Mitochondrial cytochrome redox states and respiration in acute pulmonary oxygen sensing.

Hypoxic pulmonary vasoconstriction (HPV) is an essential mechanism to optimise lung gas exchange. We aimed to decipher the proposed oxygen sensing mechanism of mitochondria in HPV. Cytochrome redox state was assessed by remission spectrophotometry in intact lungs and isolated pulmonary artery smooth muscle cells (PASMC). Mitochondrial respiration was quantified by high-resolution respirometry. Alterations were compared with HPV and hypoxia-induced functional and molecular readouts on the cellular level. Aortic and renal arterial smooth muscle cells (ASMC and RASMC, respectively) served as controls. The hypoxia-induced decrease of mitochondrial respiration paralleled HPV in isolated lungs. In PASMC, reduction of respiration and mitochondrial cytochrome c and aa3 (complex IV), but not of cytochrome b (complex III) matched an increase in matrix superoxide levels as well as mitochondrial membrane hyperpolarisation with subsequent cytosolic calcium increase. In contrast to PASMC, RASMC displayed a lower decrease in respiration and no rise in superoxide, membrane potential or intracellular calcium. Pharmacological inhibition of mitochondria revealed analogous kinetics of cytochrome redox state and strength of HPV. Our data suggest inhibition of complex IV as an essential step in mitochondrial oxygen sensing of HPV. Concomitantly, increased superoxide release from complex III and mitochondrial membrane hyperpolarisation may initiate the cytosolic calcium increase underlying HPV.

Cardiovascular and renal effects of systemic hypoxia in chronically instrumented conscious WKY and SHR rats.

The effects of systemic hypoxia upon cardiovascular and renal function in normotensive Wistar-Kyoto (WKY) and spontaneously hypertensive rats (SHR) are controversial. We examined the effects of systemic normobaric hypoxia (12.5% O2 in N2 for 4 hours) on arterial blood gases (pO2, pCO2, pH), mean arterial pressure (MAP), heart rate (HR), effective renal blood flow (ERBF), glomerular filtration rate (GFR), urine flow (UMV) and renal sodium excretion (U Na V) in conscious unilaterally nephrectomized WKY (n = 12) and SHR (n = 14) chronically instrumented with an arterial, venous and ureter cannula. In WKY hypoxia caused a reduction in arterial pO2 and pCO2 but no change in MAP and HR. In SHR hypoxia induced similar reductions in arterial blood gases, a small decrease in MAP and no change in HR. In both strains hypoxia caused significant increases in ERBF, GFR and U Na V, but insignificant changes in UMV. The hypoxia-induced natriuresis developed 90-120 min after starting the hypoxia. These data indicate that a 4-hour lasting hypoxia has profound effects on sodium excretion in conscious WKY as well as SHR. Systemic hypoxia did not cause significant changes in arterial blood pressure in both rat strains.

Long term increases in coronary arterial conductance during five day infusion of low dose nicorandil.

OBJECTIVE: The aim was to test the effects of nicorandil on coronary arterial conductance and on a possible development of tolerance or cross tolerance with glyceryl trinitrate during a 5 d continuous intravenous infusion of this hybrid molecule (consisting of a combination of potassium channel activation and simultaneous nitro-ester induced soluble guanylyl-cyclase activation). METHODS: Continuous intravenous infusions of nicorandil at 2.5 micrograms.kg-1.min-1 and 10 micrograms.kg-1.min-1 into conscious chronically instrumented dogs were carried out for 5 d using a special portable infusion system. Employing additional short term infusions, dose-response curves were obtained by giving nicorandil or glyceryl trinitrate at increasing dosages both in the preinfusion control state and 4 h after terminating the nicorandil infusion. RESULTS: The 5 d infusion of 2.5 or 10.0 micrograms.kg-1.min-1 nicorandil resulted in a significant increase in large coronary artery diameter by 4.21 (SEM 0.14)% or 9.20(0.28)%, respectively. At the lower dose no significant tolerance or cross tolerance with glyceryl trinitrate was observed. However, at the higher dose there was a shift of the dose-response curve of both nicorandil and glyceryl trinitrate to the right, indicating some tolerance. The smaller dose did not induce hypotension or reflex increase in heart rate, whereas the larger resulted in a 42(2.5)% increase in heart rate. CONCLUSIONS: A dose regimen of 2.5 micrograms.kg-1.min-1 continuously administered for 5 d is capable of inducing a significant increase in coronary arterial conductance which was well maintained over the whole infusion period. Thus nicorandil can exert a selective large coronary artery dilatation and may bring about a well maintained increase in epicardial coronary conductance, especially when applied as a low dose slow release preparation which circumvents hypotension and increase in heart rate.

