in submandibular gland tissue or in peripheral plasma.(ABSTRACT TRUNCATED AT 250 WORDS)

Studies on the atropine-resistant sacral parasympathetic vascular and motility responses in the cat colon

1. Pelvic nerve stimulation in atropinized cats elicits a sustained contraction of the proximal colon and a relaxation of the rectum. Concomitantly there is an immediate but transient vasodilatation which is followed by recurrent increases and a slight post-stimulatory hyperaemia. Direct stimulation of the pelvic nerve produces secretion of colonic kallikrein and activation of the plasma kinin system. The present study examines whether Trasylol, which inhibits the kinin system, affects the atropine-resistant responses observed on pelvic nerve stimulation. 2. After I.V. or close I.A. administration of Trasylol, the initial vasodilatation on pelvic nerve stimulation was markedly reduced and in a few experiments completely blocked. The recurrent blood flow increases and the post-stimulatory hyperaemia observed on prolonged stimulation were completely abolished. In contrast the proximal colonic contraction and the rectal relaxation appeared unchanged after Trasylol. 3. The reactivity of the vascular bed after Trasylol injection was studied by recording the changes of vascular resistance following sympathetic vasoconstrictor fibre activation and infusion of bradykinin before and after Trasylol injection. The responses were quantitatively unchanged excluding an unspecific interference with nervous transmission or vascular smooth muscle reactivity. 4. The results show that the atropine-resistant vasodilatation in the cat colon as elicited by pelvic nerve stimulation is partly abolished by a kallikrein inhibitor. This observation lends further support to the hypothesis that kinins might be involved in this response. The motor response, however, appears not be dependent on such a mechanism.

Vasomotor effects of facial nerve stimulation: noncholinergic vasodilation in the eye

The effect of facial nerve stimulation on ocular blood flow was studied in rabbits. The intracranial part of the facial nerve was stimulated electrically and the regional blood flow was measured with labelled microspheres. Effects on the intraocular pressure were determined in a separate series of experiments. Stimulation increased choroidal blood flow by about 200%. The blood flow of the iris and the ciliary processes also increased. The blood flow of the eyelids and the nictitating membrane increased by approximately 1000%, and the blood flow of Harder's gland increased by about 200%. The blood flow of the tongue and the submandibular gland also increased. The increase in the uveal blood flow could not be abolished by a cholinergic or ganglionic blockade. Ganglionic blockade abolished most of the increase in the blood flow of the eyelids, nictitating membrane and Harder's gland; the cholinergic blockade seemed less effective. The intraocular pressure increased with a mean value of 6 mmHg during optimal (20-30 Hz) stimulation. The increase could not be prevented by cholinergic blockade. Much of the increase in uveal blood flow seemed to be caused by stimulation of unconventional nerves. It is suggested that these nerves may be peptidergic using VIP as a transmitter and lacking a hexamethonium sensitive synapse between the site of stimulation and the eye. Their nature--afferent or efferent--remains unknown. A great part of the increase in blood flow of the eyelids, nictitating membrane and Harder's gland seemed to be due to other mechanisms involving nerves with a peripheral synapse.

Characterization of kallikrein from human saliva isolated by use of affinity chromatography

Kallikrein was isolated from paraffin stimulated saliva by use of two steps affinity chromatography. A610-fold purification of the enzyme was achieved by use of Sepharose 4B conjugated with soy bean trypsin inhibitor and pancreatic trypsin inhibitor. The isoelectric point of kallikrein was found to be pH 4.3 and the molecular weight was calculated to be about 38.000 by gel filtration on a AcA44 Ultrogel column. The enzyme had a pH optimum at pH 8.6 using BAEE and TAME as substrates. The michaelis constant for kallikrein on these two substrates was 4.0-10(-4) M and 5.5-10(-4)M. respectively.

Human saliva kallikrein. Biological properties of saliva kallikrein isolated by use of affinity chromatography

Kallikrein purified from whole human saliva was studied for its influence on leucocyte migration and kinin generating capacity. The kallikrein had a leucotactic effect on neutrophil leucocytes in the presence of 2% serum albumin. This leucotactic effect could be inhibited by Trasylol. The study showed that kallikrein liberated kinin from the precursor kininogen in dog plasma. Maximal release of kinin was achieved after 4 min of incubation. The kinin generating capacity of the enzyme was studied at different concentrations of kininogen. A maximum kinin release at 11.2 mug bradykinin per mg enzyme per minute was found.

Two phases of chorda-lingual induced vasodilatation in the cat's submandibular gland during prolonged perfusion with Locke solution

The effect of stimulation of the chorda-lingual nerve on the venous flow has been studied in cat submandibular glands perfused with Locke solution for 2-4 hr. When trains of pulses at 25 Hz were given for 1-5 sec, two distinct phases of vasodilatation were observed: a rapid initial phase of high amplitude and a slower developing more prolonged phase of smaller amplitude. Repeated stimulations did not lead to a reduction of the vasodilatory response. A close relationship was found between the duration and magnitude of the second phase of vasodilatation and the duration and magnitude of the post-stimulatory, active reuptake of potassium. When the active reuptake of potassium was prevented either by ouabain (which inhibits active transport) or by atropine (which abolishes the stimulation induced loss of potassium) the second phase of vasodilatation was severely reduced, while the initial phase remained virtually normal. It is concluded that the initial phase of vasodilatation probably is mediated by vasodilator nerve fibres. The second phase is perhaps causally related to the post-stimulatory, active transport of cations. An involvement of bradykinin formation is highly unlikely under the given experimental conditions.

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.