ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1988.tb08427.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

The influence of renal sympathetic nerve stimulation on fluid reabsorption in the proximal tubules was studied in anaesthetized male Sprague‐Dawley rats. Direct stimulation with a frequency of 2 Hz was applied, and a modification of the split oil droplet technique was used. The fluid reabsorption was determined as the half‐time (t1/2) of the shrinking droplet. In the control situationt1/2was 30.7 ± 3.4 s. On stimulation at 2 Hz,t1/2decreased in all nine rats studied by an average of 25 ± 5%, to 22.4 ± 2.6 s (P<0.01). The decrease int1/2indicates an increased rate of proximal tubular fluid reabsorption. The results support the concept that the anatomically established adrenergic innervation of renal proximal tubules participates in the direct regulation of tubular fluid reabsorption, a role which might be important in the control of the extracellular

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1988.tb08428.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

The functional characteristics of the capillary membranes of rat kidneys were analysed in a computer‐based model utilizing previous data on the hydraulic conductivity of the membranes and transport by diffusion, hydraulic flow and ion migration of: inulin, myoglobin (negative, neutral and positive), horseradish peroxidase (negative and neutral), lactate dehydrogenase (negative, neutral and positive) and albumin. The results showed that in the peritubular capillaries the main fluid reabsorption (26.8 times 10‐8ml nephron‐1100 g body wt‐1) occurs through a set of 20 Å pores with a total pore area over pore length of 30 cm x (nephron 100 g body wt)‐1, whereas the plasma proteins enter the renal interstitium through a few 140 Å large pores with a total pore area over pore length of 7.2 times 10‐4cm and a fluid reabsorption of 1.2 times 10‐10ml nephron‐1100 g body wt‐1. The intramembranous concentration of negative fixed charges in the large pore system was estimated at 20 mM (range 15–22 mM). Since this was accompanied by a potential difference of 0.3 mV, a net driving electro‐osmotic force, favouring reabsorption, of 4 mmHg developed. The charges and the electro‐osmotic force was found to be essential for protein transport, since if the membrane was uncharged, the transport and interstitial concentration of e.g. albumin was twice as high. The glomerular capillaries seem to have a more homogeneous structure, that is in essence a one‐pore system; the pore radius was 44 Å, the total pore area over pore length 2.8 cm and the concentration of negative fixed ch

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1988.tb08429.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

The two major renal prostaglandins PGE2and PGI2are partly metabolized during a single passage of the kidney. To examine whether stopping glomerular filtration affected the renal degradation, PGE2and PGI2were infused into the suprarenal aorta of dogs during ureteral occlusion. Prostaglandin synthesis was blocked by indomethacin, 10 mg kg‐1b.w. i.v. About 20% of PGI2and 80–90% of PGE2were metabolized during one passage through the kidney. Prostaglandin degradation and arterial input were proportional (r>0.95). Compared to control conditions at free urine flow, PGI2degradation was not changed, whereas the degradation of PGE2was slightly increased by ureteral occlusion. Ethacrynic acid might reduce degradation of PGE2by inhibiting two degradation enzymes. To examine the influence of ethacrynic acid, PGE2was infused in different doses into the suprarenal aorta of dogs before and after administration of ethacrynic acid 3 mg kg‐1b.w. i.v. At all dose levels of PGE2, 75–80% was degraded by one passage through the kidney, whether ethacrynic acid was administered or not. However, although ethacrynic acid did not alter the total renal output, the urinary fraction was reduced from 20–30% to 10–15%. We conclude that degradation of both PGE2and PGI2is mainly confined to the blood vessels, and that ethacrynic acid in conventional doses does not prevent degradation of PGE2, but redistributes PGE2output from urine to renal v

