Dietary effects on urinary physicochemistry in Navy bottlenose dolphins (Tursiops truncatus) for the prevention of ammonium urate kidney stones.

Bottlenose dolphins are susceptible to developing ammonium urate (NH4U) kidney stones. The current study was designed to test the hypothesis that diet influences the urinary physicochemistry risk factors associated with nephrolithiasis in dolphins. A comprehensive nutrient analysis was performed revealing that the baseline diet (BD) commonly fed to dolphins under professional care had a greater purine content and a more negative dietary cation-anion difference (DCAD) when compared with a model diet consumed by free-ranging dolphins. A modified diet (MD) was formulated to include free-ranging diet fish species and achieve a more positive DCAD. The BD had a more negative DCAD (-52 mEq/Mcal metabolizable energy) when compared with the MD (+51 mEq/Mcal ME), which more closely approximated the DCAD of the free-ranging model diet (+152 mEq/Mcal ME). Six dolphins (with stones) were fed the BD followed by the MD for a minimum of 4 wk. At the end of each feeding trial, a 6-h continuous urine collection was performed to compare urine parameters of dolphins fed the BD versus MD. Dolphins consuming the MD demonstrated a significant decrease in urinary ammonium, net acid excretion, saturation index of ammonium urate, and phosphorous, and a significant increase in urinary citrate and net gastrointestinal (GI) alkali absorption, as compared with urine parameters assessed when fed the BD. Increasing the proportion of free-ranging diet fish species and optimizing the DCAD positively influenced some of the risk factors believed to be associated with NH4U kidney stone development in bottlenose dolphins under professional care.

Comparison of potential dietary and urinary risk factors for ammonium urate nephrolithiasis in two bottlenose dolphin ( Tursiops truncatus) populations.

Dietary and urinary risk factors have been implicated in conditions favoring ammonium urate nephrolithiasis in managed dolphins compared with free-ranging dolphins. In this study, urine samples were collected from 16 dolphins (8 cases, 8 controls) from the U.S. Navy Marine Mammal Program for the purposes of assessing changes in urinary biomarkers after a large meal. Urinary biomarkers and nephrolithiasis presence were assessed opportunistically in 15 long-term resident free-ranging dolphins living in Sarasota Bay, Florida. Additionally, the total purine contents of fish commonly consumed by each dolphin population were measured to evaluate potential dietary risk factors. Populations were compared for total dietary purine composition, recently fed status, nephrolithiasis presence, and differences in urinary biochemical, acid-base, and physicochemical parameters via Wilcoxon rank sum analysis and least square means. Managed dolphins had higher urinary pH and ammonium ([Formula: see text]) in both pre- and postprandial conditions and higher urinary uric acid and saturation indices of NH4U in the postprandial condition compared with free-ranging dolphins ( P < 0.05). The purine content was greater ( P < 0.0001) in the diet consumed by managed dolphins [7 mmol/Mcal metabolizable energy (ME)] than in the free-ranging dolphin diet (4 mmol/Mcal ME). Free-ranging dolphins did not show evidence of nephrolithiasis. Observed differences in urinary biomarkers and dietary purine content in these two dolphin populations suggest a pathophysiologic basis for the role of fish types on the risk of NH4U stone formation. Future research should investigate fish type and feeding frequency, inhibitors and promoters, and alkalinizing therapy for reducing NH4U nephrolithiasis in dolphins.

Solubility of ammonium acid urate nephroliths from bottlenose dolphins (Tursiops truncatus).

Nephrolithiasis has been identified in managed populations of bottlenose dolphins (Tursiops truncatus); most of these nephroliths are composed of 100% ammonium acid urate (AAU). Several therapies are being investigated to treat and prevent nephrolithiasis in dolphins including the alkalization of urine for dissolution of nephroliths. This study evaluates the solubility of AAU nephroliths in a phosphate buffer, pH range 6.0-8.0, and in a carbonate-bicarbonate buffer, pH range 9.0-10.8. AAU nephroliths were obtained from six dolphins and solubility studies were conducted using reverse-phase high performance liquid chromatography with ultraviolet detection at 290 nm. AAU nephroliths were much more soluble in a carbonate-bicarbonate buffer, pH range 9.0-10.8 compared to phosphate buffer pH range 6.0-8.0. In the pH range 6.0-8.0, the solubility was 45% lower in potassium phosphate buffer compared to sodium phosphate buffer. When citrate was used along with phosphate in the same pH range, the solubility was improved by 13%. At pH 7 and pH 8, 150 mM ionic strength buffer was optimum for dissolution. In summary, adjustment of urinary pH alone does not appear to be a useful way to treat AAU stones in bottlenose dolphins. Better understanding of the pathophysiology of AAU nephrolithiasis in dolphins is needed to optimize kidney stone prevention and treatment.

Sentinels of synthetics - a comparison of phthalate exposure between common bottlenose dolphins (Tursiops truncatus) and human reference populations.

Phthalates are chemical esters used as additives in common consumer goods, such as plastics, household cleaners, and personal care products. Phthalates are not chemically bound to the items to which they are added and can easily leach into the surrounding environment. Anthropogenic drivers, such as coastal plastic pollution and wastewater runoff, increase the exposure potential for coastal marine fauna. Phthalate exposure in free-ranging bottlenose dolphins has been the focus of recent study, with indications of heightened exposure to certain phthalate compounds. The objective of this study was to compare urinary phthalate metabolite concentrations among bottlenose dolphins (Tursiops truncatus) sampled in Sarasota Bay, FL, to levels reported in human samples collected as part of the Centers for Disease Control and Prevention's (CDC) National Health and Nutrition Examination Survey (NHANES). Monoethyl phthalate (MEP) and mono-(2-ethylhexyl) phthalate (MEHP) were the most prevalent metabolites detected in dolphin urine (n = 51; MEP = 29.41%; MEHP = 54.90%). The geometric mean (GM) concentration of MEP was significantly lower for dolphins (GM = 4.51 ng/mL; 95% CI: 2.77-7.34 ng/mL) compared to humans (p<0.05), while dolphin concentrations of MEHP (GM = 4.57 ng/mL; 95% CI: 2.37-8.80 ng/mL) were significantly higher than levels reported in NHANES (p<0.05). Health impacts to bottlenose dolphins resulting from elevated exposure to the MEHP parent compound (diethyl-2-ethylhexyl phthalate, DEHP) are currently unknown. However, given the evidence of endocrine disruption, reproductive impairment, and abnormal development in humans, pursuing investigations of potential health effects in exposed bottlenose dolphins would be warranted.

Baseline urinalysis values in common bottlenose dolphins under human care in the Caribbean.

Urinalysis is a rapid, simple, inexpensive, and reliable test that documents urine abnormalities reflecting various types of renal, hormonal, or metabolic diseases. Urinalysis could assist proper monitoring of the health of dolphins under human care; however, normal baseline values for dolphin urinalysis have not been reported, to our knowledge. We sampled urine from 193 common bottlenose dolphins ( Tursiops truncatus), living under human care in 24 Caribbean dolphinariums, by voluntary free-catch and analyzed the urine for chemical and microscopic variables using multi-agent dry reagent chemistry dipstick test strips, dedicated pH reagent strips, and unstained sediment slides. Most urine was clear, pale yellow to dark yellow, and had a fishy odor. Dipstick glucose, bilirubin, ketones, and nitrites were negative in all dolphins. The urine pH was acidic ( x¯ ± SD; 5.88 ± 0.58) and specific gravity (SG) was 1.035 ± 0.008. Most animals had 0-2 red blood cells and white blood cells per 40× field, and were negative for proteins. On microscopic sediment, 42.7% of samples had few-to-many squamous epithelial cells; hyaline and epithelial casts were observed only rarely. Crystals were observed in 36.6% of the samples; most were calcium oxalate dihydrate (48.2%) and amorphous urates (42.4%). The values obtained in our study can be used as a reference for health monitoring of dolphins in dolphinariums, and to monitor renal conditions and function in dolphins being rehabilitated or under human care.

Concurrent exposure of bottlenose dolphins (Tursiops truncatus) to multiple algal toxins in Sarasota Bay, Florida, USA.

Sentinel species such as bottlenose dolphins (Tursiops truncatus) can be impacted by large-scale mortality events due to exposure to marine algal toxins. In the Sarasota Bay region (Gulf of Mexico, Florida, USA), the bottlenose dolphin population is frequently exposed to harmful algal blooms (HABs) of Karenia brevis and the neurotoxic brevetoxins (PbTx; BTX) produced by this dinoflagellate. Live dolphins sampled during capture-release health assessments performed in this region tested positive for two HAB toxins; brevetoxin and domoic acid (DA). Over a ten-year study period (2000-2009) we have determined that bottlenose dolphins are exposed to brevetoxin and/or DA on a nearly annual basis (i.e., DA: 2004, 2005, 2006, 2008, 2009; brevetoxin: 2000, 2004, 2005, 2008, 2009) with 36% of all animals testing positive for brevetoxin (n = 118) and 53% positive for DA (n = 83) with several individuals (14%) testing positive for both neurotoxins in at least one tissue/fluid. To date there have been no previously published reports of DA in southwestern Florida marine mammals, however the May 2008 health assessment coincided with a Pseudo-nitzschia pseudodelicatissima bloom that was the likely source of DA observed in seawater and live dolphin samples. Concurrently, both DA and brevetoxin were observed in common prey fish. Although no Pseudo-nitzschia bloom was identified the following year, DA was identified in seawater, fish, sediment, snails, and dolphins. DA concentrations in feces were positively correlated with hematologic parameters including an increase in total white blood cell (p = 0.001) and eosinophil (p<0.001) counts. Our findings demonstrate that dolphins within Sarasota Bay are commonly exposed to two algal toxins, and provide the impetus to further explore the potential long-term impacts on bottlenose dolphin health.

