Assessment of novel avian renal disease markers for the detection of experimental nephrotoxicosis in pigeons (Columba livia).

Renal disease is a major cause of illness in captive and wild avian species. Current renal disease markers (e.g., uric acid, blood urea nitrogen, and creatinine) are insensitive. Two endogenous markers, creatine and N-acetyl-beta-D-glucosaminidase (NAG), were selected for study in the pigeon (Columba livia). Representative organs from four pigeons were surveyed to determine those exhibiting the highest level of each marker. In a separate study, NAG and creatine from plasma and urine were assayed before and after gentamicin (50 mg/kg twice daily), administration for up to 9 days. Observer-blinded pathologic scoring (five saline solution controls, 17 treated birds) was used to verify the presence of renal disease that corresponded to marker increases. The first study revealed that kidney tissue had the highest NAG activity (by approximately six times), and pectoral muscle had the most creatine (>900 times). In response to gentamicin, plasma creatine (>five times) and NAG increased (approximately six times), which paralleled uric acid (>10 times). Urine creatine (approximately 60 times) and NAG increased dramatically (approximately 50 times) in response to gentamicin. In conclusion, NAG, especially in the urine, may be of value to noninvasively detect renal toxin exposures and to monitor potentially nephrotoxic drugs, and might be of value to screen free-ranging birds in large exhibits or in the wild by assaying fresh urate samples at feeding stations.

Development of amoxicillin enzyme-linked immunosorbent assay and measurements of tissue amoxicillin concentrations in a pigeon microdialysis model.

A sensitive ELISA was developed for the detection of amoxicillin (AMX) in serum, urine, and milk. The ELISA used an indirect competitive method produced by coating the plate with ovalbumin conjugated with AMX hapten. Antibodies against AMX-BSA were detected by a goat-antirabbit antibody conjugated with peroxidase. Calibration standard curves ranged from 1.28 ng/mL to 20 microg/mL [IC(50) (inhibition concentration 50%) = 100 ng/mL], and the limits of detection were 1.3, 2.7, and 4.8 ng/mL for urine, milk, and serum, respectively. The intra- and interassay variations were less than 4 and 9.6%. The antibody produced against AMX cross-reacted highly with penicillin G (77%); cross-reacted moderately with ampicillin, oxacillin, and cloxacillin (56.9, 51.4, and 48.8%, respectively); but was considered non-cross-reactive with dicloxacillin (7.4%), cefadroxil (<1%), and cefazolin (<1%). Concentrations of AMX were measured simultaneously in venous blood and muscles by using the developed AMX ELISA in an in vivo microdialysis model designed for pigeons. Following i.m. injection (25 mg/kg), AMX attained a peak blood level of 4.74 +/-0.30 mu g/mL and decreased with a half-life of 2.38 +/-0.16 h. In contrast, measurements in pectoral and femoral muscles exhibited delayed appearances, reduced peak concentrations, and prolonged half-lives of 4.07 +/-0.48 (pectoral) and 3.01 +/-0.26 (femoral) that were significantly different from each other and those in the blood (P < 0.05). Blood protein binding was calculated to be 27.9 +/-5.7%. This study demonstrated the semiquantitative application of a selective AMX ELISA in the first microdialysis procedure for continuous monitoring of drug levels in specific tissues of pigeons and maybe useful for related studies in other poultry species.

Drinking and renal responses to peripherally administered osmotic stimuli in the pigeon (Columbia livia).

Pigeons drank copiously in response to intravenous (I.V.) infusion of approximately equi-osmolar hypertonic solutions of NaCl (0.5 M), sucrose (1.0 M) or mannitol (1.0 M). I.V. infusions of hypertonic glucose (1.0 M) or urea (1.0 M) were less effective in causing drinking. The calculated percentage change in plasma osmolality at the onset of drinking was similar for the three hypertonic solutions, NaCl, sucrose and mannitol, irrespective of the concentration of the solution infused. A greater volume of water was drunk in response to I.V. infusion of 7 ml of 1.0 M-sucrose than in response to a similar volume of 1.0 M-NaCl or mannitol. This appeared to be in response to the large diuresis caused by sucrose infusions. Excretion of the osmotic load was more rapid following I.V. hypertonic sucrose and mannitol than following hypertonic NaCl, glucose or urea in the 10 h of the experiment. In anaesthetized pigeons, I.V. infusion of hypertonic NaCl (0.5 M), sucrose (1.0 M) or urea (1.0 M) caused similar increases in plasma osmolality. The haematocrit was significantly reduced after NaCl or sucrose but not after urea. Plasma Na+ concentration was significantly increased after NaCl, and decreased after sucrose, whereas urea produced little change. Following I.V. hypertonic NaCl or urea, the Na+ concentration of the cerebrospinal fluid (c.s.f.) was increased and its flow reduced compared with isotonic NaCl infusions. Hypertonic sucrose stopped the flow of c.s.f. almost completely during the course of the experiment. These experiments suggest that the drinking and renal responses of pigeons following osmotic stimuli are similar to those of mammals and that they appear to retain Na+.