摘要:

The serum protein, opsomucoid has been shown to be essential for the maintenance of normal capillary permeability in several different organs, including the kidney. Thus, the clearance of albumin was found to be almost fivefold higher in the absence of orosomucoid in a previous study on isolated rat kidneys, perfused with either of two commercially available human albumin solutions of similar composition, but differing in their content of orosomucoid (0.21 g 1‐‐1vs.<0.005 g 1‐‐1), The following experiments were performed in order to verify the hypothesis that this effect on glomerular permselectivity was due to orosomucoidper seand not to other ingredients in the two solutions. Both kidneys of 12 rats were isolated and perfused with identical albumin solutions without orosomucoid, but with the addition of purified orosomucoid (0.25 g 1‐‐1) to one of the kidneys. No significant differences in vascular resistance, urine flow or glomerular filtration rate (GFR), which was found to be 27 ± 2 ml min‐1100 g‐1, were observed between the two groups of kidneys. The fractional clearance of albumin (θ) was initially similar for both kidneys (0.0022 ± 0.0002). In the absence of orosomucoid, θ gradually increased to 0.0076 ± 0.0013 after 1 h of perfusion compared to 0.0040 ± 0.0006 for the kidneys with orosomucoid added to the perfusate (P<0.001,n= 12). We conclude that the plasma glycoprotein orosomucoid indeed plays an important role in regulating the dynamic properties of the glomerular capillary wall by reducing the permeability towards macromole

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1993.tb09466.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Phenylephrine induces endothelium‐independent rhythmic contractions in ryanodinetreated rabbit mesenteric arteries. To elucidate the ionic mechanism of this rhythmic behaviour, rabbit mesenteric arterial rings were suspended in an organ chamber for isometric tension studies. Yohimbine, propranolol, and atropine had no effect on these contractions, minimizing the possibility that transmitter release from nerve terminals was involved. Additionally, the oscillatory contractions were not altered by diphenhydramine, cimetidine, and indomethacin, thus ruling out the involvement of histamine and prostaglandins. This oscillatory response was completely abolished after the removal of extracellular Ca 2+, as well as after Ca 2+ channel blockade by diltiazem or nifedipine. Sparteine and quinidine, Ca 2+‐activated K+ channel antagonists, also abolished the oscillation. In contrast, tetraethylammonium and 3,4‐diaminopyridine, voltage‐dependent K+ channel antagonists, augmented the response. Glibenclamide, an antagonist of the ATP‐sensitive K+ channel, had no effect on the rhythmic contractions. These results suggest that the rhythmic contractions observed in rabbit mesenteric arteries after ryanodine treatment were caused by the movement of Ca 2+ and K+ across the plasmalemma via the voltage‐dependent Ca 2+ channel and the Ca 2+‐activated K+ channel,

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1993.tb09467.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

The roles of different mediators in the sympathetic regulation of the pig and dog spleens were investigated using a preparation with intact vascular perfusionin vivo. Sympathetic nerve stimulation caused overflow of neuropeptide Y‐like immunoreactivity (NPY‐LI) and noradrenaline (NA), arterial vasoconstriction, increase in venous blood flow and haematocrit. The dog spleen responded to single impulse stimulation, whereas more prolonged stimulation was required to elicit vascular responses in the pig spleen. Furthermore, the maximal splenic capacitance response was about 10 times larger in the dog than in the pig. After depletion of neuronal NA content by reserpine combined with preganglionic denervation, about 70% of the splenic arterial vasoconstrictor responses in the dog and pig still remained at 5 Hz stimulation. Fifty per cent of the capacitance response evoked by nerve stimulation still remained in the pig while in the dog spleen the capacitance response was virtually abolished after reserpine. The stimulation‐evoked overflow of NPY‐LI in pig spleen was increased several fold after reserpine treatment as compared to controls reaching levels in the venous effluent where exogenous NPY evokes vasoconstriction. In the dog spleen, overflow of NPY‐LI was only observed after reserpine. Administration of NA caused arterial vasoconstriction with an initial increase in venous blood flow while NPY mainly reduced arterial blood flow.It is concluded that NA is involved in both the splenic arterial vasoconstriction and the capacitance responses while a non‐adrenergic splenic vasoconstriction at least in the pig may be medi

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1993.tb09468.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

