摘要:

Renal autoregulation of blood flow (RBF) and glomerular filtration rate (GFR) were examined in 10 conscious foxhounds under a normal sodium diet before and after a continuous intrarenal converting—enzyme inhibition (CEI) or during the application of the angiotensin II antagonist saralasinm®. In order to prevent α‐adrenergic interference, phenoxybenzamine was infused into the renal artery. In contrast to studies performed in salt depleted dogs there was no impairmentof RBPorGFRautoregulation after CEI or saralasin®. Renal blood flow was autoregulated at a level of 3.81 ± 0.18 ml min‐1g‐1in the control group, 3.98 ± 0.16 ml min‐1g‐1after CEI and 3.97 ± 0.41 ml min‐1g‐1after saralasin®. The lowest point of autoregulation was very much the same between the individual groups (control: 65.0 ± 1.4 mmHg; CEI: 66.5 ± 4.6 mmHg; saralasin®: 67.4 ± 3.2 mm Hg).GFRacted in a similar manner (autoregulation level control: 0.50 ± 0.03 ml min‐1g‐l; CEI: 0.52 ± 0.05 ml min‐1g‐1; saralasin®. 0.50 ± 0.04 ml min‐1g‐1). The lowest pressure ofGFRautoregulation differed slightly more (control: 81.5 ± z. z mmHg; CEI: 93.2 ± 4.2 mmHg; saralasin®: 85.9 ® 2.1 mmHg). The results suggest that the renal autoregulationof GFRandRBFis independent of the renin‐angiotensin syst

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1988.tb08452.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

To investigate the vasoreactivity of the vessels of the juxtamedullary vasculature, measurements were made of the red blood cell flux (Qrbe) in the vasa recta of the exposed renal papilla of anaesthetized rats by means of fluorescently labelled erythrocytes. The flux was measured before and after intravenous administration of the calcium entry blocker verapamil, which was infused in two different doses. A control group receiving vehicle was studied in parallel. The lower dose of verapamil (0.6 mg h‐lkg‐1body wt) increasedQrbeby 30 ± 6% (n =9,P<0.05, mean ± I SEM) and reduced the systemic blood pressure by 6% (P<0.05). The osmolality of urine samples from the papillary tip remained statistically unchanged (1199 ± 60vs. 1186 ± 102 mosm kg‐1H2O). In the animals receiving the higher dose of verapamil (2.4 mg h‐1kg‐1body wt), Qrbcincreased by 39 ± 7% (n =10,P0.05) and the blood pressure was reduced by 9% (P<0.05), while urine osmolality was unchanged (1104 ± 110vs. 1264 ± 123 mosm kg‐1H2O). In the time control group there was no statistically significant change in Qrbe(+ 6 ± 8%,n= 10), blood pressure or urine osmolality (1006 ± 61vs. 1091 ± 70 mosm kg‐1H2O).The verapamil‐induced increase inQrbcis probably mainly mediated by a relaxation of the afferent arteriole of the juxtamedullary nephrons. The results confirm our previous indication of a high vasoreactivity in the vessels of the juxtamedullary vasculature. This vasoreactivity is a prerequisite for the large regulatory span of the renal medullary blood flow and consequently f

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1988.tb08453.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

The renal response to parathyroid hormone and the activity of alkaline phosphatase in kidney cortex were studied in weanling and adult rats. Clearance studies for the determination of glomerular filtration rate and phosphate excretion were started z h after sham operation or thyroparathyroidectomy in 24– or 40‐day‐old rats. Urine was collected under basal conditions and following infusions with 0.5 and 1.0μmol phosphate per 100 g body wt min‐l. For enzyme studies, rats aged 14–40 days were used, and the activity of alkaline phosphatase in renal cortical slices was determined. Glomerular filtration rate was not influenced by thyroparathyroidectomy or phosphate infusions. Plasma phosphate increased during phosphate infusions and was significantly higher in thyroparathyroidectomized rats in all clearance periods. Both the net and the fractional excretions of phosphate were higher in intact than in thyroparathyroidectomized rats and the phosphate‐retaining effect of thyroparathyroidectomy was similar in weanling and adult rats. Alkaline phosphatase activity in renal cortical slices increased between days 14 and 24 (1400–3190 IU mg‐1protein,P<0.01). During later development, no significant change was seen. It is concluded that the immature kidney of the weanling rats shows a parathyroid hormone‐dependent adaptation to acute phosphate loading, and that changes in alkaline phosphatase activity are consistent with a maturation of this system only during

