Abstract

Introduction

Increased activity of urinary N-acetyl-beta-D-glucosaminidase (NAG) indicates tubular cells injury and is used as the indicator of the renal function in humans and domestic animals.^1-4 The objective of this study was to evaluate validity of urinary NAG as the renal function indicator in cetaceans.

Materials and Methods

Between September 2009 and August 2011, urines of two female bottlenose dolphins (Tursiops truncatus) and one male pacific white-sided dolphin (Lagenorhynchus obliquidens) were collected. Kidney functions of all animals at that time were regarded normal as long as based on clinical histories, serum chemistries and urine analysis (chemistries, cytology and cultures). Urines of a female bottlenose dolphin with chronic kidney diseases (CKD) by nephrotic syndrome also were collected between September 2009 and July 2010. All animals were trained to voluntary urinate on land and their urines were collected almost aseptically. A urine sample of a dolphin with CKD was collected from the bladder during an autopsy. Urinary NAG activities of all urine samples were measured at a local human commercial laboratory within 24 h after collecting. The urine samples had been preserved in a refrigerator until submitting to the laboratory. Values of urinary NAG activity (U/L) corrected by urinary creatinine (g/L) were used as urinary NAG index (U/gCre). Urine strip tests and urine sediment analysis were simultaneously conducted to aliquots of all urine samples by aquarium stuffs.

Results and Discussion

Urinary NAG index of normal urine samples of female bottlenose dolphins were 3.0 ± 2.4 (mean ± SD) (n = 17) (Figure 1). Urinary NAG index of samples of a male pacific white-sided dolphin tended to become high values when sperms were appeared in urine sediments (Figure 2), NAG excreted from male reproductive organs was suspected as the reason. Urinary NAG index of a sample of a bottlenose dolphin with CKD was 9.9 before the onset of nephrotic syndrome, it was increased to the maximum 44.0 after the onset of the diseases, and decreased to the minimum 13.6 after glucocorticoid treatment. At the death with end-stage renal failure, it was reached to 236.9. In conclusion, measurements of urinary NAG seems to be useful to assess the renal function in cetaceans; however, results of male samples may have to be interpreted cautiously.

* Presenting author

Figure 1. Urinary NAG index in two female bottlenose dolphins Open circle shows actual results of each animal (A, B). Closed circle with bars shows the mean (closed circle) and standard deviation (bar).

Figure 2. Relationships of urinary NAG index and sperms appeared in urine sediments in a male pacific white-sided dolphin. Urine sediments were examined in more than 20 fields at 400 times magnification.

Literature Cited

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