Serum urate concentrations in the Dalmatian Coach Hound

The mean concentration of urate in the serum of 80 Dalmatian Coach Hounds was approximately double that in the serum of 99 dogs of other breeds. Both values were higher than those reported previously.     

Autoregulation of superficial nephron function in the alloperfused dog kidney

Isolated dog kidneys were each pumpperfused by another dog during 4 experimental periods at perfusion pressures (PP) of 21, 17, 13, and 8 kPa, resp. (i. e. 160, 130, 95, and 60 mm Hg). At the 3 highest PP values, the total kidney renal blood flow (RBF) and glomerular filtration rate (GFR) were perfectly autoregulated while at the lowest value both values were significantly lowered. No significant difference was observed between the single nephron GFR (SNGFR) of periods 1 and 2; in period 3 (PP=13 kPa) a lower value was observed (P<0.05). Free flow pressure in proximal convolution (FFP), stop-flow pressure (SFP), and peritubular capillary pressure (PCP) were not different in period 2 than in period 1, but were significantly lower in period 3 (P=0.02–0.05). Effective filatration pressure (EFP) was the highest in period 1, decreasing significantly with decreasing PP. Filtration pressure equilibrium was observed in period 4 at PP 8 kPa. Total blood flow resistance (R_T) fell with decreasing PP, the drop being due to a steep decline in afferent resistance (R_A). Efferent resistance (R_E) increased as PP decreased. Ultrafiltration coefficient (K_f) rose with declining PP both within and outside the autoregulatory range. The results indicate that the lower limit of autoregulation is higher in superficial nephrons than in the whole kidney.     

Characteristics of urate influx in the rat nephron.

Permeability of the tubular epithelium to urate presented on the peritubular side was studied in anesthetized rats during mannitol diuresis by capillary microinjections of [14C]urate and [3H]inulin, [14C]PAH and [3H]inulin, or [14C]urate and [3H]PAH. Recovery of isotopes was determined in urine collected serially from the injected and contralateral kidney. Appearance and peak excretion of urate in the experimental but not in the contralateral kidney preceded inulin and coincided with PAH, indicating proximal permeability to urate. Recovery of urate was higher from the injected than from the contralateral kidney. Urate precession and recovery did not change after addition of PAH (1.5-6.4 mm) to [14C]urate-[3H]inulin solutions, whereas they decreased significantly in the experimental kidney after pyrazinoate (1.6-3.2 mM) addition. On the other hand, no effect of urate on [14C]PAH-[3H]inulin injections was detectable. These findings are suggestive of a carrier-mediated transtubular influx of urate in rat proximal tubule. Absence of competition with PAH may suggest differences in the secretory mechanisms for organic acids.     

Inner ear structure in the deaf and normally hearing Dalmatian dog

Both cochleae of two 6-week-old Dalmatian dogs of the same litter were examined by means of surface specimens and histological section techniques. Basic quantitative data on the morphometry of the cochlear duct in the hearing (though hypopigmented) pup are presented. The cochlear ducts of the deaf (though normally coloured) pup exhibited in general the same alterations (collapse of the scala media) as described in the literature. In addition, we describe also the coalescence of membranous structures, projection of the tectorial membrane up to the spiral ligament and preservation of inner hair cells in the second (i.e. middle) cochlear coil. These new findings complement the previous data and indicate an alternative possible course of hereditary inner ear degeneration in the Dalmatian dog.     

Renal urate transport during variations in urate synthesis in the rat

Summary In order to determine the effect of intrarenal synthesis of urate upon the urinary urate excretion in the rat, we effected large changes in urate synthesis by increasing it with hypoxanthine and decreasing it with allopurinol. Hypoxanthine infusion increased plasma urate rapidly and also increased the urinary urate excretion and its renal clearance. However, when the plasma urate was maintained constant, hypoxanthine had no effect upon renal urate transport. Conversely, allopurinol infusion rapidly diminished the plasma urate, urinary urate excretion and its renal clearance. Again, the maintenance of a constant plasma urate concentration prevented any change in urate transport during allopurinol. The urinary degradative purine metabolite pattern was altered pre-dictably by hypoxanthine and allopurinol. Assuming that any putative intrarenal component of urate synthesis would be affected predictably and consistently by hypoxanthine and allopurinol, these results suggest that changes in intrarenal urate synthesis are not an important determinant of urate excretion in the rat.Reported in abstract form in Clinical Research23, 508 A (1975)