Calcium transport in canine renal basolateral membrane vesicles. Effects of parathyroid hormone.

The effects of parathyroid hormone were studied on Ca2+ fluxes in canine renal proximal tubular basolateral membrane vesicles (BLMV). Efflux of Ca2+ from preloaded BLMV was found to be stimulated by an external Na+ gradient, and this was inhibited by the Na+ ionophore, monensin, and enhanced by intravesicular negative electrical potentials, which indicated electrogenic Na+/Ca2+ exchange activity. There was a Na+ gradient independent Ca2+ flux, but membrane binding of Ca2+ was excluded from contributing to the Na+ gradient-dependent efflux. The Na+ gradient-dependent flux of Ca2+ was very rapid, and even 2- and 5-s points may not fully represent absolute initial rates. It was saturable with respect to the interaction of Ca2+ and Na+ with an apparent (5 s) Km for Na+-dependent Ca2+ uptake of 10 microM, and an apparent (5 s) Vmax of 0.33 nmol/mg protein per 5 s. The Na+ concentration that yielded half maximal Ca2+ efflux (2 s) was 11 mM, and the Hill coefficient was two or greater. Both Na+ gradient dependent and independent Ca2+ efflux were decreased in BLMV prepared from kidneys of thyroparathyroidectomized (TPTX) dogs, and both were stimulated by parathyroid hormone (PTH) infusion to TPTX dogs. BLMV from TPTX dogs exhibited significantly reduced maximal stimulation of Na+ gradient-dependent Ca2+ uptake with an apparent (5 s) Vmax of 0.23 nmol/mg protein per 5 s, but the apparent Km was 8 microM, which was unchanged from normal. The Na+ gradient independent Ca2+ uptake was also reduced in BLMV from TPTX dogs compared with normal. Thus, PTH stimulated both Na+/Ca2+ exchange activity and Na+ independent Ca2+ flux. In vivo, the latter could result in an elevation of cytosolic Ca2+ by PTH, and this might contribute to the observed decrease in solute transport in the proximal tubule.

Na+-Ca2+ exchange and calcium permeability in canine basolateral membrane vesicles: the effects of dibutyryl cAMP and specific inhibitors.

The role of dibutyryl 3',5'-cyclic adenosine monophosphate (dibutyryl cAMP) as putative second messenger for parathyroid hormone (PTH) in regulating canine proximal tubular basolateral membrane Na+-Ca2+ exchange and passive calcium permeability was assessed, as was the nature of this passive calcium permeability. Dibutyryl cAMP (50 mg) infused in vivo over 30 min increased fractional phosphate excretion from 4.9 +/- 1.8% to 20.5 +/- 4.6%, P less than 0.05, n = 6, but had no effect on either passive Ca2+ efflux or sodium-stimulated Ca2+ efflux from Ca2+-preloaded basolateral membrane vesicles (BLMV). Both of these mechanisms have been previously shown to be stimulated by PTH. Further studies were performed to investigate the mechanism of the passive calcium flux. Calcium uptake by BLMV was blocked by lanthanum (La3+) but not by the calcium-channel blocker verapamil. La3+ blocked efflux of Ca2+ from preloaded vesicles when it was placed in the external solution. This La3+-blockable efflux was larger in potassium equivalent BLMV prepared from normal dogs than in BLMV prepared from thyroparathyroidectomized dogs. Benzamil produced 50% inhibition of sodium-stimulated Ca2+ uptake at 250 microM whereas neither amiloride nor diltiazem achieved 50% inhibition at the maximal doses studied. Benzamil, 1 mM, had no effect on passive calcium efflux and neither did the substitution of sucrose for potassium, which has been shown to affect Ca2+-Ca2+ exchange by the Na+-Ca2+ exchanger. This suggests that the calcium flux under potassium equivalent conditions was not mediated by Ca2+-Ca2+ exchange by the Na+-Ca2+ exchanger. These results demonstrate that the basolateral membrane of proximal tubular cells possesses both a Na+-Ca2+ exchanger inhibitable by benzamil and a passive calcium permeability not inhibited by benzamil nor by verapamil but by La3+. Neither of these two mechanisms of calcium flux was affected by dibutyryl cAMP whereas both have been shown to be stimulated by PTH.

In vitro cyclosporine toxicity. The effect of verapamil.

