Diminished glomerular capillary hydraulic conductivity precedes morphologic changes in experimental diabetes mellitus in the rat.

Glomerular ultrafiltration coefficient, Kf, is diminished in established diabetic nephropathy. To determine whether Kf is decreased because of a decrease in capillary area, A, and or in hydraulic conductivity, Lp, glomerular Kf and morphometric parameters were measured, and Lp was calculated in glomeruli of young rats with STZ-induced DM and in control rats. STZ was administered to Fischer 344 rats that weighted 50-75 g; glomeruli were examined after 3 or 5 mo of DM, and their structure and function was compared with that of control rats. The effects of insulin or of an ACEI, enalapril, also were assessed after 3 or 5 mo. Growth of DM rats was markedly impaired, and their ratio of kidney weight to body weight was increased. Ccr was proportional to rat weight, and the ratio of Ccr to body weight was not different in DM and control rats. At 3 mo, average volume of glomeruli isolated from DM rats was less than that of glomeruli from control rats. In contrast, glomerular volume after 5 mo was equal in DM and control rats. No increase in GBM thickness or mesangial volume was observed, nor was any decrease seen in GBM area in DM rats at 5 mo. Kf was lower in DM rats than controls after 3 mo, but not after 5 mo. The Lp of DM and control glomeruli did not differ at 3 mo, but was lower in DM at 5 mo. Insulin therapy improved somatic growth and increased kidney and glomerular size in DM rats; the kidney weight/body weight ratio remained elevated.(ABSTRACT TRUNCATED AT 250 WORDS)

Ambulatory blood pressure in type I diabetes mellitus. Comparison to presence of incipient nephropathy in adolescents and young adults.

AMBP measurements were obtained at 20-min intervals during the day and at 60-min intervals during the night in 38 adolescents and young adults (12-25 yr old) with type I diabetes, and in 36 healthy, nondiabetic control subjects of comparable age. The group of patients with elevated AER (greater than 15 micrograms/min) had higher mean 24-h sBP, dBP, and BPB (defined as the prevalence of systolic readings greater than 130 mm Hg or diastolic readings greater than 85 mm Hg) compared with both the group of patients with type I diabetes and AER less than 15, and the control group. The normal diurnal variation in BP and BPB was observed in the control group and the group with type I diabetes and AER less than 15, whereas the nocturnal decrease observed in the group with type I diabetes and AER greater than 15 was not statistically significant. Elevations in AMBP of the patient group with AER greater than 15 were reflected in random BP measurements. Even though the mean random BP measurements of all groups were within the normal range for age, the mean random sBP and dBP of the type I diabetes patients with AER greater than 15 was higher than both the control group and the group with type I diabetes and AER less than 15. The GFR, determined by the clearance of 99Tc-DTPA, was associated negatively with measures of AMBP and AER in the group with AER greater than 15.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of angiotensin-converting enzyme inhibition on renal function and albuminuria in normotensive type I diabetic patients.

Normotensive patients with insulin-dependent (type I) diabetes mellitus (n = 18) were given 25 mg captopril (b.i.d.) and placebo for 3 mo in a randomized double-blind crossover study. Patients had normal renal function, and none had retinopathy. Albuminuria was less than 20 micrograms/min in 12 patients and between 20 and 200 micrograms/min in the other 6. Patients were examined at the end of the placebo and captopril phases. Captopril caused little reduction in blood pressure obtained by 24-h ambulatory monitoring (systolic 126.0 +/- 2.7 to 123.9 +/- 2.4 mmHg, P less than 0.08; diastolic 74.2 +/- 1.9 to 72.1 +/- 1.9 mmHg, P less than 0.09). Captopril lowered glomerular filtration rate from 99.5 +/- 7.7 to 71.0 +/- 5.5 ml.min-1. 1.73 m-2 (P less than 0.01), whereas renal plasma flow (443.9 +/- 15.2 ml.min-1. 1.73 m-2) remained unchanged. Filtration fraction was reduced from 22.4 +/- 1.4 to 17.4 +/- 1.4% (P less than 0.01). Urinary albumin excretion was reduced from 59.1 +/- 0.15 to 27.7 +/- 13.9 micrograms/min (P less than 0.1). Reduction was related to the extent of initial albuminuria (r = 0.997, P less than 0.001), a relationship that remained significant after logarithmic transformation (r = 0.540, P less than 0.02). Dextran clearance was used to determine glomerular capillary function. Angiotensin inhibition caused reduction in effective glomerular pore size and also reduced flow via the nondiscriminatory shunt. Angiotensin inhibition in normotensive patients with type I diabetes was well tolerated. Reduction in albuminuria is mediated by a combination of hemodynamic changes and alterations in glomerular capillary function.

Recognition of hypertension and abnormal blood pressure burden with ambulatory blood pressure recordings in type I diabetes mellitus.

Ambulatory blood pressure (AMBP) measurements were obtained at 20-min intervals for 24 h in 25 subjects with insulin-dependent (type I) diabetes mellitus and 21 control subjects. The diabetic patients had normal kidney function (glomerular filtration rate 112.1 +/- 7.2 ml.min-1.1.73 m-2, renal plasma flow 459.0 +/- 23.4 ml.min-1.1.73 m-2) and were normotensive according to standard sphygmomanometer examinations. Mean +/- SE AMBP (systolic/diastolic in mmHg) measurements in diabetic patients (24 h, 131.7/77.2 +/- 2.9/1.8; 0600-2200, 132.3/78.4 +/- 2.9/3.4; 2200-0600, 125.1/75.7 +/- 3.9/3.4) significantly exceeded control values during all times (24 h, 121.8/70.3 +/- 2.9/1.9; 0600-2200, 120.7/71.8 +/- 2.6/2.0; 2200-0600, 108.2/61.5 +/- 6.6/2.7). Mean 24-h AMBP exceeded 135/85 mmHg in 49% of diabetic patients. The same threshold of 135/85 mmHg was used to determine the prevalence of abnormal measurements per time period (pressure burden). Pressure burden was increased twofold in diabetic patients compared with control subjects. Mean AMBP was significantly reduced at night in control subjects but not in diabetic patients. Changes in blood pressure were not related to kidney function in diabetic patients. AMBP recordings uncovered an increased prevalence of abnormal mean blood pressure, increased pressure burden, and a lack of diurnal variation of blood pressure in subjects with type I diabetes mellitus. These findings have important implications for early intervention strategies in diabetes mellitus because AMBP recordings correlate well with end-organ damage.

Acute polyuric renal failure after aspirin intoxication.

Reversible acute polyuric renal failure was observed in a patient after the ingestion of an unusually large toxic (125 g) dose of aspirin. Renal dysfunction occurred in the absence of volume depletion or underlying renal impairment. These observations emphasize the need for careful monitoring of renal function in all patients with aspirin intoxication.

Legionnaires' disease associated with rash and renal failure.

Legionnaires' disease is recognized as a multisystemic illness. Afflicted patients may have pulmonary, gastrointestinal tract, and central nervous system complications. However, dermal involvement is not well documented and renal insufficiency is uncommon and usually of mild severity. We report two consecutive cases of proven Legionella infection that were unusual in that a macular rash and profound renal failure requiring hemodialysis were noted. Skin biopsy specimens of the rash and autopsy findings suggest that these atypical features may have been mediated by the Legionella infection. Although it is not entirely clear from these two cases, we suggest that the skin and renal involvement may have been mediated by either a "toxin" elaborated by the organism, an immunologic response of the host to the organism, or some other unidentified mechanism.

Comparison of albumin excretion rate obtained with different times of collection.

This study was undertaken to assess the usefulness of different techniques for determination of albumin excretion rate (AER). Ninety patients with type I (insulin-dependent) diabetes mellitus and 45 with type II (non-insulin-dependent) diabetes mellitus, with AER/24 h of less than 200 micrograms/min, were included. All patients were free of major systemic complications of diabetes and overt kidney disease (mean serum creatinine 1.1 +/- 0.1 mg/dl, range 0.4-1.2 mg/dl). We compared timed day, night, and 24-h specimens, as well as timed spot specimens during water-induced diuresis. Most patients with type I (75 of 90) and type II (30 of 45) diabetes had AER less than 20 micrograms/min and showed significant differences in AER that were dependent on the collection time. Differences were diminished or absent with AER less than 20 micrograms/min. Sensitivity, specificity, and prediction rates of AER in different specimens were evaluated against 24-h AER. Use of albumin concentrations and albumin-creatinine ratios did not improve test performance in comparison with AER. Sampling time and the overall rate of AER influenced measurement of urinary albumin excretion. Day or 24-h AER is most useful to determine the presence of abnormal AER. AER and albumin concentration in spot samples are of limited use for initial screening and frequently require day or 24-h specimens of AER for confirmation. Day or 24-h AER should be used for long-term follow-up of the diabetic patient.

Fluorescent analysis in polarized MDCK cell monolayers: intracellular pH and calcium interactions after apical and basolateral stimulation with arginine vasopressin.

Intracellular calcium ([Ca2+]i) and hydrogen ion concentrations (pHi) are important regulators of cell function. Those ions also may interact and it is important, therefore, to measure their concentrations simultaneously. In the present studies we used a system developed for that purpose, a fluorescent emission ratio technique for simultaneous analysis of calcium (Indo-1) and pH (SNARF-1) in single cells at video rates, and determined if arginine vasopressin (AVP, 12.5 mumol/l) evoked [Ca2+]i and pHi signals interact in MDCK cells. We also employed a simple system for analysing the side specific (basolateral or apical) application of agonist to polarized cell layers on permeable membranes. AVP is found to evoke simultaneous changes in both pHi and [Ca2+]i. Basolateral application induced transient acidification, followed by partial recovery, and a [Ca2+]i transient with kinetic pattern similar to that of the pHi. Apical application also caused a mirror image pHi and [Ca2+]i pattern but of smaller magnitude (no peak). Selective removal of extracellular calcium ([Ca2+]e) or sodium ([Na+]e) dissociated the pHi and [Ca2+]i responses in both cases. Na+e removal abolished the pHi changes, but not the [Ca2+]i transients. [Ca2+]e removal abolished the [Ca2+]i changes and reduced, but did not abolish, the pHi responses. Thus, AVP induces pHi changes which are modified by calcium while calcium signalling is not modified by changes in pHi.

Calcium regulation of intracellular pH in pituitary intermediate lobe melanotropes.

The regulatory activities of both intracellular calcium ([Ca2+]i) and intracellular pH (pHi) have greatly increased interest in the study of their interdependence. We have designed an epifluorescence video microscope that will image the fluorescence from two ratio dyes, indo-1 (for [Ca2+]i) and SNARF-1 (for pHi) at video rates. We examined primary cultures of pituitary intermediate lobe melanotropes loaded with both dyes. After experimentation, cells were positively identified by fluorescence immunohistochemistry. K(+)-induced depolarization of melanotropes produced increases in [Ca2+]i due to activation of L-type Ca channels. A secondary Ca2+ peak or oscillations were often seen. After treatment with carbonyl cyanide m-chlorophenylhydrozone, depolarization produced a rise in intracellular [Ca2+]i as well as oscillations. After thapsigargin or cyclopiazonic acid treatment, depolarization produced a primary Ca2+ elevation, but the secondary Ca2+ changes disappeared. This suggests that the oscillations were due to Ca2+ release from an endoplasmic reticulum type of intracellular store. All of these increases in [Ca2+]i were also directly coupled to a rise in intracellular H+. The close association between intracellular Ca2+ and H+ suggests that the observed pHi changes were due to the release of H+ upon binding of Ca2+ to intracellular buffers. This direct obligate coupling of intracellular Ca2+ and H+ suggests the possibility that pH-dependent cellular processes are directly activated by sudden increases in intracellular Ca2+ levels. This second messenger type of signaling system would be activated whether the Ca2+ was released from intracellular stores or entered the cell via plasma membrane Ca2+ channels.

Single-dose subcutaneous iodine-131-iodohippurate for determination of renal plasma flow.

Subcutaneous administration of a single dose of 131I-iodohippurate was used for determination of renal plasma flow (RPF) in 20 subjects during water diuresis. Slow release of tracer (200 microCi) permitted serial clearance measurements over 5 hr that were compared to standard, constant infusion, PAH clearance (mean 379.5 +/- 34.9 ml/min/1.73 m2, range 50.9 to 696.3 ml/min/1.73 m2). RPF(Isotope) was 424.9 +/- 30.3 ml/min/1.73 m2 (range 144.4 to 746.5 ml/min/1.73 m2) and highly correlated with RPFPAH (r = 0.883, p less than 0.0001). This technique permits prolonged studies of renal plasma flow under steady-state conditions without constant infusion.

Renal protective effects of enalapril in hypertensive NIDDM: role of baseline albuminuria.

The primary results of a three-year prospective, double-blind, placebo-controlled trial in non-insulin-dependent diabetic (NIDDM) patients show that an anti-hypertensive regimen, which includes the ACE inhibitor enalapril, preserves renal function to a greater extent than therapy with antihypertensive agents excluding ACE inhibitors (J Am Soc Nephrol 3:335, 1992). The influence of baseline urinary albumin excretion on the renal protective effects of enalapril treatment in these subjects was the objective of this further analysis. Adequate data were available in 121 patients of the 165 hypertensive NIDDM individuals studied [baseline glomerular filtration rate (GFR) 30 to 100 ml/min/1.73 m2]. Twenty-four hour urinary excretion of albumin (UAE), protein, urea nitrogen, creatinine and isotopically determined GFR were measured at baseline and six month intervals. Glycemic control and blood pressure regulation were assessed every three months. The rate of loss of GFR was significantly greater in patients with overt proteinuria at baseline (UAE > 300 mg/24 hr) as compared to patients with baseline sub-clinical proteinuria (UAE < or = 300 mg/24 hr). Antihypertensive treatment with enalapril preserved GFR significantly better (P < 0.01) in the patients with sub-clinical proteinuria at baseline (UAE < or = 300 mg/24 hr) than other antihypertensive treatments which excluded the ACE inhibitor. Furthermore, only 7% of the enalapril-treated group progressed to clinical albuminuria compared to 21% of control treated patients. Although the enalapril-treated group had a lower mean blood pressure during the maintenance period, no correlation between blood pressure (systolic, diastolic or mean arterial) and rate of change of GFR was observed.(ABSTRACT TRUNCATED AT 250 WORDS)

Principles, uses, and complications of hemodialysis.

Hemodialysis replaces missing renal function, and it does so incompletely. Current technology provides for reliable and flexible treatment strategies guided by patient's well-being and careful evaluation of plasma urea concentrations. Hemodialysis is indicated in many medical emergencies, notably fluid overload and hyperkalemia, and all types of renal failure. Hemodialysis requires a sizable effort and a significant commitment of time by both patients and professionals and is not suited for every patient with renal insufficiency. Notable treatment-related side effects include cramps, hypotension, problems with blood access, and reactions to dialyzer membrane materials. Far from treating underlying disease, hemodialysis extends life and permits the expression of much progressive multisystem disease. Cardiovascular disease is the most common comorbid condition and cause of early mortality.

Malabsorption of calcium and phosphate in chronic renal failure: 32P and 45Ca studies in dialysis patients.

A modified double-isotope method was used to determine the absorption of calcium and phosphate in patients with chronic renal failure. Eight hemodialysis patients and six healthy control subjects received an intravenous dose of 45calcium and 32phosphate and an oral tracer dose of 45Ca and 32P was administered two weeks later. Timed plasma samples were obtained on each occasion to determine fractional absorption rates and cumulative absorption of either tracer from both tracer sets with deconvolution analysis. Stool collections were analyzed. Calcium absorption in normal subjects peaked at 12% over fifteen minutes at one hour and declined rapidly thereafter. Absorption was essentially complete at four hours and cumulative absorption at this time was 72 +/- 6%. The pattern of phosphate absorption was similar and cumulative absorption at 4 hours was 80 +/- 3%. Calcium absorption in dialysis patients was significantly impaired with a flattened profile, a maximal 15-min absorption rate of 2% and cumulative 4-h absorption of 20 +/- 2%. Phosphate absorption in dialysis patients was also impaired to a comparable degree with a maximal rate of 3.6% and a more delayed cumulative total of 35 +/- 5%. Stool data showed good agreement with deconvolution analysis in volunteers but always overestimated absorption in patients. Sequential double isotope analysis provided a simple and convenient method for the concurrent estimation of calcium and phosphate absorption in humans.

Cerebral, myocardial and cutaneous ischemic necrosis associated with calcific emboli from aortic and mitral valve calcification in a patient with end-stage renal disease.

We report the case of a 57-year-old diabetic male with chronic renal failure who developed secondary hyperparathyroidism and calcification of mitral and aortic valves and interatrial septum. Multiple ischemic lesions developed in the skin of hands, feet and penis, and in the brain, and these were presumed to be due to septic emboli from cardiac valvular infective endocarditis. Multiple blood cultures were negative, however, and despite antibiotic therapy the patient expired. Autopsy (limited to trunk) demonstrated multiple calcific emboli in the heart and spleen, apparently derived from the prominent calcific deformities in the aortic and mitral valves. These were associated with acute and organizing myocardial infarcts and acute splenic infarcts, suggesting that the multiple ischemic lesions in the brain were also due to calcific emboli. A possible contributory component of infective endocarditis, however, was indicated by postmortem cultures of aortic and mitral valves positive for Enterococcus faecium. Calcific embolism is a rarely recognized but potentially lethal complication of end-stage renal disease, and the clinical diagnosis and the preventive therapeutic options for the control of the product of calcium and phosphate and/or parathyroidectomy should be considered.

In vitro effects of cyclosporine on glomerular function.

Cyclosporine A (CsA) causes vasoconstriction and decrease in glomerular filtration rate. Experiments were conducted in isolated glomeruli to study effects of CsA of glomerular perfusion and independent of systemic or renal factors. CsA caused a dose dependent decrease in glomerular volume consistent with mesangial contraction. The ultrafiltration coefficient Kf was significantly lower after incubation in 4 X 10(-4) M CsA when compared to control (2.81 +/- 0.2 vs 5.19 +/- 0.5 nl/min X mm Hg; p less than 0.001). Hydraulic conductivity Lp was diminished by CsA from 2.69 +/- 0.11 to 1.41 +/- 0.05 microliter/min X mm Hg X cm2 (p less than 0.001). These findings demonstrate a direct effect of CsA on the glomerulus which must be considered in addition to drug-induced changes in perfusion and tubular function.

Urate excretion by the isolated perfused rat kidney and modification by drugs.

Urate excretion in the isolated perfused rat kidney was studied over a wide range of perfusate urate concentrations (13.9-376.8 microM). Fractional excretion of urate (FEurate) averaged 57.9 +/- 2.0% (range, 58.5-59.6%), showed marked interanimal variability, but was not dependent on the perfusate-free urate concentration. In paired experiments, the effects of five drugs (probenecid, pyrazinoate, furosemide, salicylate, and oxonate) on FEurate were evaluated. A low concentration of pyrazinoate (0.2 mM) decreased FEurate (62.0 +/- 1.9 vs 53.8 +/- 2.4%, P less than 0.05), as did 0.8 mM pyrazinoate (59.5 +/- 2.4 vs 48.4 +/- 2.7%, P less than 0.05). Probenecid (1 mM) decreased FEurate (59.3 +/- 3.1 vs 52.0 +/- 2.5%, P less than 0.05) but 2.5 mM probenecid did not alter FEurate (48.0 +/- 6.3 vs 47.8 +/- 6.9%). Oxonate (0.1 mM) also decreased FEurate (75.8 +/- 4.2 vs 67.1 +/- 2.1%, P less than 0.05) while 0.2 mM oxonate had no effect (66.4 +/- 3.5 vs 61.5 +/- 4.6%). Neither salicylate nor furosemide affected FEurate, although both drugs caused a saliuresis and diuresis. Thus, urate transport in rat kidneys in vitro is not dependent on urate concentration, unlike man. Some drugs known to affect urate excretion in humans and rats did not have similar effects in isolated kidneys. Isolated organ studies provide additional information is understanding renal urate handling.

Excretion of para-aminohippurate in the isolated perfused rat kidney: net secretion and net reabsorption.

1. The excretion of para-aminohippurate (PAH) in the isolated perfused rat kidney was examined over a wide range of perfusate PAH concentrations (15 microM to 6 mM). PAH excretion increased steadily over the range of perfusate concentrations, reaching a maximal excretion rate of 3.28 mumol/min at a free-PAH concentration of 6 mM. 2. Tubular transport of PAH was evaluated from the difference between ultrafiltered PAH and excreted PAH. Net PAH secretion was observed at low perfusate free PAH concentrations. Net PAH transport was zero at a perfusate free PAH concentration of 2.1 mM. Above this level there was progressive net reabsorption. 3. Probenecid (2.5 mM) decreased PAH secretion to 18% of the initial value at 129 microM-free PAH (P less than 0.05). Probenecid had no effect on net reabsorption of PAH at high perfusate levels of the anion. 4. Alanine (5 mM) decreased net PAH secretion by 50% at low free PAH concentrations (P less than 0.05) and decreased net PAH reabsorption by 50% at at a free PAH concentration of 6 mM (P less than 0.05). These effects could not be related to effects of PAH, probenecid or alanine on glomerular filtration rate (GFR), vascular resistance or electrolyte excretion. 5. The results confirm the existence and integrity of the proximal tubular organic anion secretory system in the isolated kidney. In addition, net PAH reabsorption occurs at high perfusate levels.

Use of an extracorporeal arterio-venous shunt and capillary tubes for frequent micro-blood sampling in rats.

Because of the importance of frequent sampling during kinetic analysis, we have developed a method that permits frequent, reliable, and rapid access to the blood stream in rats. The method comprises the establishment of an extracorporeal arterio-venous shunt between femoral blood vessels. Quantitative samples of whole blood and plasma are obtained with capillary micro hematocrit tubes. The small sample volume permits repetitive analysis without major changes in hematocrit. There is good agreement between these measures and ordinary pipetting techniques. Kinetic analysis showed good resolution with close correspondence between actual measurements and the final curve of best fit. This method could be employed advantageously in small conscious animals, when frequent small samples are required by experimental design.

Renal adenocarcinoma and acquired cystic disease in chronic hemodialysis patients.

Three chronic hemodialysis patients developed renal cell adenocarcinoma with evidence of acquired cystic disease in two. The incidence of renal cancer in this study population of 0.27% per year is 50 times greater than that expected in general. The cancers appeared to develop at different rates. In one patient examined by serial computed tomography (CT) over 2.5 years, the tumor progressed rapidly. In the other two patients, the process was more idolent. On the basis of our experience, we recommend that dialysis patients be screened for acquired cystic kidney disease (ACKD) and renal tumors by sonography or CT. Patients with ACKD should be observed at regular intervals by CT for the development of possible tumor.

Dialysis leukopenia, hypoxemia, and anaphylatoxin formation: effect of membrane, bath, and citrate anticoagulation.

The goal of these prospective studies was to determine the effect of different dialyzer membranes and dialysate composition on leukopenia and hypoxemia during hemodialysis with citrate anticoagulation. Significant early leukopenia was found with a cuprophane membrane, while a cellulose acetate membrane was associated with mild early leukopenia. Bath composition had no effect. Bicarbonate dialysate, compared with acetate, eliminated hypoxemia in cellulose acetate membranes and reduced its degree and duration with cuprophane. Membrane composition had no effect on hypoxemia during acetate dialysis. The findings indicate that leukopenia is directly and exclusively related to membrane composition while hypoxemia only relates in part to membrane effects. Serial determinations of complement components C3a and C5a showed significant increases in parallel with leukopenia during heparin anticoagulation, but the anaphylatoxin concentration changes were dissociated during dialysis with citrate anticoagulation. The concentrations of anaphylatoxins C3a and C5a appear not to be directly related to dialysis-induced leukopenia. The dissociation between anaphylatoxin concentrations and leukopenia may be related to changes in generation or unmasked changes in leukocyte response. Citrate anticoagulation may provide a useful probe for further studies on membrane-leukocyte interactions in vivo.