Reduced nitric oxide formation causes coronary vasoconstriction and impaired dilator responses to endogenous agonists and hypoxia in dogs.

We investigated the relative contribution of basal and agonist stimulated EDRF/NO release to the adjustment of coronary tone and myocardial perfusion in conscious dogs by inhibiting coronary endothelial NO formation with NG-nitro-L-arginine methyl ester (L-NAME). Chronically instrumented conscious dogs (n = 9) were prepared for measurement of mean arterial blood pressure (MAP), heart rate (HR), coronary blood flow (CF) and diameter of the left circumflex (CDLC) and left anterior descending (CDLAD) coronary artery, respectively. Intracoronary infusions of L-NAME (30.3 mM; 0.25 ml x min-1) caused significant increases in MAP and decreases in HR. CDLC decreased by 3.8% from 3.01 +/- 0.04 to 2.90 +/- 0.04 mm and CF decreases by 30% from 12.9 +/- 0.2 to 9.1 +/- 0.2 (aU). Peak reactive hyperemia (CFmax) evoked by 20-s-lasting occlusions of the left circumflex coronary artery decreased from 29.9 +/- 0.8 to 25.8 +/- 1.0 aU and maximal flow-dependent coronary dilation were reduced from 2.04 +/- 0.08 to 0.91 +/- 0.12% after inhibition of NO-synthesis. Intracoronary infusions of acetylcholine (ACh), adenosine (Ado), bradykinin (Bk), and papaverine (Pap) caused dose-dependent increases in CDLC and CF. Infusion of L-NAME nearly abolished the dilator effect of Ado on CDLC and reduced those to ACh, Bk and Pap. Increases in CF to ACh, Ado and Bk but not to Pap were reduced by L-NAME. Subsequent intracoronary infusions of L-arginine (303 mM; 0.25 ml x min-1) reduced L-NAME-induced CF-changes partly, but did not reverse coronary constriction. These results suggest that inhibition of the continuous release of nitric oxide markedly reduces myocardial perfusion in vivo.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of long-term nicorandil application on coronary arteries in conscious dogs.

Nicorandil acting as both nitrovasodilator and K(+)-channel opener was analyzed with regard to its dilator activity in large coronary arteries. In addition, it was tested for potential development of tolerance in six chronically instrumented conscious dogs that received a 5-day continuous i.v. infusion. Increasing dosages of nicorandil (3, 10, and 30 micrograms.kg-1.min-1) caused dose-dependent strong increases in left circumflex coronary artery diameter (1.3 +/- 0.4%, 5.3 +/- 2.2%, and 8.4 +/- 2.8% above control, respectively). However, 100 micrograms.kg-1.min-1 nicorandil produced substantial hypotension, reflex tachycardia, and reduction of the dilator response in large coronary arteries. During long-term nicorandil administration (10 micrograms.kg-1.min-1 i.v. for 5 days), the diameter of the left circumflex coronary artery was increased by 8.8 +/- 2.5%. This was accompanied by a decrease in mean arterial pressure of 13.3 +/- 6.4% and an increase in heart rate by 41.5 +/- 21.0% compared with controls. On the fifth day of continuous nicorandil infusion, dose-response relations for both nicorandil- and nitroglycerin-induced epicardial artery dilations were shifted to 3.5-fold higher doses. We conclude that nicorandil dilates large coronary arteries in dogs, long-term nicorandil administration does not cause a development of tolerance, long-term nicorandil administration is not associated with the development of cross-tolerance to nitroglycerin, and the small shift of the dose-response relations is considered to reflect a hemodynamic adaptation process due to long-term nicorandil exposure.

The aortic bodies of spontaneously hypertensive (SHR) and normotensive rats--a study concerning location and size.

The aortic bodies, including the right and left subclavian bodies and the superior aorticopulmonary bodies, were examined in inbred normotensive control rats (NCR) of the Wistar strain and in spontaneously hypertensive rats (SHR) of the OKAMOTO-AOKI strain. Paraganglia were found in all rats of either group. They were located near to the left common carotid artery and less frequently between the branching right subclavian and right common carotid artery. Superior aorticopulmonary bodies were rarely seen. No significant differences were found regarding the volume of individual aortic bodies when comparing these paraganglia in NCR and SHR. However, aortic bodies are more numerous in SHR and therefore the total volume of aortic body tissue per rat is significantly larger in this strain. There was good correlation between the total volume of aortic bodies and the total volume of carotid bodies in both strains of rats studied. These findings indicate, that the paraganglionic system as a whole is enlarged in SHR. This enlargement probably is caused genetically and not a result of increased blood pressure.

Hypoxic modulation of systolic blood pressure and urinary sodium excretion in spontaneously hypertensive rats after carotid body denervation.

To explore the role of arterial chemoreceptors, the effect of hypobaric hypoxia on urinary sodium excretion and systolic blood pressure was investigated in conscious spontaneously hypertensive rats (SHR) with carotid body denervation (CBD) or after sham-operation (SO). Denervation of the carotid bodies was performed by section of the carotid sinus nerves. Exposure to hypobaric hypoxia equivalent to high altitude of 4000 m led to a more pronounced decrease in systolic blood pressure in CBD-rats than in SO-rats. The pattern of urinary sodium excretion observed on the first two days of hypoxia in both groups was not affected by the chemodenervation. It is being suggested that arterial chemoreceptors do not play a critical role in blood pressure and natriuretic responses to hypobaric hypoxia in conscious SHR.

Effect of hypobaric hypoxia and almitrine on voluntary salt and water intake in carotid body denervated spontaneously hypertensive rats.

The effect of moderate hypobaric hypoxia and almitrine bismesylate (almitrine) on salt and water intake was investigated in carotid body denervated (CBD) and sham-operated (SO) spontaneously hypertensive rats (SHR). The animals were kept singly in metabolic cages and given free access to food, water and a 2.5% NaCl-solution. Oral administration of almitrine and exposure to hypobaric hypoxia for five days evoked a suppression of voluntary salt intake in SO-SHR, but not in CBD-SHR. Exposure of SO and CBD-SHR to hypobaric hypoxia resulted in a significant decrease in water intake in animals of both groups on the first day of hypoxia. Stimulation of the arterial chemoreceptors by almitrine induced no change in water intake similar to that evoked by hypobaric hypoxia. These results prove that stimulation of the arterial chemoreceptors has a direct effect on salt appetite but not on water intake in SHR.

The paraganglia within the carotid bifurcation regions of young and old spontaneously hypertensive rats (SHR) after exposure to chronic hypobaric hypoxia. I. The carotid bodies.

Carotid body volumes and the histological appearance of these chemoreceptors were studied using light microscopic methods in 10 groups of spontaneously hypertensive rats (SHR). The aim of this study was to clarify the influence of chronic hypobaric hypoxia on the carotid bodies of SHR depending on the age of the rats, on the duration of exposure to hypoxia, and on different salt intake, respectively different blood pressure. We found that: 1. The carotid bodies of chronically hypoxic SHR are enlarged. 2. The degree of carotid body enlargement is dependent on the duration of exposure to hypoxia. 3. In old SHR the increase of carotid body volume was smaller than in young SHR. 4. Old chronically hypoxic SHR exhibited more distinct vascular changes in the carotid bodies than age-matched normoxic controls as well as younger chronically hypoxic and normoxic SHR. 5. The influence of different levels of systemic arterial blood pressure on the carotid body volumes was rather small compared with the effects of chronic hypobaric hypoxia.

Electron microscopic results on the ventral prostate of the rat after CdCl2 administration. A contribution towards etiology of the cancer of the prostate.

The prostate epithelium of rats which received repeated cadmium chloride (CdCl2) injections showed a gradual disruption of structural differentiation. Electron microscopy studies revealed severe changes in the ultrastructure affecting all epithelial cell organelles, particularly the nuclei, rough endoplasmatic reticulum, the golgi apparatus, and mitochondria. The cells infiltrating the stroma contained secretory vacuoles and their nuclear evaginations on the invasion front showed similarities to ultrastructural pathological changes in man. Examinations of the ventral prostate following oral CdCl2 administration revealed changes ranging in severity up to dysplasia, but there was no evidence of carcinoma.

The carotid bodies of spontaneously hypertensive rats (SHR) after long-term stimulation by almitrine bismesylate.

The influence of daily oral application of 1.0 mg/kg almitrine bismesylate given from the 17th to the 30th week of age on the carotid bodies of male spontaneously hypertensive rats (SHR) was studied. Neither an enlargement nor histological changes of the carotid bodies were found. The results are compared with findings obtained after exposure of SHR to long-term hypobaric hypoxia and discussed.

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.

The carotid bodies of renal hypertensive rats.

The carotid bodies of renal hypertensive rats (one kidney wrap model) were studied by light-microscopic and morphometric methods. Rats with established hypertension showed massive intraglomic vascular alterations, such as exudation of plasma, subendothelial fibrinoid deposits and fibrinoid necroses of the intima and media. Additionally a granuloma-like perivascular proliferation of fibroblasts and histiocytes was seen. The total carotid body volume was enlarged but the volume of the specific glomic tissue was reduced in comparison with normotensive controls. In rats with borderline hypertension similar pathological changes were found but in a more reduced extension. Additionally in these rats some intraglomic vessels showed an accumulation of acid mucopolysaccharides and an hyperplasia of mediocytes. Rats with such vessel alterations also exhibited a small enlargement of specific glomic tissue. In general the pathological changes of the carotid bodies in renal hypertensive rats are different in comparison with those in the glomera carotici of rats with spontaneous hypertension (SHR, GH rats). This study suggests that an elevated blood pressure does not solely cause an increment of the specific chemoreceptive tissue mass of the carotid bodies.

Effect of almitrine on renal sodium excretion in chemoreceptor denervated spontaneously hypertensive rats.

The effect of almitrine on urinary sodium excretion was investigated in conscious carotid body-, sino-aortic- and sham-denervated SHR. The animals were kept singly in metabolic cages and had free access to food and tap water. Oral application of almitrine (0.5 mg/kg bwt) during five days induced a twofold natriuresis in sham-operated rats. The first natriuretic response on the fourth day of almitrine treatment was observed in animals of all groups indicating that this effect is not chemoreceptor mediated. The second natriuresis seen on the sixth day of the post-treatment period in both sino-aortic and sham-operated SHR but not in the carotid-body denervated rats does not permit clear conclusions to be drawn. We tend to assume that the natriuretic action of almitrine is not chemoreceptor mediated in conscious SHR.

A comparison of carotid body volumes in normotensive Wistar rats (NWR), Wistar Kyoto rats (WKY) and spontaneously hypertensive rats (SHR).

The carotid body volumes of male spontaneously hypertensive rats (SHR), Wistar Kyoto rats (WKY) and random-bred normotensive Wistar rats (NWR) were compared at the age of 16-18 weeks. SHR exhibited significantly greater absolute and relative carotid body volumes (CBV) than WKY or NWR. Furthermore, the absolute and relative CBV in WKY was also significantly bigger than in NWR. The same differences were found regarding the mean arterial blood pressure. The mean arterial blood pressure was significantly correlated with the logarithmic values of both the absolute and the relative CBV in SHR, WKY and NWR. These findings were compared with the results of other hypertensive rat models. It can be concluded that in hypertensive rats the CBV is likely to be dependent on the strain studied and independent of the blood pressure level or the expression of intraglomic vascular alterations.

The carotid bodies of spontaneously hypertensive rats after long-term antihypertensive treatment with propranolol.

The influence of a chronic blood pressure lowering on carotid body morphology and volume was studied in spontaneously hypertensive rats (SHR). Oral propranolol, a beta-adrenergic blocking agent, was administered beginning 3 weeks after conception up to 18 weeks of the litters. At the end of the experiment the blood pressure was significantly lower in the treated animals. These rats exhibited fewer vascular alterations in their carotid bodies. The carotid body volumes and the relationship of glomic cells, the blood vessels including endothelial cells, and the connective tissue in the carotid bodies did not differ between treated and non-treated rats. It can be concluded that long-term blood pressure lowering by propranolol in SHR does not influence carotid body volume increase.

Blood pressure, heart rate and arterial blood gas reactions to acute hypoxia in carotid body denervated spontaneously hypertensive rats.

The role of the peripheral arterial chemoreceptors in the reflex control of respiration and the cardiovascular systems was studied in spontaneously hypertensive rats (SHR). In carotid body denervated and in sham-operated control rats mean arterial blood pressure, heart rate, respiratory rate and arterial blood gases were measured under normoxic conditions and in acute normobaric hypoxia. Under normoxia the carotid body denervated SHR differ from the sham-operated ones only in significantly lowered arterial pO2 and pH and in significantly increased pCO2 values. The carotid body denervated SHR react to acute hypoxia with a significantly smaller increase in respiratory rate, a more pronounced fall in the arterial pO2 and a greater decrease in mean arterial blood pressure than the sham-operated control rats. Our results suggest that carotid body chemoreceptors in SHR are of great importance in regulating respiration but of secondary consequence regarding the reflex control of the cardiovascular system.

Hypoxia-induced regression of adaptive structural microvessel reactions caused by long-term contraction influences in spontaneously hypertensive rats (SHR).

Chronic effects of hypobaric hypoxia (hb.h.) on the microcirculatory system (m.s.) of skeletal muscle were investigated. A new histomorphometric method was applied to detect the adaptive structural reactions of wall cells to long term changes in contraction performance. Seventeen SHR were exposed to hb.h. from 5 to 18 or 17 to 30 weeks of life, respectively. For controls 19 SHR and 25 normotensive Wistar rats were kept at sea level. The findings document long-term actions of vasorelaxation factors in hb.h. and the ability of the latter to antagonize the intensified vasocontraction factors in SHR. Depending on the stage of hypertension, there are different preferential sides for the actions of both these factors within the various districts of the m.s.