In order to elucidate a possible influence of the sympathetic nervous system on afferent nerve function, rat mandibular incisors were electrically stimulated and blood flow changes monitored in the incisor pulp of untreated and sympathectomized animals by a laser Doppler flowmeter. Monopolar electrical stimulation of the tooth (200 μA, 5 ms, 40 Hz, 1 s) in normal animals resulted in a transient reduction in pulpal blood flow (PBF) (16%, reduction,n= 10) followed by a small but long‐lasting increase (11% increase). After administration of phenoxybenzamine or phentolamine (3 mg kg‐1, i.v.) the initial dip in PRF was reduced by 59% (P<0.001) while the subsequent increase was enhanced by 185% (P<0.001). Similarly, infusion of prazosin (50μg kg‐1, i.v.) and idazoxan (0.5 mg kg‐1i.v.) significantly enhanced the increase in PBF by 118 and by 79%, respectively. In chronically sympathectomized animals the increase in PBF was 250% larger than that seen in untreated animals (P<0.001). This increase in PBF was not further enhanced after α‐adrenergic blockade. Acute resection of the superior cervical sympathetic ganglion, also resulted in some enhancement (by 56%) of the stimulation‐induced increase in PBF (P<0.01,n =6). The increase in PBF was unaffected by infusion of timolol (150 μgkg‐1) and atropine (1 mg kg‐1) but was totally abolished by intravenous pre‐treatment with capsaicin (1–3 mg kg‐1). The present results suggest that activation of sympathetic nerves exerts inhibitory effects on the afferent nerve‐induced vasodilation in the rat incisor pulp unrelated to s

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1993.tb09469.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

In order to obtain a functional estimate of the diffusional capacity of the myocardial capillary bed, the permeability surface area product (PS) for Cr‐EDTA (mol. wt = 341) and cyanocobalamine (vitamin B12, mol. wt = 135) was determined in spontaneously beating Langendorff‐perfused rat hearts over a wide range of coronary flow rates (700–3000 ml min‐1100 g‐l). PS was determined by a single injection, colorimetric indicator dilution technique, allowing multiple, rapid and accurate determinations to be made in the same heart. During maximal vasodilation with nitroprusside Na PS averaged 535 ± 33 and 220 ± 22 ml min‐1100 g‐1for Cr‐EDTA and vitamin B12respectively at the highest flow (2917 ±74 ml min‐1100 g‐1). The vasculature of the heart was found to be highly hererogeneous, since PS increased with flow and there were marked variations of extraction over transit times. A functional estimate of ‘equivalent pore radius’ was obtained from the ratio PSCr.EDTA/PSB12, which was 2.61 ± 0.15 demonstratiag a marked restriction to diffusion corresponding to a pore radius of 51 (41–75) Å. This value is similar to that from skeletal muscle determined by the same method while PS‐values are 40–45 times higher in the heart (Haraldsson&Rippe 1986). Taken together with morphological estimations of capillary surface area and endothelial path depth, these data indicate a 3‐fold increase in the density of pores available for diffusion in the myo

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1993.tb09470.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

The present study investigated how variations in coronary vascular resistance and metabolic demand affected myocardial capillary diffusion capacity. Hearts from Wistar rats were perfused with Krebs‐Henseleit‐albumin buffer in a Langendorff preparation, where heart rate (HR), contractility (dP/dtmax) and myocardial oxygen consumption (MVO2) were recorded continuously. Myocardial capillary diffusion capacity was measured as the permeability surface area product (PS) for Cr‐EDTA and vitamin B12by the single injection colorimetric indicator dilution method. After base‐line recordings without drugs, angiotensin II + arginine‐vasopressin was infused, which increased coronary vascular resistance by 90%, stimulated HR by 11%, decreased dP/dtmaxby 21% and reduced MVO2by 4%. PSCr‐EDTAand PSB12, decreased by 24 and 27%, respectively, leaving the ratio PSCr‐EDTA/PSB12unchanged indicating unaltered capillary permeability. Moreover, the reductions in MVO2and PS correlated significantly. During vasodilation: (1) nitroprusside‐NA stimulated HR by 7% and decreased dP/dtmaxby 14%; (2) adenosine reduced dP/dtmaxby 37% and decreased MVO2by 9%; and (3) isoproterenol increased HR, dP/dtmaxand MVO2by 53, 76 and 9%, respectively. However, all three vasodilators reduced PSCr‐EDTAand PSB12in parallel by 7–25% leaving PSCr‐EDTA/PSB12unchanged.Thus, maximal estimated diffusion capacities were obtained during spontaneous coronary vascular tone, most likely reflecting maximal capillary recruitment in the Krebs‐Henseleit‐albumin perfused heart. The derecruiting effects of the vasoconstrictors were partly overridden by metabolic factors, while the reductions of PS after vasodilation more likely were due to increased heter

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1993.tb09471.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

The effect of changes in preload on regional myocardial motion in acute ischaemia was examined by miniature ultrasonic gauges after left anterior descending coronary artery occlusion in eight open chest dogs with the pericardium preserved. Left ventricular end‐diastolic pressure was varied by blood withdrawal and infusion. When preload changed, isovolumetric shortening in the non‐ischaemic region was inversely related to that in the ischaemic region. When preload decreased, stroke volume decreased and was accompanied by a decrease in end‐diastolic length and ejection shortening in the non‐ischaemic region together with an increase in isovolumetric bulging in the ischaemic region. When preload increased, these variables changed in opposite directions. These results indicate that in acute ischaemia: (1) changes in isovolumetric shortening in the non‐ischaemic and ischaemic regions were related with each other when the level of volume expansion varied, and suggest that; (2) stroke volume is affected by end‐diastolic length, ejection shortening in the non‐ischaemic region and isovolumetric bulging in the is

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1993.tb09472.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

The effects of an oral glucose load of 75 g on the local forearm and whole‐body energy thermogenesis were measured in normal subjects during the 4 h after the glucose intake. Simultaneous assessment of substrate metabolism in the forearm was performed.Energy expenditure (EE) increased after the glucose load and had not returned to baseline level at the end of the experiment. Whole‐body respiratory quotient (RQ) was, on average, 0.80 (SD 0.05) in the baseline condition and increased to a maximum of 0.91 (0.03) and then decreased to baseline level at the end of the experiment. The local forearm oxygen uptake increased 30 min after the glucose intake and remained elevated during the rest of the experiment. The carbon dioxide output from the forearm did not increase before 90 min after the glucose load. Consequently the local forearm RQ decreased significantly from a baseline value of 0.86 (0.17) to 0.63 (0.17) 30 min after the glucose load (P<0.05). Ninety min after the glucose load RQ increased to a maximum level at 0.95 (0.22) and decreased then gradually to baseline level.The experiments emphasize several methodological problems in the measurement of local forearm RQ The whole‐body RQ and local forearm RQ are not significantly different in the fasting state. The finding of a decrease in local forearm RQ below 0.70 30 min after the glucose load probably indicates a non‐steady state in the carbon dioxide exchange. Thus, indirect calorimetry cannot be applied locally during short time

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1993.tb09473.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Six subjects performed isometric contraction (66% maximal force) to fatigue with the knee extensor muscles. Biopsies were taken from the quadriceps femoris muscle at rest, at fatigue and 1 min after termination of contraction. In three of the subjects recovery from contraction occurred in the presence of an intact circulation (non‐occluded, NON) to the thigh, whereas in the other three the circulation during recovery was occluded (OCC). Glycogen synthase fractional activity (GSF) decreased in all subjects from (mean±SE) 0.53 ± 0.06 at rest to 0.37 ± 0.04 at fatigue (P<0.001). In the OCC group GSF returned to the pre‐exercise value within 1 min after termination of contraction (0.59 ± 0.07 at rest vs. 0.57 ± 0.04 at 1 min post‐exercise), whereas in the NON group GSF increased to a higher extent (0.48 ± 0.09 at rest vs. 0.70 ± 0.06 at 1 min post‐exercise). The increase in GSF during the 1‐min recovery was almost three‐fold higher in the NON group (0.15 ± 0.02 vs. 0.38 ± 0.03). Cyclic AMP‐dependent protein kinase (CAMP‐PK) (assayed at 0/100 μm and 0.2/100 μm cAMP) did not change at fatigue or during recovery in either group. Glycogen synthase phosphatase (GSP) increased at fatigue by ˜ 30% (P<0.05 vs. rest). It is concluded that isometric contraction mediated inactivation of GS (i.e. phosphorylation of GS) is due to activation of a protein kinase(s) but not cAMP‐PK. The rapid activation of GS in the NON group demonstrates that a humoral factor(s), possibly insulin and/or oxygen, is re

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1993.tb09474.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Using31P magnetic resonance spectroscopy we compared skeletal muscle bioenergetics in Wistar rats made chronically anaemic by being fed a diet deficient in iron for 6 weeks with chronically iron deficient animals given a normal diet as well as 5 mg iron dextran at 2 or 7 days before experimentation. Spectra of the gastrocnemius muscle were taken at rest and during stimulation of the sciatic nerve at 2 Hz for 10 min. Relative concentrations of intracellular phosphate (Pi), phosphocreatine (PCr) and ATP were determined. Iron deficiency increased PCr breakdown and production of acid in stimulated skeletal muscle. Recovery of PCr and Pi concentrations after exercise was slow. These metabolic changes are consistent with either a reduction in supply of oxygen to the muscle cell or altered oxidative phosphorylation by the mitochondria. The latter may be mediated by defective function of iron‐containing proteins crucial in oxidative phosphorylation and this is suggested both by the observation that treatment with iron, sufficient to correct the anaemia, does not completely reverse the metabolic changes and that there is a different time course for such metabolic improvements and the observed increase in haemoglobin concentratio

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1993.tb09475.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY