The fanconi syndrome in Basenji dogs: a new model for renal transport defects.

The renal defects resulting in a Fanconi syndrome were seen in eight Basenji dogs by measuring renal clearance and in vitro amino acid and sugar uptake and performing histopathologic evaluations. Renal tubular handling of glucose, phosphate, sodium, potassium, uric acid, and amino acids was abnormal, and in vitro uptake of labeled lysine, glycine, and alpha-methyl-D-glucoside by renal cortical slices was impaired. Histopathology was normal except for enlarged nuclei in some renal tubule cells. These Basenji dogs, which may be genetically affected, represent a likely model for idiopathic Fanconi syndrome in humans.

Cystinuria in the maned wolf of South America.

Of 42 maned wolves in zoos or live-trapped in Brazil, 34 had excessive cystine in their urine. Renal clearance studies of five of the affected wolves revealed a variable defect for the reabsorption of cystine and dibasic amino acids. The renal tubular handling of other solutes including glucose, phosphate, sodium, potassium, and uric acid was considered normal. Urinary calculi composed of cystine were found in four wolves and proved fatal in three of them. With the exception of the high incidence in this species, this hereditary disease resembles the disorder described in dogs and humans.

Developmental changes of glycine transport in the dog.

The renal clearance of amino acids was measured in canine pups between 5 days and 12 weeks of age. The reabsorption of glycine was incomplete at 5 and 21 days, indicating a physiologic aminoaciduria of immaturity. An adult pattern of 97-100% reabsorption appeared by 8 weeks of age. The uptake of glycine by isolated renal tubules from 5-day-old, 3-month-old and adult dogs was examined towards an understanding of the events underlying this aminoaciduria. The initial uptake of 0.042 mM glycine by isolated tubules from the newborn was lower than that of the adult, but after 30 min of incubation the newborn surpassed the adult. A steady state of uptake was not achieved by the newborn even after 90 min of incubation, while it was achieved in the adult after 30 min. The uptake by the 3-month-old tubules resembled the adult at the early time points and the newborn at later points. With 1.032 mM glycine, a similar relationship of uptake between adult and newborn tubules was found, except with this concentration, the uptake by both the newborn and adult tubules reached a steady state. The concentration dependence of glycine uptake showed two saturable transport systems with similar apparent Km and Vmax values after 30 min of incubation for all three age groups. Determination of glycine flux by compartmental analysis revealed decreased influx and efflux in the newborn, but with a greater decrease in efflux, compared to adult. These changes of influx and efflux which accompany renal tubule maturation could contribute to the increased intracellular amino acid levels and decreased reabsorption of amino acids seen in the immature dog.

Chronic pressure-natriuresis relationship in dogs with inherited essential hypertension.

A genetic model of essential hypertension in the dog was studied to describe the phenotypic expression of the arterial pressure, as well as to determine the relationship between mean arterial blood pressure (MAP), hormone, and renal excretory responses to four different levels of sodium intake (5, 40, 120, 240 mEq/day) delivered intravenously and isotonically. This model was developed at the University of Pennsylvania (U/Penn) and termed Pennsylvania hypertensive dogs (PHD). The MAP was recorded beat-by-beat, 24 h/day, in 16 dogs. Water and sodium balances were determined daily for 4 days at each level of intake and blood samples were collected on the last day of each salt step for analysis of plasma renin activity (PRA), atrial natriuretic peptide (ANP), aldosterone (ALDO), and vasopressin (AVP). After the study, the dogs were designated as hypertensive (PHD-HT) when the 24-h average MAP was greater than 110 mm Hg and systolic pressure was greater than 160 mm Hg. Dogs that failed to meet both criteria were designated as normotensive genetic controls (PHD-NT). Although sodium was retained during the first day of each increase of salt intake in both groups, a return to balance was observed within the 4 days. There was no apparent change in the slope of the chronic renal function curve in either group of PHD studied, although the PHD-HT exhibit a curve shifted to a higher level of MAP. Plasma hormone levels in both groups of PHD studied responded in a manner similar to normal mongrel dogs with reductions of PRA, ALDO, elevations of ANP, and no change in AVP.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of the nonpeptide angiotensin II receptor antagonist DuP 753 on blood pressure and renal functions in spontaneously hypertensive PH dogs.

A colony of genetic hypertensive dogs with systolic blood pressure of 140 to 220 mm Hg and diastolic blood pressure greater than 100 mm Hg in the trained state was used. The objective of this study was to investigate the hemodynamic and renal effects of the novel angiotensin II receptor antagonist DuP 753 given intravenously to these dogs. Renal functions and blood pressure were measured 45 to 75 min after the intravenous administration of DuP 753 at 1, 3, 10, and 30 mg/kg and were compared to control (placebo) treatment. Arterial pressure was slightly but significantly and dose-dependently reduced by DuP 753. Glomerular filtration rate increased significantly in a dose-dependent manner. Similarly, effective renal plasma flow was dose-dependently increased. Filtration fraction was unchanged. Renal vascular resistance was significantly reduced in a dose-dependent manner at 3, 10, and 30 mg/kg of DuP 753. DuP 753 increased fractional sodium excretion at all doses and increased fractional potassium excretion only at the highest doses. The vasopressor effects of angiotensin I and II were dose-dependently inhibited by DuP 753. These data show that DuP 753 has beneficial renal hemodynamic effects and lowers arterial pressure in this canine model of essential hypertension.

Renal tubule reabsorption of amino acids after lysine loading of cystinuric dogs.

The renal reabsorption of cystine, lysine, arginine, and ornithine as well as other amino acids has been determined before and after lysine infusion in four normal and five cystinuric dogs. The large filtered load of lysine caused defective reabsorption of cystine in three of four normals and augmented the basal defect in all of the cystinuric dogs. Two of the cystinuric dogs responded with cystine clearances in excess of the glomerular filtration rate. The magnitude of increase of the reabsorptive defect for cystine observed after lysine infusion into the cystinuric dogs was unrelated to the extent of the basal defect. Two of the normal dogs and four of the five cystinuric dogs demonstrated defective arginine reabsorption after lysine loading, one of the cystinuric dogs having greater arginine excretion than the filtered load. Although normal dogs showed a moderate inability to reabsorb the large filtered load of lysine, three of the cystinuric dogs exhibited a -60 to -70% reabsorption, consistent with lysine secretion. Both normal and cystinuric dogs showed defective glycine absorption after lysine loading, but only cystinuric dogs showed variable defects in threonine, serine, histidine, methionine, and tyrosine when the basic amino acid was infused. Each cystinuric dog responded to lysine infusion in a different way, and the overall pattern of response differed from the normal, with evidence of induced secretion of cystine, lysine, and arginine in the affected dogs.

Spontaneous Fanconi syndrome in the dog.

Three dogs with spontaneous renal tubular defects similar to idiopathic Fanconi syndrome are characterized. Renal clearance studies revealed a fractional reabsorption of glucose ranging from 31% to 82%. Abnormal glucose thulium values were present in all dogs. A generalized aminoaciduria occurred in two dogs while one had aminoaciduria characteristic of canine cystinuria. Fractional reabsorption of phosphate ranged from 47% to 79%. In vitro uptake of alpha-methyl-D-glucoside was significantly depressed (p less than 0.001). In vitro uptake of amino isobutyric acid was similar to controls. Renal biopsy revealed nonspecific interstitial change in two dogs and normal histology in the other. These animals represent a useful new model for the study of renal tubular transport defects.

Cystinuria in dogs: comparison of the cystinuric component of the Fanconi syndrome in basenji dogs to isolated cystinuria.