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1988.tb08454.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Using a thermodilution technique for renal venous blood flow measurements, renal sympathetic nerve activity was evaluated in 10 healthy volunteers by measurements of noradrenaline (NA) and dopamine (DA) overflow to renal venous plasma. Renin release was measured simultaneously. At rest, arterial adrenaline (ADR) levels were 0.24 ± 0.03 nmol l‐1and NA and DA levels were higher in renal venous than in arterial plasma (12.4vs. 0.98 and 0.14vs. 0.09 nmol l‐1, respectively,P<0.01 for both). The renal extraction of ADR from arterial plasma was 40 ± 4%. ADR extractions were used to correct for the renal removal of NA or DA from arterial plasma when calculating the renal overflow of NA or DA to renal venous plasma. At rest, the thus corrected renal venous overflows of NA and DA were 228 ± 34 and 29 ± 3 pmol min‐1, respectively. Isometric handgrip exercise (IHG) increased renal vascular resistance (RVR) by 20% and NA overflow by 123 %, without altering renin release or DA overflow. Vasodilatation induced by dihydralazine (HYDR) increased NA overflow by 63% (P<0.05) and elevated DA overflow by 107 ± 59%. The renal DA/NA overflow ratio was reduced from 0.15 to 0.06 (P<0.01) during IHG, but was not altered by HYDR. Renin release increased by 377% after HYDR (P<0.001) and was correlated to the reduction of mean arterial pressure but not to changes in NA overflow. Thus, both IHG and HYDR increased renal sympathetic nerve activity, although differential effects on renin release and DA overflow were observed. The dissociation of renal NA and DA responses suggests that the human kidney may have a subset of dopaminer

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1988.tb08455.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

The effect of pretreatment with various substances protecting against oxygen free radicals on the leakage of proteins across the vessel walls of rabbit kidneys induced by ischaemia has been studied. The leakage of proteins was estimated from the difference between the 120‐min distribution space of [131I]albumin and the 5‐min distribution space of [125I]albumin, the latter mainly measuring the intravascular volume. Neither SOD (superoxide dismutase), catalase, allopurinol or two different Ca2+channel blockers (nifedipine, felodipine) could alone reduce the leakage induced by ischaemia. A combined pretreatment with SOD, catalase and nifedipine reduced the leakage in the cortex, and pretreatment with mannitol alone reduced the leakage in the cortex and outer stripe of the medulla. The results indicate that oxygen free radicals are involved in the leakage of proteins across the vessel walls induced by ischaemia, but that other mechanisms are involved as w

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1988.tb08456.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

When added to the apical solution of isolated frog skin, the calmodulin antagonist trifluoperazine (TFP)* stimulated the short‐circuit current (SCC) in a dose‐dependent manner. The increase inSCCwas due to an enhanced active transepithelial Na transport. After addition of TFP (15,μm) the intracellular voltage depolarized, showing that TFP acts by increasing the sodium (Na) permeability of the apical membrane. The TFP‐induced increase inSCCwas not accompanied by an increase in prostaglandin E2, release from the skins as observed by basolateral addition of TFP. When the apical Na concentration in fast‐flow experiments was changed from o to 50 mM, theSCCincreased promptly and then reclined. The presence of TFP in the apical solution abolished this recline. The apparent inhibition constant for amiloride changed in the presence of TFP from 1.42 ± 0.12 μM to 0.38 ± 0.05μM (n =11) and TFP abolished the inhibition ofSCCcaused by high apical Na concentrations. These observations indicate that TFP acts by abolishing the Na self‐inhibition of the Na channels. Calmidazolium and chlorpromazine stimulated theSCCto the same degree and in the same concentration range as TFP, suggesting that the effect of TFP was not mediated by the Ca2+calm

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1988.tb08457.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

The effect of reserpine treatment on renal sympathetic nerve activity and tissue levels of neuropeptide Y (NPY)‐like immunoreactivity (LI) and noradrenaline (NA) were studied in rats. Injection of reserpine (I mg kg‐1i. v.) caused a clear‐cut (about 50%) increase in rectified activity of the post‐ganglionic sympathetic nerves to the kidney within 15 min in chloralose‐anaesthetized rats compared to a saline‐treated control group. This increase in nerve activity was still maintained 120 min after the reserpine injection. The renal nerve activation was accompanied by a progressive fall in mean arterial blood pressure and an initial tachycardia. In a separate group of conscious rats, the levels of NPY‐LI (1.3 ± 0.06 pmol g‐1) and NA (1.6 ± 0.07 nmol g‐1) in the kidney were significantly reduced (by 74 and 83 %, respectively) 24 h after reserpine treatment (I mg kg‐1i. v.). The reserpine‐induced depletion of NPY‐LI, but not that of NA, was inhibited by pretreatment with the ganglionic blocking agent chlorisondamine or the alpha2‐adrenoceptor agonist clonidine, both of which are known to decrease renal sympathetic nerve activity. The tissue content of NPY‐LI in the right atrium (16.3 ± 0.7 pmol g‐1) was not reduced by reserpine. Arterial plasma NPY‐LI in the rat was high (222 ± 5 pmol l‐1), and this value did not change after pretreatment with reserpine, chlorisondamine or clonidine, indicating that, in the rat, circulating NPY‐LI is not a good indicator of sympatho‐adrenal activity. In conclusion, reserpine treatment is associated with an increase in the renal sympathetic nerve activity, which might be a factor contributing to a depletion of NPY‐LI from sympathetic nerve endings, while the depletion of NA seems to be less dependent on the nerve activity. It is also likely that increased release of NPY‐LI per nerve impulse, due to lack of alpha‐adrenergic auto‐inhibition of release after depletion of

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1988.tb08458.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

In the spontaneously hypertensive rat (SHR) as well as in the pathophysiological states with volume retention, high levels of atrial natriuretic factor (ANF) do not produce adequate diuresis and natriuresis. We have investigated the question whether the reduced effectiveness of ANF could be due to a reduction of the ANF binding. Evidence is provided by quantitative autoradiography with [125I]ANF than higher ANF plasma levels in SHRSP compared to normotensive WKY rats are associated with a reduced number of binding sites (25%) in the renal papilla as well as in the subfornical organ (69%). This could contribute to the reduced response of ANF in SHRSP.

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1988.tb08459.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

The renal handling of bovine and human superoxide dismutase (SOD) was investigated in Sprague—Dawley and Munich—Wistar rats. Under normal physiological conditions the half‐time of the major rapid component of the plasma elimination curve was estimated at 6.0 ± 0.5 min, the volume of distribution at 35.7 ± 3.3 ml kg‐1, i. e. the plasma volume and the corresponding plasma clearance at 4 ml min‐1kg‐1. After a single intravenous dose, most of the enzyme was distributed to and eliminated by the two kidneys, whereas the non‐renal clearance was low, 0.5 ml min‐1kg‐1. The single nephron filtration of SOD, as assessed from micropuncture of Bowman's space, was 10.4 ± 1.0 nl min‐1, which was 26 ± 2% of that for inulin. The total elimination of SOD by glomerular filtration would thereby be 2.5 ml min‐1kg‐1, i. e. the glomerular ultrafiltration process would account for the largest part of the elimination of SOD from circulating plasma. After the dosage of 20 mg kg‐1, about two‐thirds of the injected SOD was excreted as the intact molecule into the urine, whereas one‐third was found to be reabsorbed and metabolized by the proximal tubular epithelial cells. In animals suffering from unilateral post‐ischaemic acute renal failure, the elimination half‐time was 13 ± 1.9 min, a value which increased by 55 ± 5 min after bilateral functional nephrectomy. By contrast, the distributio

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1988.tb08460.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Six healthy subjects in random order underwent gastric bicarbonate secretion investigations, including stimulation with increasing doses of the cholinergic agonist carbachol, sham feeding, fundic distension and gastric instillation of 16, 16‐dimethyl prostaglandin E2. Bicarbonate secretion was measured by a computer‐based system which continuously recorded pH and PCO2of the effluent in a high‐volume gastric perfusion system. The peak 30 min gastric bicarbonate output in response to carbachol, 150 mg subcutaneously, was 114% (P<0.05). Vagal stimulation by sham feeding resulted in a corresponding increase of 112% (P<0.05), while fundic distension to a volume of 600 ml gave an increase of 114% (P<0.05). In comparison, the response to 80 μg 16, 16‐dimethyl prostaglandin E, was much greater, the peak bicarbonate output being increased by 245 % (P<0.05). Both sham feeding and fundic distension appear to be either submaximal stimuli of gastric bicarbonate secretion in man or may possess both stimulatory and inhibitory

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1988.tb08461.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY