Comparative analysis of dipsogenic effects of systemic and intracerebral injection of angiotensin II to rats after carotid glomectomy

Systemic administration of angiotensin II after carotid glomectomy produced a less pronounced dipsogenic effects (consumption of water and NaCl solution) compared to sham-operated control animals. Injection of angiotensin II into the lateral cerebral ventricles of the same glomectomized rats increased water and NaCl consumption to a level surpassing that of sham-operated animals. The number of drinking acts and comfortable grooming acts decreased in glomectomized animals after systemic administration of angiotensin II, but increased after its intracerebral injection compared to the control. The results confirm the hypothesis that carotid chemoreceptors, as the peripheral component of the renin-angiotensin system, participate in the mechanisms of angiotensin-induced thirst, “salt appetite”, and associated behavioral forms (comfortable grooming) synergically with the central cerebral receptors. __________ Translated from Byulleten’ Eksperimental’noi Biologii i Meditsiny, Vol. 142, No. 7, pp. 8–12, July, 2006     

Impaired drinking to angiotensin II after subdiaphragmatic vagotomy in rats

Rats received total bilateral subdiaphragmatic vagotomy and, one month later, were fitted with chronic intravenous or intracerebroventricular cannulas. The vagotomized rats showed much reduced drinking compared with controls during intravenous infusion of angiotensin II. Their drinking to intracerebroventricularly administered angiotensin II was, however, less affected. The possible role of the vagus nerve in the mediation of angiotensin and other types of drinking is discussed.     

Long-term immune reactivity to pre-S(2)-antigen after acute hepatitis B infection

We investigated sera from 39 patients, taken 1-8 years after recovery from acute hepatitis B for anti-pre-S(2) by Western blotting and for anti-HBs by radioimmunoassay. Anti-pre-S(2) antibodies were found in 27 out of 39 sera (69%) with the highest frequency in sera with anti-HBs greater than 100 IU/I (92%). However, sometimes sera with low anti-HBs titres showed a strong response in Western blotting. Acute hepatitis sera were also investigated from a limited number of patients (n = 14). Anti-pre-S(2) antibodies were found during antigenaemia (four out of six patients) and within 3 months after the maximum of alanine amino transferase (ALAT) (seven out of ten patients). Anti-pre-S(2) is an early antibody. It remains in the circulation for many years similar to but independent of anti-HBs.     

Perivascular injury leads to a reduction in vascular reactivity of the collared and to an enhancement on contralateral carotid artery of rats.

BACKGROUND: The first response to perivascular injury is observed in the adventitial layer. The purpose of this study was to determine the time course of vascular reactivity alterations after collar injury in rats. We also analyzed the relation between adventitial layer injury and vascular responsiveness to vasoconstrictor agents. METHODS: Wistar rats had a silicone collar positioned around the carotid artery. The ipsilateral and contralateral arteries were morphologically analyzed 4, 7, 14 and 28 days after injury, and cumulative concentration-response curves to phenylephrine (Phe), angiotensin II (Ang II) and KCl were obtained for arteries isolated from collared and sham-operated groups. RESULTS: Inflammatory cells and fibroblasts were observed in the adventitial layer of collared arteries 4, 7, 14 and 28 days after injury. Intimal thickening was observed in collared arteries only 14 and 28 days after perivascular injury. A decrease in maximum effect values (Emax) for Phe, Ang II and KCl was observed in the collared artery when compared with the contralateral artery at all times after injury, whereas an increase in vascular responsiveness was observed in the contralateral artery 4 days after injury. CONCLUSIONS: The impairment of the contractile response preceded the intimal thickening. The compromise of vascular reactivity coincided with the presence of inflammatory cells and angiogenesis in the adventitial layer. The enhancement of the efficacy and potency of Ang II and Phe in collared-contralateral arteries 4 days after collar placement may be related to a receptor-mediated compensatory mechanism stimulated by the collar injury.     