Two animal models for cystinuria have been examined: the Basenji dog with Fanconi syndrome and cystine stone-forming dogs of various breeds. Brush-border membranes were isolated from these animals and uptake of D-glucose and L-cystine was characterized. Experiments with isolated brush-border vesicles from Basenji dogs with cystinuria as a component of the Fanconi syndrome showed diminished sodium-dependent D-glucose uptake but no decrease in L-cystine uptake even though the cystine defect in vivo was as high as 94% (ie, 6% reabsorption). In contrast, brush-border vesicles isolated from the kidney of a cystine stone-forming dog (Welsh Corgi) with a cystine defect of only 16% (ie, 84% reabsorption) had decreased uptake of cystine compared to values found for Beagle and Basenji vesicles. Thus, cystinuria found in Basenji dogs with the Fanconi syndrome differs from that in classic stone-forming cystinuric dogs. The alteration responsible for the cystinuria of Basenji dogs with Fanconi syndrome does not appear to have a membrane locus and may reflect altered energetics for transport, which are not detected in isolated vesicles. The cystine defect in cystinuric stone-forming dogs does appear to be reflected in the isolated membrane.

Membrane fluidity and sodium transport by renal membranes from dogs with spontaneous idiopathic Fanconi syndrome.

To comprehend the renal defect underlying the idiopathic Fanconi syndrome in the Basenji dog, we have used isolated renal brush border membrane vesicles to examine two factors that influence membrane nonelectrolyte transport processes, sodium flux and membrane fluidity. We have found that there is no significant difference in the rate of uptake of 100 mmol/L 22Na+ and conclude that the previously observed defects in the sodium gradient-stimulated overshoot of glucose and of proline are not related to an alteration in the flux of sodium at physiological concentrations. Since carrier proteins exist in a lipid milieu, alteration in the physical state of the lipid membrane can determine transport function. Renal brush border preparations from normal and affected animals were studied by measuring fluorescence polarization to assess differences in the physical state of the membranes using the fluorescent probe, DPH, which quantitates inner core membrane fluidity. Membranes from affected dogs consistently showed a higher fluidity as measured by eta, a parameter of DPH fluorescence polarization. Since membrane fluidity is related to lipid composition, the data suggest that there may be an important alteration in the lipids in renal membranes of affected animals.

Renal brush border membrane lipid composition in Basenji dogs with spontaneous idiopathic Fanconi syndrome.

To comprehend the renal defect underlying idiopathic Fanconi syndrome in the Basenji dog, we have focused on delineating the lipid profiles of renal brush border membranes isolated from affected and normal Basenji dogs to establish any physical or compositional changes underlying previously observed transport and membrane-fluidity changes. The lipid composition was studied with respect to total lipid, cholesterol, and phospholipid content, cholesterol to phospholipid ratio, distribution of the major phospholipid classes, and fatty acid composition. Total phospholipid of the isolated renal brush border membranes from Fanconi syndrome dogs analyzed by 31P nuclear magnetic resonance showed no difference compared with that of normal dogs. Examination of total fatty acids in both membranes using gas-liquid chromatography analysis of fatty acid methyl esters showed no difference in the mole percents of the major fatty acids. Our data suggest that changes in bulk membrane fluidity of the Fanconi syndrome dog renal brush border as measured by 1,6-diphenyl-1,3,5-hexatriene cannot be attributed to phospholipid and fatty acid compositional change. In the membranes isolated from affected dog kidney, the cholesterol content determined by gas-liquid chromatography analysis was 66 mol% higher than in membranes isolated from normal dog kidney. This correlates with the higher cholesterol to phospholipid molar ratio of 0.82 +/- 0.08 in the affected animal as compared with 0.58 +/- 0.04 in the normal. Cholesterol content and its microdomain in the membrane bilayer may be important in modulating transport functions. Increased membrane cholesterol content may affect the conformational motility of membrane transport proteins and thus affect their function.

Effects of bethanechol on canine urinary bladder smooth muscle function.

We studied whether the effects of bethanechol are mediated via a muscarinic receptor, the role of extracellular calcium on bladder contraction, and down-regulation of bladder contraction by bethanechol after activation with potassium chloride (KCl) and acetylcholine (Ach). Smooth muscle strips of normal urinary bladder were studied with standard methods to measure isometric force. Bethanechol caused a dose-dependent increase in bladder contraction. The potency of bethanechol is higher than Ach, as shown by higher peak active isometric stress (P(max)) and lower half-maximal contraction (ED(50)) (P< 0.01). The contractile responses to bethanechol were diminished in the presence of atropine, nifedipine and in calcium-free medium as shown by P(max) decreased by 58%, 87% and 65% and ED(50) increased by 314-, 24- and 16-fold, respectively. When bladder strips were stimulated with KCl and Ach, pre-treatment with bethanechol reduced the responses to KCl by 116-242% (P<0.05), while the contractile responses to Ach were unaltered. Thus, bethanechol induces bladder contraction via muscarinic receptor activation while both intracellular and extracellular calcium play a crucial role on bladder smooth muscle contraction. The mechanisms of down-regulation by bethanechol may be related to interference with calcium influx into the smooth muscle cells, rather than the desensitisation of muscarinic receptors or post-receptor steps of signal transduction following bethanechol binding to the receptor.

Comparison of direct and indirect (oscillometric) measurements of arterial blood pressure in conscious dogs.

Oscillometric measurements of arterial blood pressure were compared with direct measurements made on seven dogs fitted with catheters. Tail and limb cuff sites were used while the dogs were gently restrained either standing or in lateral recumbency. The accuracy of the readings for the various cuff sites was compared with the direct (gold standard) readings. The accuracy of the indirect readings was improved by using mean values from a series of readings rather than individual values and when the dogs were in lateral recumbency rather than standing. The differences between the direct and indirect values were greatest with high pressures, and with systolic rather than diastolic values. In standing dogs, the proximal forelimb readings (when obtainable) correlated most closely with the direct readings. The tail cuff readings correlated significantly with the direct readings, though less closely. The tail cuff readings were the most easily recorded in the standing dogs. In the laterally recumbent dogs, the readings from all the cuff sites correlated closely with the direct values except for diastolic readings from the distal hindlimb.

Norepinephrine kinetics in dogs with experimentally induced renal vascular hypertension.

OBJECTIVE: To determine norepinephrine (NE) kinetics in dogs with experimentally induced renal vascular hypertension. ANIMALS: 4 mixed-breed dogs. PROCEDURE: The study comprised a control and hypertensive period. The hypertensive period followed induction of renal vascular hypertension achieved by surgical placement of clips on both renal arteries to reduce diameter by approximately 80%. Arterial blood pressure, renal clearance, and NE kinetics were measured during each period while dogs were receiving a low-sodium diet. Measurements of NE kinetics and renal clearance during the hypertensive period were made 5 days after induction of hypertension. RESULTS: Five days after induction of hypertension, arterial blood pressure increased by 15 to 20 mm Hg. Mean (+/- SEM) plasma NE concentration and NE spillover rate increased significantly from 151.5+/-14.1 pg/ml and 8.03+/-0.62 ng/kg/min, respectively, during the control period to 631.4+/-30.5 pg/ml and 54.0+/-5.2 ng/kg/min, respectively, during the hypertensive period. Norepinephrine clearance rate also increased (54.0+/-2.4 vs. 86.0+/-9.3 ml/kg/min). Positive associations between mean arterial pressure (MAP) and NE concentration and spillover rate were detected. However, MAP and NE clearance rate were not associated. CONCLUSIONS AND CLINICAL RELEVANCE: Increased blood pressure during the hypertensive period was likely attributable to increased NE spillover rate, which resulted in a significant increase in plasma NE concentration. Analysis of these results suggests that central sympathetic outflow was increased and may be responsible for the pathogenesis of high blood pressure during the acute phase of renal vascular hypertension in dogs.

Postnatal development of renal tubular amino acid reabsorption in canine pups.

The renal clearance of amino acids in canine pups 5 days and 3, 8, and 12 weeks of age was studied. The 5-day-old pups had incomplete reabsorption of most amino acids. At 3 weeks, fractional reabsorption of 16 of 21 amino acids was complete; between 3 and 8 weeks, an adult pattern of reabsorption was present. Seemingly, a rapid development of amino acid transport precedes anatomic development or functional maturation of other transport systems.

Ureterocolonic anastomosis in clinically normal dogs.

Ureterocolonic anastomosis was evaluated in 13 clinically normal dogs. Urinary continence was maintained after surgery, and the procedure was completed without technique errors in all but 2 dogs. Three dogs died within 5 weeks (2 of undetermined causes and 1 of aspiration pneumonia and neurologic disease), and 1 dog was euthanatized 4 months after surgery because of neurologic signs. Two healthy dogs were euthanatized 3 months after surgery for light microscopic evaluation of their kidneys. Five dogs were euthanatized 6 months after surgery for light microscopic evaluation of their kidneys. Gastrointestinal and neurologic disturbances developed in 4 dogs at various postoperative intervals. Plasma ammonia concentration measured in 2 dogs with neurologic signs was increased. Plasma ammonia concentration measured in 5 dogs without neurologic signs was within normal limits. All 5 dogs, in which metabolic acidosis was diagnosed, had high normal or above normal serum chloride concentration. Serum urea nitrogen values were increased after surgery because of colonic absorption of urea. Serum creatinine concentration was increased in 1 dog 6 months after surgery. Individual kidney glomerular filtration rate was reduced in 38% (3/8) of the kidneys from 4 other dogs at 6 months after surgery. Of 5 dogs euthanatized at 3 to 4 months after surgery, 4 had bilateral pyelitis, and 1 had unilateral pyelonephritis. Six months after surgery, pyelonephritis was diagnosed in 40% (4/10) of the kidneys from 5 dogs. The ureterocolonic anastomosis procedure is a salvage procedure that should allow complete cystectomy. However, variable degrees of metabolic acidosis, hyperammonemia, and neurologic disease may result.

Cystinuria in a maned wolf.

A renal calculus composed principally of the amino acid, cystine, was found in an 8-year-old male maned wolf (Chrysocyon brachyurus). Cystine crystals were found in the urine sediment. The renal clearance of 10 amino acids was abnormal, whereas reabsorption of others was normal. The renal clearance of cystine, lysine, ornithine, and arginine exceeded the filtered load. The renal tubular handling of glucose, phosphate, sodium, potassium, and uric acid was identical to that for the clinically normal dog. These findings indicated an isolated renal tubular defect for cystine and other amino acids.

Clinical evaluation of glomerular function: 24-hour creatinine clearance in dogs.

Methods of renal clearance to measure glomerular filtration rate (GFR) were compared with plasma creatinine concentration in clinically normal and partially nephrectomized dogs. Glomerular filtration rate was measured by use of a simple 24-hour creatinine clearance method in 36 normal female Beagles. Mean values were 57.6 +/- 9.3 ml/minute/m2 of body surface or 3.7 +/- 0.77 ml/minute/kg of body weight. Variability of this measurement was considerable, as determined in 4 dogs studied on 4 consecutive days. Glomerular filtration rate was measured in the same 36 dogs while they were under anesthesia, using short clearance periods to compare inulin and endogenous creatinine clearance. Mean values for inulin were 41.8 +/- 13.9 ml/minute/m2 of body surface. A close agreement with creatinine clearance was found (correlation coefficient, 0.998). Mean plasma creatinine concentration was 0.82 (range, 0.5--1.0) mg/100 ml. The value of GFR measurement compared with plasma creatinine concentration was determined in 10 dogs after 75% nephrectomy. Sixty days after partial nephrectomy, GFR was reduced to 61% of normal. Mean plasma creatinine and blood urea nitrogen were 1.2 +/- 0.14 mg/100 ml and 20.4 +/- 7.1 mg/100 ml, respectively. Thus, the detection of reduced renal function may be uncertain when plasma creatinine or blood urea nitrogen are used as a means of evaluating renal function. It was concluded that a simple method of creatinine clearance is a sensitive and useful measurement to detect early or borderline reduction in glomerular function.

Characterization and treatment of acid-base and renal defects due to urethral obstruction in cats.

In 23 cats, urinary obstruction of 24 to 48 hours' duration caused marked azotemia, hyperphosphatemia, hyperkalemia, and metabolic acidosis. The metabolic acidosis was a consistent finding and was severe in all cats (venous pH, 7.11 +/- 0.09). Serum sodium and chloride were normal. Glycosuria was found in 17 (74%) of the cats. There was no clear difference in blood pH, serum chemical values, or electrolyte concentrations between cats obstructed 24 hours and those obstructed 48 hours or longer. At a mean of 8.4 hours after relief of obstruction, acid-base status was corrected to normal, using fluid replacement and sodium bicarbonate therapy. Blood urea nitrogen serum creatinine, and serum inorganic phosphorus improved significantly (P less than 0.01) at a mean of 19.5 hours after treatment. Variation in azotemia after fluid replacement suggested variable decreases in glomerular filtration rate after relief of obstruction. Hypokalemia occasionally developed after relief of obstruction during the postobstructive diuresis. It was concluded that fluid and electrolyte therapy must be regulated in response to the postobstructive diuresis, to ensure proper medical management.

Qualitative and quantitative analysis of uroliths in dogs: definitive determination of chemical type.

Effective treatment and prevention of urolithiasis depends on accurate determination of the chemical nature of the uroliths. A widely used qualitative chemical procedure was compared with quantitative crystallographic analysis of 272 canine uroliths. Agreement between the 2 methods was 78%. Qualitative analysis failed to detect 62% of calcium-containing uroliths and 83% of carbonate apatite uroliths. Qualitative analysis gave false-positive results for urates in 55% of cystine uroliths. Mixed uroliths comprising 6% of the total could not be classified without quantitative analysis. Silicate, cystine, and urate uroliths generally were of pure composition. Crystallographic analysis indicated the following distribution of major types: struvite, 69%; calcium oxalate, 10%; urate, 7%; silicate, 3.5%; cystine, 3.2%; calcium phosphate, 1%; and mixed, 6%. Among dogs with struvite uroliths, 66% had positive results of bacterial culturing from the urinary bladder. Six breeds (Miniature Schnauzer, Welsh Corgi, Lhasa Apso, Yorkshire Terrier, Pekingese, and Pug) had a significantly higher risk for urolithiasis, compared with other breeds. The German Shepherd Dog had a significantly lowered risk, compared with other breeds. Two breeds had significant relationship to a specific type of urolith: Miniature Schnauzer for oxalate, and Dalmatian for urate (P less than 0.001). It was concluded that quantitative analysis, using crystallography, was superior for the detection of calcium oxalate, carbonate apatite, cystine, urate, and mixed uroliths.

Inheritance of cystinuria and renal defect in Newfoundlands.

OBJECTIVE: To describe clinical features, characterize metabolic renal abnormalities, and evaluate mode of inheritance of cystinuria in Newfoundlands. DESIGN: Prospective study. ANIMALS: Two families of Newfoundlands including 11 dogs with dysuria, stranguria, or obstruction attributable to cystine calculi. PROCEDURE: Urinalysis and nitroprusside spot tests were performed to evaluate cystinuria in the affected dogs. All calculi were analyzed by crystallography. Amino acid concentrations in urine and plasma of affected dogs were compared with those in clinically normal related dogs. Renal fractional excretion and reabsorption of amino acids were determined in 5 affected Newfoundlands. RESULTS: Nine dogs had pure cystine calculi in the bladder, and 4 of these had renal cystine calculi. Affected dogs persistently excreted excessive amounts of cystine (> 500 nmol/mg of creatinine; reference = 54 +/- 38 nmol/mg of creatinine) and had typical cystine crystals in acidic urine. Urinary excretion of ornithine, lysine, and arginine was also high. Dogs with cystinuria had complete lack of reabsorption and active secretion of cystine, and reabsorption of lysine, ornithine, and arginine was moderately impaired. Although clinical signs of urinary obstruction were observed only in males, cystinuric male and female offspring were produced from noncystinuric parents, consistent with an autosomal recessive mode of inheritance. Obligate heterozygotes did not have clinical signs, and had normal urinary cystine content and renal amino acid reabsorption. CLINICAL IMPLICATIONS: Because detection of carriers by routine urinalysis is currently not possible, Newfoundlands with cystinuria and their parents and offspring should be excluded from breeding.