Effects of fresh and seawater ingestion on osmoregulation in Atlantic bottlenose dolphins (Tursiops truncatus).

Bottlenose dolphins (Tursiops truncatus) are marine mammals with body water needs challenged by little access to fresh water and constant exposure to salt water. Osmoregulation has been studied in marine mammals for a century. Research assessing the effects of ingested fresh water or seawater in dolphins, however, has been limited to few animals and sampling times. Nine 16- to 25-h studies were conducted on eight adult dolphins to assess the hourly impact of fresh water, seawater, and seawater with protein ingestion on plasma and urine osmolality, urine flow rate (ufr), urinary and plasma solute concentrations, and solute clearance rates. Fresh water ingestion increased ufr. Fresh water ingestion also decreased plasma and urine osmolality, sodium and chloride urine concentrations, and solute excretion rates. Seawater ingestion resulted in increased ufr, sodium, chloride, and potassium urine concentrations, sodium excretion rates, and urine osmolality. Seawater with protein ingestion was associated with increased ufr, plasma osmolality, sodium excretion, and sodium, chloride, potassium, and urea urine concentrations. In conclusion, bottlenose dolphins appear to maintain water and plasma solute balance after ingesting fresh water or seawater by altering urine osmolality and solute clearance. Ingestion of protein with seawater appears to further push osmoregulation limits and urine solute concentrations in dolphins.

Hypocitraturia in common bottlenose dolphins (Tursiops truncatus): assessing a potential risk factor for urate nephrolithiasis.

Numerous cases of urate nephrolithiasis in managed collections of common bottlenose dolphins (Tursiops truncatus) have been reported, but nephrolithiasis is believed to be uncommon in wild dolphins. Risk factors for urate nephrolithiasis in humans include low urinary pH and hypocitraturia. Urine samples from 94 dolphins were collected during April 2006 through June 2009 from 4 wild populations (n = 62) and 4 managed collections (n = 32). In addition, urine uric acid and pH were tested in a subset of these animals. Our null hypothesis was that wild and managed collection dolphins would have no significant differences in urinary creatinine, citrate, and uric acid concentrations and pH. Among urine samples from all 94 dolphins, the urinary levels (mean +/- SEM) for creatinine, citrate, uric acid, and pH were 139 +/- 7.6 mg/dL, 100 +/- 20 mg citrate/g creatinine, 305 +/- 32 mg uric acid/g creatinine, and 6.2 +/- 0.05, respectively. Of the 4 urinary variables, only citrate concentration varied significantly between the 2 primary study groups; compared with wild dolphins, managed collection dolphins were more likely to have undetectable levels of citrate in the urine (21.0% and 81.3%, respectively). Mean urinary citrate concentrations for managed collection and wild dolphin populations were 2 and 150 mg citrate/g creatinine, respectively. We conclude that some managed collections of dolphins, like humans, may be predisposed to urate nephrolithiasis due to the presence of hypocitraturia. Subsequent investigations can include associations between metabolic syndrome, hypocitraturia, and urate nephrolithiasis in humans and dolphins; and the impact of varying levels of seawater ingestion on citrate excretion.

Localization of aquaporin-2, renal morphology and urine composition in the bottlenose dolphin and the Baird's beaked whale.

This study examined the distribution pattern of aquaporin-2 (AQP2), relative medullary thickness (RMT) and urine properties in the bottlenose dolphin Tursiops truncatus and Baird's beaked whale Berardius bairdii. Immunohistochemical studies revealed that AQP2 was localized in the collecting tubules/ducts of both species' renicules, as in terrestrial mammals. The collecting ducts with AQP2 were thinner and arranged more densely in the dolphin than in the whale. RMT values in the renicule were moderate in both species, but were significantly higher in the dolphin (6.0 +/- 0.9) than the whale (4.9 +/- 0.7). Urine of the bottlenose dolphin is comparatively concentrated (osmolality: 1715.7 +/- 279.4 mOsm kg(-1), Na(+): 490.1 +/- 87.9 mmol l(-1), Cl(-): 402.7 +/- 79.6 mmol l(-1), K(+): 80.7 +/- 25.8 mmol l(-1), urea nitrogen: 703.5 +/- 253.9 mmol l(-1)), while urine of the dead Baird's beaked whale is less concentrated (osmolality: 837.5 +/- 293.8 mOsm kg(-1), Na(+): 192.9 +/- 81.5 mmol l(-1), Cl(-): 159.9 +/- 71.4 mmol l(-1), K(+): 44.3 +/- 29.5 mmol l(-1), urea nitrogen: 270.7 +/- 120.3 mmol l(-1)). These data suggest it is possible that the differences in these renal morphological features may be related in some way to the difference in urine composition between the species, although further studies are necessary.