Behavioral effects of angiotensin II and angiotensin II-(4-8)-pentapeptide in rats

One nM of angiotensin II (AII) or angiotensin II-(4-8)-pentapeptide [AII(4-8)] given intracerebroventricularly did not affect locomotor and exploratory behavior of rats in open field. AII significantly increased and AII(4-8) did not affect vertical activity of animals in electromagnetic motimeter. Neither of the peptides influenced horizontal activity in the motimeter. Both peptides intensified stereotypy produced by apomorphine and amphetamine. AII significantly improved, while AII(4-8) did not affect, consolidation of memory of the correct way to food in T-maze. Similarly, AII increased and AII(4-8) did not change the rate of acquisition of conditioned avoidance responses in a shuttle-box. Of the two examined peptides only AII significantly improved retrieval of memory of the passive avoidance behavior. The results show that AII(4-8) influences central dopaminergic system but, unlike its parent peptide AII, has no apparent effect on memory.     

The paraganglia within the carotid bifurcation regions of young and old spontaneously hypertensive rats (SHR) after exposure to chronic hypobaric hypoxia. II. The carotid body-like organs

The following paraganglia in the carotid bifurcations regions of spontaneously hypertensive rats (SHR) were studied: Endoneural paraganglia within the external carotid nerve, the carotid sinus nerve, the glossopharyngeal nerve, and the pharyngeal branch of the vagus nerve, the so-called periadventitial type I cells, and so-called miniglomera. Number and distribution of these paraganglia vary among different individuals. After chronically hypobaric hypoxia the volume of these paraganglia was increased but their number remained unchanged. The increase of volume was dependent on the duration of hypoxia. There were no differences between young and old SHR when the hypoxia-time was the same.     

Morphology of the carotid sinus wall in normotensive and spontaneously hypertensive rats

The morphology of the carotid sinus region of the internal carotid artery was studied in spontaneously hypertensive rats (SHR) at 5, 8, 16, and 24 weeks of age. The carotid sinus region occupied the proximal millimeter of the internal carotid artery, and was easily recognizable by the presence of an extensive adventitial capillary plexus, which was absent on adjacent arteries (e.g., common and external carotid arteries). Methylene blue-stained whole-mount preparations showed the extent of baroreceptor nerves over the sinus. Baroreceptor fibers terminated in distinctive bulbous-like endings, which, at the ultrastructural level, were filled with mitochondria. No differences were noted in the sinus adventitial capillary network or baroreceptor distribution between SHR and age-matched Wistar-Kyoto (WKY) normotensive control animals. With the onset of a significant rise in SHR blood pressure, the carotid sinus wall increased in thickness and total vessel size. The wall/lumen ratios were significantly larger in the SHR than in age-matched WKY ratios in all age groups. SHR carotid sinus vessel enlargement was uniform throughout the vessel tunics, with no significant change in the proportion of the tunica media occupied by smooth muscle cells. The increase in the carotid sinus wall thickness associated with increasing hypertension could affect the ability of the sinus to distend and may play a secondary role in the maintenance of hypertension by compromising baroreceptor nerve ending sensitivity.     

Prostacyclin (PGI2) activity in rat kidney-stimulated by angiotensin II.

Prostacyclin (PG X, PG I₂) activity can be found in renal tissue as indicated by platelet aggregation inhibition. The activity of the medullal tissue in terms of wet weight is significantly higher (P < 0.01) than that of the cortex. The activity decreases with time, and disappears within one hour nearly completely. Boiling for 30 sec destroys the inhibitory effect of the prostacyclin on platelet aggregation. Angiotensin II is able to stimulate the prostacyclin availability of the tissue after incubation for 3 min. Addition of angiotensin II to platelet rich plasma (PRP) has no significant effect on the ADP induced platelet aggregation. The spontaneous generation of prostacyclin as well as that stimulated by angiotensin II can be suppressed by previous incubation of the tissue with a prostaglandin synthetase inhibitor such as Ketoprofen. The tissues which have only a small amount of inhibitory activity upon incubation in buffer show an increased platelet aggregation inhibitory effect after adding to PRP. A significant difference between medulla and cortex is found in this assay as well. The different release of prostacyclin can not be related to different endothelial surface area, because the endothelial surface in medulla and cortex is similar. These results suggest that prostacyclin could have an important influence on renal function. The different capacity of renal medulla and cortex in generation of prostacyclin could be a very important point for understanding physiology and pathophysiology of kidney function.     

Respiratory modulation of the cutaneous somatosympathetic reflex in normotensive (WKY) and in spontaneously hypertensive rats (SHR): species and strain-dependent patterns

In 6 normotensive Wistar-Kyoto (WKY) and 6 spontaneously hypertensive rats (SHRs) anesthetized with urethane and chloralose, paralyzed, artificially ventilated, vagotomized with carotid sinus nerves bilaterally cut, somatosympathetic reflex discharges were recorded in cervical and renal nerves by stimulating group II and III cutaneous afferents in the sural nerve. Only a long-circuited, late supraspinal component reflex discharge could be elicited. After averaging the responses evoked by random stimulation, the latency of the reflex discharge was significantly longer in the renal than in the cervical sympathetic nerve, equally in the WKY rat and in SHR. In WKY rats the peak of sympathetic discharge corresponded to early expiration, whereas in SHRs--to late inspiratory phase. The duration of the reflex discharge elicited in inspiration was greater in SHR than in WKY rats. In WKY rats stimuli applied during phrenic discharge produced a reflex response of longer latency and of reduced amplitude than those applied in expiration. In SHRs the latency of the reflex response in the sympathetic cervical nerve was shorter during inspiration than in expiratory phase. The timing of the sympathetic reflex responsiveness within respiratory cycle in SHR and in WKY rats corresponded to strain-dependent opposite respiratory synchronization pattern of the spontaneous sympathetic activity characterizing each strain. No respiratory modulation of the somatosympathetic reflex was observed in the renal nerve of SHR. It is concluded that both spontaneous and evoked sympathetic activity is synchronized differently in SHR and in WKY rats and this difference is both species- and strain-dependent.     

Metabolic damage to the myocardium in normotensive and hypertensive rats (morphometric analysis)

Morphological changes of myocardium were demonstrated in normotensive Wistar rats and in rats with inherited stress-induced arterial hypertension 1, 7 and 30 days following adrenaline induced damage. In acute period contracture damage to cardiomyocytes was more pronounced in Wistar rats. Death of the fraction of cardiomyocytes is compensated by hypertrophy of the surviving cells already by d 7. In hypertensive rats' hypertrophied myocardium on d 1 microcirculatory bed is more impaired, while regenerative processes in cardiomyocytes are delayed and defective, which leads to dystrophy and degeneration by the end of the experiment. It is concluded that the course and prognosis of myocardial metabolic injury is determined by its initial state and potential compensatory resources.     

Biochemical and functional changes after immunization of rats with angiotensin II

Bulletin of Experimental Biology and Medicine -     

Influence of age on position, shape and size of the carotid bodies in spontaneously hypertensive (SHR) and normotensive (NCR) rats

In normotensive Wistar rats (NCR) and spontaneously hypertensive rats (SHR) aging 3-6 d and 5-6, 15-20, 30-40 and 50-70 weeks respectively, position, shape and size of the carotid bodies were studied using ligh-microscopic methods. The anatomical position of the carotid bodies in the SHR was found to be less variable than in the NCR. In the hypertensive animals the glomera carotici were usually situated near the internal carotid artery. The carotid bodies of the NCR were of a more round-oval shape. In all age-groups the carotid bodies were compact and clearly demarked corpuscules. But also outside the principal mass of the glomera carotici small groups of type I cells were found in the surrounding nervous tissue or they appeared as miniglomera or periadventitial type I cells, respectively. These small groups of type I cells were predominantly provable in the 5-6 weeks old animals and more frequently in the NCR than in the SHR. The absolute carotid body volumes increased from birth up to an age of 30-40 weeks, whereas the relative carotid body volume, i.e. when related to the same body mass, became much smaller from birth up to an age of 15-20 weeks in both the normotensive and hypertensive animals. Except for the 5-6 weeks old group the SHR showed significantly greater carotid bodies when compared with the age-matched normotensive rats. In the course of aging in both strains of animals a stronger and more clearly developed interstitial fibrosis of the specific tissue of the carotid bodies occurred.     

The hemodynamic effect of bilateral carotid artery ligation and the morphometry of the main communicating circuit in normotensive and spontaneously hypertensive rats

After reducing the number of patent conduit arteries to the brain by bilateral ligation of the carotid artery, the percentage decrease in blood pressure from the aorta to the internal carotid artery distal to the ligation was larger in spontaneously hypertensive rats than in normotensive rats. The pressure drop corresponded to the degree of hypertension as well as to morphometrically determined structural arterial alteration in the main communicating circuit, i.e. larger media to internal radius ratio and smaller internal radius in the posterior communicating arteries, the proximal part of the posterior cerebral arteries, the basilar artery and the vertebral arteries. The discrepancy between the sum of the luminal cross sectional areas of the communicating circuit and the luminal areas of the ligated conduit arteries was larger in the hypertensive than in the normotensive rats. It is to be expected that occlusion of conduit arteries to the brain will have a larger impact on the cerebral arterial perfusion pressure head in the presence of such hypertensive structural alterations known to increase flow resistance.     

Specific desensitization (tachyphylaxis) of the guinea pig ileum to angiotensin II.

Tachyphylaxis to [Ile5]angiotensin II (angiotensin) in the isolated guinea pig ileum was found to be more severe when the Ca2+ concentration or the temperature of the medium were lowered, or when glucose was absent. Incubation with indomethacin or prostaglandin E2 did not affect the onset of tachyphylaxis or recovery from the tachyphylactic state. The angiotensin dose-response curves of tachyphylactic organs were shifted to the right, and the maximum responses were depressed in proportion to the conditioning doses of the hormone. The recovery from tachyphylaxis followed zero-order kinetics and was not affected by Ca2+ concentration or pH. The temperature dependence of the rate of recovery yielded a value of 14.6 kcal/mol for the activation energy in the physiological temperature range. It is concluded that tachyphylaxis results from the tight binding of angiotensin to superficial calcium-binding sites in the smooth muscle cell membrane. Recovery from tachyphylaxis appears to involve displacement of angiotensin by calcium in a process that is dependent on active transport.     

Role of angiotensin II type 1 (AT1) and type 2 (AT2) receptors in airway reactivity and inflammation in an allergic mouse model of asthma

Objective: Angiotensin II (Ang II) exerts its effects through two G-protein coupled receptors: angiotensin II type 1 receptors (AT1) and type 2 receptors (AT2). Both these receptor subtypes are poorly understood in asthma. In this study, we investigated effects of AT1 receptor antagonist losartan, novel AT2 receptor agonist novokinin and AT2 receptor antagonist PD 123319 in a mouse model of asthma.

Methods: Mice were divided into control (CON) and allergen sensitized (SEN) groups. SEN was sensitized with ovalbumin (OVA) on days 1 and 6 (30?μg; i.p.), followed by 5% OVA aerosol challenge (days 11–13). Treatments included (a) losartan (SEN?+?LOS; 20?mg/kg i.p., day 14), (b) novokinin (SEN?+?NOV; 0.3?mg/kg i.p., day 14), and (c) PD 123319 (SEN?+?PD; 5?mg/kg i.p., day 14). Experiments for airway responsiveness, bronchoalveolar lavage, and tracheal ring reactivity using isolated organ bath were performed.

Results: Airway responsiveness to methacholine (MCh) (48?mg/mL) was significantly higher in SEN (563.71?±?40% vs. 294.3?±?123.84 in CON). This response was potentiated in SEN?+?PD group (757?±?30%; p?<?.05 compared to SEN). SEN?+?LOS (247.61?±?86.85%) and SEN?+?NOV (352?±?11%) had significantly lower response compared to SEN. SEN?+?LOS (26.22?±?0.29%) and SEN?+?NOV (46.20?±?0.76%) treatment significantly (p?<?.001) attenuated total cell count and eosinophils compared to SEN group (69.38?±?1.5%), while SEN?+?PD (73.04?±?0.69%) had highest number of eosinophils. Tracheal response to MCh was significantly higher in SEN group compared to controls, and this response was significantly lowered with the losartan and novokinin treatments.

Conclusions: These data suggest that AT1 and AT2 receptors have opposite effects in modulating airway hyperresponsiveness and inflammation in asthma.