The epithelial cell line LLC-PK1, which expresses many proximal tubular characteristics, was used to investigate the relationship between calcium, the calcium channel blocker verapamil, and cyclosporine toxicity. The LLC-PK1 cells took up cyclosporine when this was added in a concentration of 2 micrograms/ml, and this uptake was maximal at 30 min (112 +/- 3 ng cyclosporine/mg cell protein). At 12 micrograms/ml it inhibited the sodium glucose cotransporter, as assessed by phlorizin-inhibitable 14C-alpha-methyl glucopyranoside (alpha-MG) uptake (control 37.2 +/- 6.3, 12 micrograms/ml 21.2 +/- 1.1 mumol/hr/mg protein). Cyclosporine at 2 micrograms/ml did not affect cell growth after 5 days (control 945 +/- 60 micrograms cell protein per 25 cm2 flask, 2 micrograms/ml cyclosporine/ml 1046 +/- 32 micrograms protein/flask), even in the presence of 7.6 mM ionized calcium (862 +/- 37 micrograms protein/flask). Cyclosporine at 12 micrograms/ml inhibited cell growth (286 +/- 27 micrograms protein/flask), and raising the ambient ionized calcium concentration to 7.6 mM reduced cell growth further (91 +/- 6 micrograms protein/flask). Cyclosporine at concentrations of 2 and 12 micrograms/ml produced increasing cell vacuolation, as seen in vivo. Short-term uptake of 2 micrograms/ml cyclosporine could be inhibited by 1.0 mM and 0.5 mM verapamil (49 +/- 9.5 and 71 +/- 6.4 ng cyclosporine/mg cell protein, respectively, at 30 min). However, in the presence of 2 micrograms/ml cyclosporine 0.1 mM verapamil was toxic to the cells grown over five days (44 +/- 5 micrograms protein/flask). At 0.01 mM verapamil was not toxic to cell growth (921 +/- 29 micrograms protein/flask), but raising the medium calcium to 7.6 mM reduced cell growth (652 +/- 96 micrograms/ml). Inhibition of cyclosporine uptake did not occur with 0.01 mm verapamil (control 145.6 +/- 12.3 vs. 0.01 mM verapamil 150.4 +/- 3.8 ng cyclosporine/mg cell protein). The LLC-PK1 cell line represents a good in vitro model for cyclosporine renal tubular toxicity, as the in vivo observation of glycosuria and proximal tubular cell vacuolation in cyclosporine nephrotoxicity can be reproduced. In vitro this is shown to be associated with inhibition of sodium-dependent glucose cotransport. Verapamil inhibited cyclosporine uptake, but only at concentrations that were toxic to the cells. Verapamil potentiated rather than reduced the increased cyclosporine toxicity produced by increasing the medium calcium concentration. The suggested protective effect of verapamil against cyclosporine nephrotoxicity is therefore unlikely to be due to inhibition of cyclosporine uptake or of calcium entry into proximal tubular cells.

Transplant renal artery stenosis in 77 patients--does it have an immunological cause?

Transplant renal artery stenosis (TRAS) is a common complication after transplantation and is an important cause of graft dysfunction. Damage from graft rejection, trauma, and atherosclerosis have been implicated as possible causes. We reviewed all 917 patients transplanted in our unit since 1978 to study the prevalence, clinical features, and possible causes of TRAS. Seventy-seven patients with TRAS were identified. The detected incidence was 2.4% before the introduction of color doppler ultrasonography (CDU) and rose to 12.4% after CDU was introduced in 1985, giving an overall incidence of 8.4% during a mean follow-up period of 6.9 years. The TRAS group was compared with a control group of 77 transplanted patients matched for age, year of transplant, sex, and number of previous grafts. Mean ages for the study and control groups were 43.6 +/- 15 and 44.8 +/- 13.7 yr. A total of 25% of cases of TRAS were diagnosed within the first 8 wk of transplantation and in 60% within the first 30 wk (median = 23 wk). All patients were treated with angioplasty, 28 patients had recurrence of TRAS requiring multiple angioplasties (maximum 5) and 1 went on to have surgery. Angioplasty resulted in a significant fall in plasma creatinine. Patient and graft survival were significantly worse in the TRAS group: 69% vs. 83% (P < 0.05) and 56% vs. 74% (P < 0.05) (TRAS vs. Control), respectively. There was a significantly higher incidence of rejection, especially cellular rejection in the TRAS group, 0.67 vs. 0.35 episodes per patient (P < 0.01) (TRAS vs. Control). Recurrence but not occurrence of TRAS was associated with the use of cyclosporine.

Lipiduria in renal disease.

This article reviews the published data on lipiduria in both health and disease. Small amounts of lipid appear in the urine under normal circumstances but, in the nephrotic syndrome in humans, there is also a considerable amount of high-density lipoprotein in the urine as well as smaller amounts of other lipoproteins. Potential tubular re-uptake mechanisms for lipoproteins have been demonstrated in both animal and cell-culture models. In humans, there is no direct evidence for these specific re-uptake mechanisms--it is only through specific staining of renal biopsies for apolipoproteins that the presence of such mechanisms in intracellular vesicular structures is suggested. It is possible that lipoprotein filtration and re-uptake by the tubule are important mechanisms in tubular injury.

The use of captopril-DTPA scanning in the diagnosis of atherosclerotic renal artery stenosis in patients with impaired renal function.

We have analyzed our use of captopril-diethylene-triaminepentaacetic acid (DTPA) scanning in patients presenting to the Royal Free Hospital predominantly with renal impairment. The sensitivity was found to be as good in patients with bilateral disease or disease of a single kidney as in patients with unilateral disease. On a number of occasions, though, the scan suggested unilateral disease when bilateral disease existed. There were, however, a large number of patients for whom captopril-DTPA scanning was not performed because of severe renal impairment or the possibility of renal artery stenosis in a single functioning kidney.

Atherosclerotic nephropathy.

BACKGROUND: Lipid moieties may have direct or indirect effects on the kidney. The association of aortic atherosclerosis and renal artery stenosis has focused interest on this as an important cause of end-stage renal failure. This article seeks to examine the evidence for the entity of atherosclerotic nephropathy. METHODS: Published data on the incidence of atherosclerotic renal artery stenosis as the cause of end-stage renal failure are presented, as well as the associated features of atherosclerotic renal stenosis. RESULTS: Atherosclerotic renal artery stenosis (ARAS) has been estimated to be the cause of between 14 and 25% of patients reaching end-stage renal failure in older age groups. There is considerable evidence of proteinuria in patients with ARAS. Recent data have shown that renal length may decrease by 1 cm or more in 35% of kidneys with > 60% stenosis. However, other data suggest that renal function in kidneys without renal artery stenosis but with contralateral renal artery stenosis may be similarly decreased. CONCLUSION: Many processes contribute to renal dysfunction in atherosclerotic aortic disease. Although ischemia may play a role, there is considerable evidence that processes such as atheroembolic disease may be important, and it would be better to use the term "atherosclerotic nephropathy" for this important disease entity.

Proteinuria in atherosclerotic renovascular disease.

Proteinuria is well described in atherosclerotic renovascular disease (ARVD), but the prevalence is unknown, and the pathogenesis may vary between patients. Substantial proteinuria (> 2 g/day) however, would be regarded by many as atypical of ARVD. We studied 94 patients (52 male) with ARVD, median age 67 years (range 49-87). Digital subtraction angiography was performed on all patients. Protein was assayed in 24-h urine samples and GFR derived using the Cockroft-Gault formula. Forty-nine patients (52%) had proteinuria < 0.5 g/24 h. Proteinuria increased with worsening renal function. Biopsies from seven non-diabetic patients with substantial proteinuria showed: minimal changes (1); glomerular sclerosis with marked ischaemic changes (3); focal glomerulosclerosis (2); and athero-emboli (1). Proteinuria, rather than being indicative of other pathology, is often a marker of severity of parenchymal disorder in atherosclerotic nephropathy, which itself is the major determinant of renal dysfunction in patients with ARVD.

Presentation, clinical features and outcome in different patterns of atherosclerotic renovascular disease.

Atherosclerotic renovascular disease (ARD) is an increasingly important cause of renal failure. However, important features of the clinical presentation are not fully described, and the outcome after intervention by angioplasty remains controversial. Ninety-four patients with ARD diagnosed at angiography were reviewed. Twenty-four patients were diabetic. Thirty-nine patients had unilateral renal artery stenosis or occlusion (group A), 28 had bilateral stenosis (group B), and 27 had unilateral occlusion plus contralateral occlusion or stenosis (group C). Two years after presentation, actuarial patient survival was 96%, 74.3% and 47.1% in groups A, B and C, respectively (p < 0.001 for all differences); actuarial renal survival in surviving patients was 97.3%, 82.4% and 44.7%, respectively (p < 0.001 for all differences). Percutaneous transluminal balloon angioplasty (PCTA) was performed in 74 patients. Renal function improved in only a minority of cases, but was stable in 73% of nondiabetic patients 12 months after PCTA. Angioplasty was less effective in diabetic subjects, with only 53.3% having stable renal function at 12 months follow-up. Renal and patient survival were strongly related to the initial angiographic findings. In non-diabetic subjects, PCTA resulted in stabilization of renal function for at least one year in nearly three-quarters of cases, which suggests a benefit from intervention in this disease whose natural history is otherwise of progression.

The diagnostic value of urinary enzyme measurements in hypertension.

