Two diets similar in caloric density and mineral content, but markedly different in protein content, were used to study the effects of dietary protein on renal function and morphologic and histopathologic changes in dogs that had functional renal tissue reduced by seven-eighths nephrectomy. The effects of moderate protein intake (MPrI = 15% protein; dry-matter basis) and high-protein intake (HPrI = 31% protein; dry-matter basis) were studied for the initial 7 months (period 1 [P1]) after renal mass reduction. Diets were then switched between groups during the following 7 months (period 2 [P2]) to evaluate the effects of increased or decreased protein intake. The HPrI caused significantly (P < 0.05) greater glomerular filtration rate (GFR) and renal growth than did MPrI during P1. Dogs that maintained HPrI during P1 and MPrI during P2 (group 1) had significant (P < 0.05) reduction in GFR during P2. Dogs that maintained MPrI during P1 and HPrI during P2 (group 2) had significant (P < 0.05) improvement in GFR and renal growth during P2. At the end of the study, renal reserve was evaluated in both groups of dogs before and after group 1 was returned to HPrI for 2 weeks. During this 2-week feeding trial, group-1 dogs had marked improvement in renal reserve, relative to group 2, and GFR increased to the terminal P1 values. Results indicate a possible residual benefit from HPrI during the early phase of compensatory renal growth in the form of functional compensatory memory to HPrI. The severity of renal lesions was indistinguishable between dogs of dietary groups during both study phases. Plasma electrolyte concentrations rapidly returned to normal range after renal ablation, but mild azotemia and proteinuria persisted throughout most of the study. High protein intake was not associated with increased degree or progression of proteinuria.

Excretion of creatinine, sodium sulfanilate (SS), and phenolsulfonphthalein (PSP) was studied in healthy goats. In conscious goats, mean (+/- SEM) inulin clearance was 2.26 +/- 0.08 ml/min/kg of body weight. Endogenous creatinine clearance, 1.97 +/- 0.09 ml/min/kg, underestimated inulin clearance (P < 0.01), probably because of the presence of noncreatinine chromogens in caprine plasma. The estimated renal clearance of PSP was 6.88 +/- 0.39 ml/min/kg, whereas the estimated renal clearance of SS was 3.71 +/- 0.39 ml/min/kg. Both exceeded inulin clearance (P < 0.01), confirming renal tubular secretion of both compounds. In 6 anesthetized goats, exogenous creatinine clearance and SS clearance exceeded inulin clearance (P < 0.05). Results of stop-flow experiments documented secretion of creatinine and ss by the peoximal portion of the caprine nephron. Plasma half-life of PSP in uninephrectomized goats exceeded that in intact goats (20.2 +/- 1.5 min vs 11.9 +/- 0.7 min; P < 0.01). Similarly, plasma half-life of SS was greater in goats after uninephrectomy (58.2 +/- 6.2 min vs 30.4 1.2 min; p < 0.01).

Pharmacokinetic variables of phenolsulfonphthalein (PSP) were determined in sheep after rapid IV injection and IV infusion to steady state. In Suffolk wethers, an average of < 75% of an IV administered dose was eliminated in urine, indicating that measures of systemic clearance overestimate renal clearance in this species. Furthermore, PSP elimination from plasma was more rapid in Suffolk than Rambouillet wethers and, in Suffolk ewes, systemic clearance decreased from mean +/- SD 7.8 +/- 0.3 ml/min/kg of body weight to 4.7 +/- 1.1 ml/min/kg at steady-state plasma concentration of 2.4 +/- 0.3 and 151.3 +/- 31.8 micrograms/ml, respectively. These observations indicate that, similar to that in other species, systemic clearance of PSP in sheep is concentration-dependent and that significant differences may exist between breeds.

Renal clearance procedures were performed on adult mixed-breed dogs with a wide range of renal function. Endogenous creatinine clearance was computed after analyzing plasma and urine for creatinine by use of 2 methods, PAP and kinetic Jaffe. For 20-minute clearance procedures, [14C]inulin clearance was measured simultaneously with endogenous creatinine clearance. For 111 twenty-minute clearance procedures performed on 24 dogs, [14C]inulin clearance was highly correlated with creatinine clearance for both methods of creatinine analysis (R2 = 0.979 for [14C]inulin-PAP; R2 = 0.943 for [14C]inulin-Jaffe). The absolute values for PAP and [14C]inulin clearance were nearly the same (PAP-to-[14C]inulin clearance ratio = 1.03 +/- 0.08), but those for Jaffe clearance were substantially less than those for [14C] inulin clearance Jaffe-to-[14C]inulin clearance ratio = 0.88 +/- 0.10). The Jaffe-to-[14C] inulin clearance ratio was inversely correlated with degree of renal function (R2 = 0.464), whereas the PAP-to-[14C]inulin clearance ratio was not correlated with degree of renal function (R2 = 0.060). Thus, Jaffe-determined creatinine clearance varied, in relation to [14C] inulin clearance, depending on degree of renal function. In 4 clinically normal dogs, 20-minute and 24-hour sample collections analyzed by use of the PAP method gave clearance values significantly greater, for both periods, than did Jaffe analyses. The PAP-determined creatinine clearance values were less than, but not significantly different from 20-minute exogenous creatinine clearance values determined 10 days after 24-hour collections. For 20-minute and 24-hour collections, the difference in clearance values between the PAP and Jaffe methods was attributable mostly to lower plasma creatinine values for the PAP method (mean +/- SEM, plasma PAP-to-Jaffe ratio = 0.798 +/- 0.053). However, urine creatinine values also were less by use of the PAP method.

During the fiscal year 1988, USDA-FSIS detected 3,095 antimicrobial violations in bob veal calves, using the calf antibiotic and sulfonamide test. Of the 3,095 carcass submissions involved, 945 were tested further to identify the causative agents. The results of tests on the available kidney, liver, and muscle specimens are reported. Kidney specimens yielded a specific agent most often (71.2%), with neomycin (42.6%) being cited most among agents found in kidneys. Neomycin was found less frequently in liver (4.5%) and muscle (0.2%). Among all tissues, unidentified microbial inhibitors were either the largest or second largest category found (kidney, 10.5%; liver, 27.1%; muscle, 7.8%), and no other agent exceeded 7.0% (streptomycin in kidney). The proportion of liver and muscle specimens that had unidentified microbial inhibitors is particularly important because the next most common classes were streptomycin in liver at 5.5% and sulfamethazine in muscle at 2%. The frequency of unidentified microbial inhibitors may justify the addition of tests to the FSIS battery for identification of agents. Not all tissues were tested for sulfonamides, hence these agents are likely to have been underreported. Less than 10% of the muscle specimens evaluated yielded an agent, suggesting most calf antibiotic and sulfonamide test-positive carcasses may have been safe with regard to residues in meat, although organs might have been adulterated. Specimens for verification were not selected completely randomly from the population of all calf antibiotic and sulfonamide test-positive animals and calves selected for testing were not chosen strictly by random sampling; therefore, extrapolation of the contents of this report to the bob veal calf industry must be done with caution.

Sonographic and anatomic observations were made of the kidneys of 23 Thoroughbreds or Standardbreds. In an in vitro study of 16 horses, precise correlations were established between the gross anatomic features of the kidneys and their sonographic appearance in images obtained in dorsal, sagittal, transverse, and transverse oblique anatomic planes. The renal cortex had a uniformly mottled echogenicity, and the renal medulla was relatively hypoechogenic, compared with the cortex. Acoustic anisotropy was observed in the cortex and medulla of the cranial and caudal extremities of each kidney. The distinctive renal pelvis was seen in the transverse plane as an echogenic pair of diverging lines that lead to the crescent shaped renal crest in the lateral half of the kidney. In images made in the sagittal plane, the renal pelvis was seen as a pair of parallel echogenic lines separated by the moderately echogenic line of the renal crest. The terminal recesses were best seen in the transverse oblique views of each extremity, where they appeared as moderately echogenic lines in the medulla of the cranial and caudal extremities. The interlobar vessels were represented as irregular echogenic lines in the medulla, and the arcuate vessels were seen as echogenic points at the corticomedullary junction. At the hilus, the renal artery or its branches was located cranial to the renal vein, which in turn was cranial to the position of the proximal portion of the ureter. In an in vivo study of 7 horses, sonographic images of the right kidney were obtained in the sagittal, transverse, and transverse oblique anatomic planes in all horses, with the transducer positioned at the 15th, 16th, or 17th intercostal space; images in the dorsal plane were obtained, however, in only 3 of the horses. For the left kidney, sonographic images were obtained in each of the anatomic planes when the transducer was positioned at the 16th or 17th intercostal space or the paralumbar fossa.

Three methods of determining glomerular filtration rate (GFR) were performed in adult ferrets, 9 months to 7 years old. Endogenous creatinine clearance was determined, using serum and urine creatinine values obtained during 24- and 48-hour collection periods from 27 ferrets housed in metabolic cages. Creatinine and radiolabeled inulin were administered to 12 female ferrets by constant IV infusion during isoflurane-induced anesthesia. Serial 20-minute urine collections, together with serum samples obtained at the midpoint of urine collection, provided measures for clearance calculations of these substances. Mean +/- SD endogenous creatinine clearance in ferrets for metabolic cage collections was 2.50 +/- 0.93 ml/min/ kg of body weight. There were no significant differences between the 24- and 48-hour clearance rates. Mean inulin clearance was 3.02 +/- 1.78, and mean exogenous creatinine clearance was 3.32 +/- 2.16 ml/ min/kg. Analysis of variance, using least-squared means adjustment, did not yield any significant differences between inulin and exogenous creatinine clearance rates. Exogenous creatinine clearance-to-inulin clearance ratio was 0.99 +/- 0.46, and there was significant correlation between the 2 methods (r = 0.82, P = 0.0001). Significant body temperature effects on inulin or exogenous creatinine clearance were not found. Infused inulin clearance, the generally preferred method for GFR calculation in mammalian species, was significantly (P = 0.0069) higher in younger (3.65 ml/min/kg) vs older ferrets (2.29 ml/min/kg). Results of this study indicate that inulin clearance is an adequate measure of GFR in ferrets as it is in other species. Compared with inulin clearance, exogenous creatinine clearance also provides a reliable estimate of GFR in ferrets.