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1988.tb08430.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Because chronic infusions of adrenalin (A) produce hypertension in rats, it has been suggested that A is a mediator of stress‐induced hypertension. In order to test the hypothesis that lowering A will attenuate stress‐induced hypertension, rats who had their adrenal medullae removed (ADM) and sham‐operated controls were subjected to chronic stress. All subjects were offspring of a cross between spontaneously hypertensive and Wistar‐Kyoto rats. Prior to chronic stress, systolic pressures were the same in the two groups. The stress consisted of 60 2‐h sessions of shock‐shock conflict during 18 weeks. After conflict stress, the rats were implanted with arterial catheters and allowed two days to recover. The resting mean arterial pressure (MAP) was 141.2 mmHg in the ADM group and 142.3 mmHg in the Sham group. Cardiovascular responses to acute stress were then examined. The rats were transferred to a test‐box and subjected to pulsed foot shocks (0.5‐s duration, 5‐s intervals) for 5 min. TheMAPincrease after transfer was 22.3% in the ADM and 4.2% in the Shams (P<0.001). After termination of the shocks, theMAPwas elevated 22.2% above baseline in the ADM and 8.1 % in the Shams (P<0.02). Five minutes after foot shocks theMAPincrease was 21.6% in the ADM and 7.2% in the Shams (P<0.02). Adrenal demedullation was effective in attenuating plasma A during stress and reduced the plasma noradrenaline response. Therefore, the larger pressor responses of the ADM group seem to result from attenuation of β‐adrenoreceptor‐mediated dilation of skeletal muscle vasculature. If lowering A has a beneficial effect, it may have been offset by attenuation of β

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1988.tb08431.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Spinal cord blood flow (SCBF) and its response to alterations in blood gases and to systemic hypotension, haemodilution and barbiturate anaesthesia were measured in 47 rats at the level of Th 7–8 by quantitative autoradiography with [14C]iodoantipyrine ([14C]IAP) as tracer. During normocapnia and normoxia the meanSCBFvalues in the grey and white matter were 94 ± 21 and 17 ± 3mlmin‐1100 g‐1, respectively.SCBFwas highly dependent onPaCO2. Thus in hypercapnic animals (PaCQ2>9 kPa) SCBF was increased in grey and white matter to 228 ± 22 and 54 ± 7mlmin‐1100 g‐1while during hypocapnia (PaCO2<3.9 kPa) it was decreased to 64 ± 14 and 11 ± 2 ml min‐1100 g‐1, respectively. Mean arterial blood pressure (MABP) was reduced by withdrawal of blood to 80 ± 8 mmHg in a light hypotension group and to 53 ± 11 mmHg in a severe hypotension group, compared with 126 ± 13 mmHg in a control group. There was no significant difference inSCBFbetween the control group and the hypotension groups, suggesting that autoregulation is maintained down to anMABPof at least 50 mmHg. Normovolemic haemodilution, with a reduction of the haematocrit from 50 ± 2 to 33 ± 3, increasedSCBFto 113 ± 9 ml min‐1100 g‐1in grey matter and to 21 ± 12 ml min‐1100 g‐1in white matter. Thirty minutes after an intraperitoneal injection of pentobarbital at 40 mg kg‐1body weight,SCBFwas not significa

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1988.tb08432.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

The influence of voluntary physical exercise in running wheels on myocardial function, cardiac oxygen utilization and cardiovascular response to emotional stress was analysed in the spontaneously hypertensive rat. After 6 weeks of exercise, a significant increase in resting cardiac output was found, which was due to an elevation of stroke volume. However, voluntary training for 12 weeks had no effect on resting blood pressure or on the blood‐pressure response to mental stress. Cardiac function was also examinedin vitro.At a low aortic diastolic pressure, it was markedly augmented in trained spontaneously hypertensive rats. At high aortic diastolic pressure, maximal cardiac function was similar in the two groups. Myocardial oxygen consumption (μmol min‐1g‐1) for a given level of external work was reduced in trained, compared with non‐exercised control spontaneously hypertensive rats. Chronic physical exercise thus greatly improved myocardial function at a subnormal perfusion pressure, suggesting better nutritional supply to the myocardium, probably created by an increased capillary surf

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1988.tb08433.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Under the assumption that a ventricle and its arterial load are normally matched according to work optimization, a relation between left ventricular (LV) mechanical performance as described by the slope (Emax) of the end systolic pressure‐volume relationship (ESPVR), mean systolic pressure during ejection (mSLVP), and stroke volume (SV), is proposed: optimum Emax=E=mSLVP/SV.Slope (Emax) was obtained, in 6 dogs and 9 rabbits, by establishing relations among ejected volume andLVdiameter squared (D2) in control beats, and among pressure and D2at end systole (ES) in series of beats of varying load, accomplished either by acute aortic constriction (AOC) or inferior caval occlusion (IVCO). Slope in dogs was also obtained by direct measurements of ventricular volume by a conductance catheter and the results were compared with the above method. A dimensionless index, α= Emsx/E', (optimal value = 1.0) was calculated to indicate how well the ventricle and arterial system were matched. In dogs,E= 10.9 ± 2.1 mmHg ml‐1, Emax= 8.1 ± 2.6 (AOC) and 7.1 ± 2.5 (IVCO), hence α= 0.79 ± 0.23 (AOC) and 0.68 ± 0.15 (IVCO). In rabbits,E= 54.1 ± 20.0 mmHg ml‐1,Emax= 64.8 ± 15.9 (mmHg ml‐1), hence a = 1.23 ± 0.33. α=1.0 fell outside the 95% confidence interval only in experiments of dogs

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1988.tb08434.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Atrial natriuretic peptide (ANP) was measured in plasma during acute volume load in conscious, spontaneously hypertensive rats (SHR) and normotensive Wistar‐Kyoto (WKY) rats. During basal conditions immunoreactive ANP were similar in the SHR (630 ± 56 pmoles 1‐1) and the WKY (657 ± 114 pmoles 1‐1) groups. An acute 10% and 20% whole blood volume expansion resulted in a linear increase in immunoreactive plasma ANP in the WKY. In the SHR the increase in plasma ANP was attenuated during the 20% volume load. During the 10% and 20% volume load central venous pressure (CVP), central blood volume (CBV) and cardiac output increased relatively more in the SHR compared with the WKY group. In contrast, the increase in peripheral blood volume (PBV) and decrease in heart rate (HR) was attenuated in the SH rats. In the SHR group there was a shift of the ANPvs. CVPand ANPvs. CBVcurves to the right compared with the WKY. We conclude that acute volume loading is a potent stimulus for ANP release in WKY as well as SHR. However, in the SHR, ANP release was blunted in spite of the increased centralization of the volume load in this rat strain. Thus, the decreased reponsiveness of the ANP hormonal system may contribute to the development and maintenance of hypertension in this genetic form of hyper

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1988.tb08435.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

The effects of the thromboxane‐receptor antagonist AH 23848 were investigated on isolated feline basilar arteries (BA). AH 23848 (10‐6mol l‐1) had no effect on contractions induced by 5‐hydroxytryptamine or potassium, whereas the drug (10‐8‐10‐6mol 1‐1) induced a parallel shift to the right in contractions induced by the thromboxane A2mimic U46619. There was no depression of the maximum contraction, indicating competitive antagonism. The Schild plot revealed a slope index of unity with a pA2value of 8.46. In contrast, 10‐6mol l‐1AH 23848 depressed the maximum PGF2α‐induced contraction significantly from 100% to 13%. U46619 was able to induce a contraction amounting to 98 % if the drug was added on top of the PGF2α‐induced contraction in the presence of 10‐6mol l‐1AH 23848. The results provide strong support for previous suggestions that prostanoid‐induced contractions in the feline BA are mediated by two receptor subtypes, one of which can be classified as a thro

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1988.tb08436.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY