Cardiac and regional haemodynamic effects of endothelin-1 in rats subjected to critical haemorrhagic hypotension.

In the present study, we examined cardiac and regional haemodynamic effects of endothelin-1 (ET-1), a potent vasoconstrictive factor, in a rat model of pressure-controlled irreversible haemorrhagic shock resulting in the death of all control animals within 30 min. Experiments were carried out in male ethylurethane-anaesthetised Wistar rats subjected to hypotension of 20-25 mmHg, which resulted in bradycardia, an extreme decrease in cardiac index (CI) and an increase in total peripheral resistance index (TPRI), with reductions in renal (RBF), hindquarters (HBF) and mesenteric blood flow (MBF). ET-1 (50, 200 pmol/kg) administered intravenously at 5 min of critical hypotension produced increases in mean arterial pressure (MAP) and heart rate (HR), which were significantly higher than those in normotensive animals, and a 100% survival at 2 h after treatment. The effects were accompanied by a rise in CI, a decrease in TPRI, with increases in RBF and HBF and persistently lowered MBF, and an increase in circulating blood volume 20 min after treatment. The cardiovascular effects of ET-1 were inhibited by the ETA receptor antagonist BQ-123 (1 mg/kg), while the ETB receptor antagonist BQ-788 (3 mg/kg) had no effect. In conclusion, ET-1 acting via ETA receptors produces reversal of haemorrhagic hypotension in rats due to the mobilisation of blood from venous reservoirs, with the improvements in cardiac function and the perfusion of peripheral tissues.

Effect of phosphoramidon on brain tissue angiogenesis in the chronic phase of vasospasm after subarachnoid hemorrhage in the rat.

BACKGROUND: Subarachnoid hemorrhage (SAH) frequently leads to prolonged cerebral vasospasm resulting in vascular pathology due to endothelial cell ischemia and neuronal hypoxia. Posthemorrhagic vasospasm can be counteracted by the administration of phosphoramidon, which blocks the endothelin converting enzyme (ECE) responsible for the conversion of big endothelin into a fully active ET1 peptide. The aim of the study was to determine the effect of chronic vasospasm after SAH on angiogenesis and the effect on this process of endothelin-1, the main causative factor in vasospasm. MATERIAL AND METHODS: Male Wistar rats were examined. Seven days after cannulation of the cisterna magna, blood was administered to induce SAH. The ECE inhibitor phosphoramidon was administered in a dose of 40 nmol in 50 microl of cerebrospinal fluid three times: 20 min before SAH, 60 min after SAH, and 24 hours after SAH. The brains were removed 48 hours later for histological evaluation. The vascular surface density was measured in cerebral hemisphere sections (at the level of the dorsal part of the hippocampus) and brainstem sections (1/2 of the pons). CONCLUSION: Increased angiogenesis was observed in the cerebral hemispheres after SAH. The administration of phosphoramidon inhibits angiogenesis in cerebral hemispheres after SAH.

Cerebral angiogenesis after subarachnoid hemorrhage (SAH) and endothelin receptor blockage with BQ-123 antagonist in rats.

The aim of the study was to determine the effect of chronic vasospasm after SAH on angiogenesis and the effect of endothelin-1, the main causative factor in vasospasm, on this process. Male Wistar rats, 220-250 g, were examined. Seven days after cannulation of the cisterna magna (CM), a 100 microl dose of non-heparinized blood was administered to induce SAH. Sham SAH (aSAH) was induced by intracisternal injection of 100 microl of artificial cerebrospinal fluid. Endothelin receptor antagonist BQ-123 in a dose of 40 nmol in 50 microl of cerebrospinal fluid was given three times: 20 min. before SAH and aSAH, 60 min and 24 hours after SAH and aSAH. The same pattern of BQ-123 administration was used in the nonSAH group. The brains were removed 48 hours later for histological evaluation. Vascular surface density was measured in cerebral hemisphere sections (at the level of the dorsal part of the hippocampus) and brain stem sections (1/2 of the pons). An increase in angiogenesis was observed after SAH, compared to control values. The administration of BQ-123, a specific endothelin receptor blocker inhibits angiogenesis in cerebral hemispheres after SAH.

Endogenous opioid peptides system in haemorrhagic shock--central cardiovascular regulation.

BACKGROUND: Haemorrhagic hypotension is accompanied by an increase in endogenous opioid system activity, however, its significance is not fully recognised. Therefore, the role of endogenous opioid peptides in the central cardiovascular regulation in haemorrhagic shock was reviewed. CONCLUSIONS: Complex central opioid mechanisms play an essential role in regulation of cardiovascular centre function in haemorrhagic hypotension since activation of mu and blockade of delta 1 opioid receptors inhibit the initiation of sympathoinhibitory phase of regulation, while activation of kappa receptors blocks the compensatory cardiovascular responses to haemorrhage. Evidences indicate that central nitrergic and glucocorticoid mechanisms are involved in endogenous opioids action.

Expression of vascular endothelial growth factor (VEGF) in rat brain after subarachnoid haemorrhage and endothelin receptor blockage with BQ-123.

Cerebral vasospasm is one of the most severe complications of subarachnoid haemorrhage (SAH), leading to pathological changes in the vessel wall itself and in the nervous tissue, due to ischaemia of endothelial cells and neurones. Amongst the known substances inducing vasospasm, the most potent spasmogenic effect is exerted by endothelin-1 (ET1). The constriction of cerebral arteries and obliteration of capillaries highly stimulates the secretion of growth factors by endothelial cells and induces compensatory formation of collateral circulation in response to brain ischaemia. Expression of vascular endothelial growth factor (VEGF), the main factor responsible for angiogenesis and vascular permeability, was found to be increased in hypoxic cells (irrespective of the cause of hypoxia) as well as in neoplastic cells in the brain. The aim of the study was to determine whether chronic vasospasm and hypoxia of endothelial cells stimulate expression of VEGF, and whether blockage of the endothelin receptor ET(A) reduces this expression. The SAH was induced experimentally in male Wistar rats and the ET(A) receptor antagonist--BQ-123 was administered into the cisterna magna. After 48 hours the brain was removed and expression of VEGF studied immunohistochemically on paraffin sections. We found that hypoxia of endothelial cells, induced by chronic vasospasm after SAH, caused increased expression of VEGF in brain vessels and neurones of the cerebral hemispheres, brain stem and cerebellum. After administration of the endothelin receptor antagonist BQ-123, no changes in VEGF expression in the brain were found.

Effect of endothelin-1 receptor antagonist BQ-123 on basilar artery diameter after subarachnoid hemorrhage (SAH) in rats.

Aim of the study was to quantify cerebral vasospasm in rats after subarachnoid hemorrhage (SAH) by morphometric examination of basilar artery and to evaluate the influence of endothelin receptor blocker BQ-123 on basilar artery constriction. The rat cisterna magna (CM) was cannulated and after 7 days SAH was developed by administration of 100 microl autologic, non-heparinized blood to the CM. The sham subarachnoid hemorrhage was developed by intracisternal administration of 100 microl of artificial cerebrospinal fluid. Endothelin receptor blocker BQ-123 was injected into the CM in a dose of 40 nmol diluted in 50 microl of cerebrospinal fluid 20 min. before SAH, and 24h and 48 h after SAH. After perfusion fixation the brains were removed from the skull and histological preparations of basilar artery were done. The internal diameter and wall thickness of basilar arteries was measured by interactive morphometric method. The most severe vasospasm was found in rats after SAH. The presence of numerous infiltrations composed of neutrophils and macrophages correlated with advanced vasospasm (index of constriction 5 times lower than in normal), suggesting the role of other factors participating in the late phase of vasospasms after SAH. Administration of BQ-123 in the late phase after SAH caused the dilatation of basilar artery. Following the administration of BQ-123 in the late phase (48 h after SAH) the basilar artery dilated, its wall became thinner, and the number of leukocyte infiltrations in the subarachnoid space decreased compared to the values after SAH alone.

Reactivity of cerebral arteries after subarachnoid hemorrhage in rats after phosphoramidon administered.

The aim of the study was to quantify cerebral vasospasm in rats after subarachnoid hemorrhage (SAH) by morphometric examination of basilar artery and to evaluate the influence of Phosphoramidon on basilar artery constriction. The rat cisterna magna (CM) was cannulated and after 7 days SAH was developed by administration of 100 microliters autologic, non-heparinized blood to the CM. The sham subarachnoid hemorrhage was developed by intracisternal administration of 100 microliters of artificial cerebrospinal fluid. After 60 min and after 24 h Phosphoramidon was injected into the CM in a dose of 40 nmol diluted in 50 microliters of cerebrospinal fluid. After perfusion, the brain was removed from the skull and histological preparations of the basilar artery were made. The internal diameter and wall thickness of basilar arteries were measured by interactive morphometric method. The most severe vasospasm was found in rats after SAH and the administration of Phosphoramidon in the late phase after SAH caused the dilatation of the basilar artery. The presence of numerous infiltrations composed of neutrophils and macrophages correlated with advanced vasospasm (index of constriction 5 times lower than normal), suggesting the role of other factors participating in the late phase of vasospasms after SAH.

Vascular endothelial growth factor (VEGF) and its effect on angiogenesis.

The article discusses the role of vascular endothelial growth factor(VEGF) in angiogenesis in embryonic development, particularly the effect of VEGF on capillary formation in response to chronic tissue ischemia and hypoxia. The sources and action of numerous angiogenic and angiostatic factors responsible for morphologic development of endothelial cells and disturbances in VEGF and FGF secretion are also presented. Increased VEGF and VEGF receptor expression enhances vascular permeability and angiogenesis, and is the cause of tissue edema as well as tumor and metastasis formation. VEGF appears to have a beneficial effect only in ischemic diseases of the heart and peripheral vessels. The article highlights the therapeutic implication of VEGF suppression in other areas of ischemia.

Influence endothelin ETA receptor antagonist--BQ-123--on changes of endothelin-1 level in plasma of rats with acute vasospasm following subarachnoid hemorrhage.

Endothelin participates in regulating the vascular tone, and it is also involved in the pathogenesis of vasospasm following subarachnoid hemorrhage (SAH). Endothelin-1 (ET-1) induced cerebral vasospasm is inhibited by ETA receptors specific antagonist-BQ-123; this protects the neurons from ischemic damage. The present study evaluates the dynamics of ET-1 concentration changes in the plasma of rats in the acute phase of vasospasm after SAH, which was induced by administering 100 microliters non-heparinized fresh autologous arterial blood into the brain cisterna magna (CM). The study also assesses the effect of blocking ETA receptors on the changes in ET-1 level. BQ-123, the specific ETA receptors antagonist, was administered to cerebrospinal fluid (CSF) through a cannula inserted into CM; the antagonist--40 nmol in 50 microliters CSF--was given 20 minutes prior to SAH. In the control group, sham SAH was induced by administering 100 microliters artificial CSF (aCSF) to CM. ET-1 concentration in the plasma of rats in the acute phase of vasospasm was assessed by radioimmunoassay 30 and 60 minutes after SAH or sham SAH. It has been showed that both SAH and sham SAH cause significant increase in the ET-1 concentration (p < 0.05) in the rat plasma after 30 minutes; the concentration returns to an initial value after following 30 minutes, which may suggest that ET-1 released binds to its receptors in the acute phase of the vasospasm. On the other hand, in the two groups of rats with blocked ETA receptors there was a significant rise in ET-1 concentration 30 minutes after SAH or sham SAH, and a still further rise was observed 60 minutes after the procedure. The rise was significantly higher in animals with SAH (p < 0.05). The dynamics of the ET-1 concentration changes observed in rats with blocked ETA receptor suggests that SAH is an ET-1 production stimulator significantly more potent than other factors assessed in the study, such as a rise in the intracranial pressure resulting from administering aCSF to CM. Blocking ETA receptors makes it impossible for the ET-1 released to bind to the receptors, which may be a factor preventing the occurrence of cerebral vasospasm following SAH.

[The role of endothelin in regulation of vascular tone in physiology and pathology]. / Rola endoteliny w regulacji napiecia scian naczyn w fizjologii i patologii.

This paper discuss importance of the endothelin, present in the plasma and other fluids, on the vascular smooth muscles in physiology and pathology. Endothelin-1 as one of the very strong vasoconstructive peptides influences the vascular tone. We discuss the competitive action of vasoconstrictors and vasodilators in promoting of vasospasm, especially in the states, where endothelial cells are injured.

Atrial natriuretic peptide secretion following subarachnoid hemorrhage in spontaneously hypertensive rats.

Atrial natriuretic peptide (ANP) is released excessively in spontaneously hypertensive rats (SHR), and vasodepression is its main effect on the blood vessels. The aim of the study was to investigate the changes in ANP secretion in the cerebral vasospasm following subarachnoid hemorrhage (SAH) in SHRs. The SAH was induced by the injection of 100 microliters of unheparinized, autologous blood into the cerebrospinal fluid (CSF), via a canule formerly inserted into the cisterna magna (CM). In the sham SAH group the SAH was imitated with 0.9% saline injection. The concentrations of ANP in the blood samples obtained in the acute and chronic stages of vasospasm were radioimmunoassayed with commercial RIA kits (Peninsula RIK 9103). It was found that both SAH and sham SAH induced a significant increase in plasma ANP in the chronic phase of vasospasm. No such changes were observed in the acute phase. This shows that the chronic cerebral vasospasm following SAH considerably enhances the ANP secretion in SHRs, probably through the increased endothelin release. These compensatory and regulatory mechanisms help prevent the development of brain oedema and the progression of vasopasm through secondary vasodilation.

Anti-aggregatory activity of PGI2 in whole blood measured by platelet counter.

Anti-aggregatory effect of PGI2 was evaluated by two methods. First, by measurement of the number of free platelets in a sample of whole citrated blood after addition of ADP, and second, by monitoring changes in light transmission induced by ADP in platelet-rich plasma. Platelet aggregation in response to ADP, as assessed by the first method, was dose-dependent, reproducible, and stable during 10-60 min storage of blood samples. EC50's for ADP were (microM): 0.7 (first method) and 2.9 (second method). IC50's for anti-aggregatory effect of PGI2-tested with 1 microM of ADP were (nM): 0.48 (first method) and 2.32 (second method), the difference suggesting higher sensitivity of the first method. Measurement by the first methods can be performed 1 min after blood collection. It is concluded that evaluation of the anti-aggregatory effect of PGI2 by monitoring the free platelet number in ADP-treated whole blood is more sensitive than the conventional turbidimetric technique since it allows detection of blood PGI2 levels more than 100 times smaller than the turbidimetric method and seems suitable for monitoring PGI2 therapy in clinical studies.

Effect of PGI2 on platelet aggregates in myocardial infarction evaluated in vitro in whole blood. The method for quantification of platelet aggregates.

PGI2 was found to increase the number of free platelets (FP) in citrated whole blood (WB) as a result of incomplete dispersion of platelet aggregates of various magnitudes. In WB from young, male volunteers the effect of PGI2 on FP number was absent immediately after blood collection, increased with time of blood storage, and was dose-dependent. In WB from 14 males with myocardial infarction (MI) effect of PGI2 on FP number was higher than in 11 male patient controls (PC). On 14th day after MI effect of PGI2 on FP in WB was reduced. It is concluded that measurement of PGI2-sensitive platelet aggregates may be of some clinical significance. However, presented results did not allow for differentiation between circulating platelet aggregates and those formed in vitro during spontaneous aggregation of platelets.

Arterial blood pressure and electric activity of aortic nerves in rabbits during hyperthermia.

The experiments were carried out on 30 rabbits with whole body heating to lethal temperatures. During the process of heating records were done of the rectal temperature, arterial blood pressure, heart rate, ECG and action potentials in the aortic nerves. It was found that heating the animals up to 41.5 degrees and to 43 degrees C increased initially slightly the arterial blood pressure but then decreased this pressure gradually. The heart rate increased during heating but decreased steeply at temperatures preceding death. The fall of the arterial blood pressure was associated with a decrease in the frequency of action potentials in the aortic nerves. The appearance of isolated action potentials within several minutes after heart arrest suggests spontaneous activity of certain baroreceptors.

Effect of stimulation of aortic nerves in rabbits under hyperthermia.

Stimulation of the aortic nerves was studies in 20 rabbit in relation to increasing body temperature. Depressive reaction was not changed within temperature range of 38--42 degrees C. This reaction was abolished when the temperature exceeded 42 degrees C, in spite of the fact that heating was discontinued and the body temperature returned to its initial value. A complete loss of the reaction or trace depressive reaction, observed when the temperature exceeded 42 degrees C, could be due to thermal inactivation of the neurons in the cardiovasomotor centre.

[Energy expenditure of workers in a copper mill]. / Wydatek energetycvzny pracowników huty miedzi.

The results of the studies of energetic expenditure at 63 different workstations in copper mill were presented. 212 determinations of energetic expenditure were performed with direct colorimetry. 11% of the workstations exhibited a high energetic expenditure and hazardous working environment conditions. The results imply the necessity to modernize the mill and improve the preventive activities within industrial health service.