N-Acetyl-beta-D-glucosaminidase (NAG), beta-D-galactosidase, alkaline phosphatase (ALP) and leucine aminopeptidase (LAP) were assayed in the urine of 100 normal and 112 hypertensive subjects. Age-related urinary activities for these enzymes in the normotensive control subjects are presented. A new procedure for the assay of urinary ALP using 2-methoxy-4-(2'-nitrovinyl)phenyl (MNP) phosphate is described. Thirty-five of the hypertensive patients were considered to have primary renal disease. The urinary activity of NAG was increased in 27 (77%) of these patients and the detection of primary renal disease was not enhanced by measurements of the other urinary enzymes. Testing the urine both for NAG activity and protein, led to the detection of 91% of these patients. The assay procedures described are simple to perform and can be carried out in outpatient clinics. The measurement of urinary NAG activity is a cheap and reliable method for detecting renal disease in hypertensive patients but maximum diagnostic yield is achieved when proteinuria is determined as well.

Anosmia and isolated ACTH deficiency following a road traffic accident. Case report.

A 42-year-old man suffered a head injury in a road traffic accident and subsequently developed anosmia and isolated adrenocorticotropic hormone (ACTH) deficiency. There was no other evidence of pituitary dysfunction. No previous case of isolated ACTH deficiency following head injury has been reported.

A late complication of spousal kidney donation.

An 83-year-old female who had previously (32 years ago) donated a kidney to her husband presented with loin pain, confusion and oliguria. Acute renal failure and pulmonary edema necessitated emergency hemodialysis. The history and findings were thought to be consistent with acute renal artery occlusion on a background of atherosclerosis and severe renal artery stenosis. We present this case, not to imply that renal donation is a hazardous procedure, but rather as an illustration of a complication of donor nephrectomy that in a very large series has proved to be extremely rare. This case illustrates the point that even very rare events become more likely as the period of follow-up increases.

Atherosclerotic renovascular disease causing renal impairment--a case for treatment.

Renovascular disease is a potentially curable cause of renal failure. In a prospective survey over an eighteen month period atherosclerotic renal artery disease was the cause of renal failure in 14% of patients over the age of fifty years accepted for renal replacement therapy at this hospital. Ten patients were found to be suffering from atherosclerotic renovascular disease causing renal failure but in only one was treatment able to reverse renal failure. The major problem with this group of patients is the widespread nature of their disease affecting many other organs. Significant morbidity is associated with their investigation. Although potentially curable, atherosclerotic renovascular disease is a frequent cause of renal failure in patients over the age of fifty years but is also difficult to treat.

Para-aortic nodal irradiation for early stage testicular seminoma.

Early stage seminoma of the testis has an excellent prognosis when post-orchidectomy para-aortic and ipsilateral pelvic radiotherapy is given. However, studies on testicular lymphangiograms and the rarity of isolated pelvic nodal disease suggest that pelvic radiotherapy is not necessary, except in cases where there is the possibility of altered lymphatic drainage. We report on 27 patients with stage I and IIA seminoma treated between 1983 and 1989. Seventeen patients received radiotherapy to the para-aortic region only. There have been no pelvic recurrences. No long term complications have been encountered. We discuss the reported data which suggest that a reduced complication rate should result from the proposed field reduction. We conclude that irradiating only the para-aortic region in early stage seminoma is logical, should not increase the relapse rate and should reduce the complication rate.

Hyperfractionated accelerated radiotherapy for carcinoma of the oesophagus.

We report on 48 patients with carcinoma of the oesophagus treated by hyperfractionated accelerated radiotherapy. The patients, aged 46 to 93 years, were considered suitable for radiotherapy on their performance status irrespective of the presence of metastases. The radiotherapy was given three times a day over 2 weeks with a minimum of 3 h between treatments. The treatment was well tolerated acutely and to date there have been no unacceptable long-term side-effects. Dysphagia was improved in 39 (81.2%) patients. Product-limit survival was 35.7%, 18.5% and 12.3% at 1, 2 and 3 years. We conclude that this regime is feasible within the normal working day, well tolerated, effective and the shorter overall treatment duration desirable.

Use of the hepatic arterial circulation for renal revascularisation.

Renal artery stenosis is increasingly being diagnosed as a cause of hypertension and renal impairment. Surgical intervention can restore function and improve hypertension in selected cases. Over a 42 month period, 12 patients with atherosclerotic renovascular disease underwent surgical revascularisation using the hepatic arterial circulation. All had disease of both renal arteries and 11 had some degree of renal impairment, with five requiring dialysis before operation. There were two deaths within 30 days of operation, eight patients had improved renal function after operation and three of the patients previously on dialysis became dialysis free. The hepatorenal method of renal revascularisation is described and its advantages discussed.