Use of urinary renal biomarkers to evaluate the nephrotoxic effects of melamine or cyanuric acid in non-pregnant and pregnant rats.

Although traditional assessments of renal damage detect loss of kidney function, urinary renal biomarkers are proposed to indicate early changes in renal integrity. The recent adulteration of infant formula and other milk-based foods with melamine revealed a link between melamine ingestion and nephropathy. Thus, the effects of melamine and related analogs (e.g., cyanuric acid) should be assessed in other potentially sensitive groups. We evaluated whether urinary Kim-1, clusterin, and osteopontin could detect the effects of high doses of melamine or cyanuric acid in pregnant and non-pregnant female rats gavaged with 1000 mg/kg bw/day for 10 days. We demonstrate that these biomarkers can differentiate the severity of effects induced by melamine or cyanuric acid. All melamine-treated animals experienced adverse effects; however, pregnant rats were most sensitive as indicated by increased SCr, BUN, and kidney weights, decreased body weight, and presence of renal crystals. These effects coincided with elevated urinary biomarker levels as early as day 2 of exposure. One cyanuric acid-treated rat displayed effects similar to melamine, including increased urinary biomarker levels. This work illustrates that these biomarkers can detect early effects of melamine or cyanuric acid crystal-induced nephropathy and further supports the use of urinary protein immunoassays as a powerful, non-invasive method to assess nephrotoxicity.

Depletion of melamine and cyanuric acid in kidney of catfish Ictalurus punctatus and trout Oncorhynchus mykiss.

A risk assessment conducted in 2007 identified significant knowledge gaps about tissue residues of melamine and related triazine analogs such as cyanuric acid in animals that had eaten contaminated food. The USFDA subsequently designed studies to determine residue levels in muscle, serum, and kidneys of catfish and trout given a single gavage dose of 20 mg/kg body weight (BW) of melamine, cyanuric acid, or 20 mg/kg BW of both compounds simultaneously. Renal triazines were determined by LC-MS/MS at postdose days 1, 3, 7, 14, 28 (and day 42 for trout). When dosed individually, melamine and cyanuric acid kidney residues depleted much faster than those in fish given both compounds together. Combined dose residue depletion was punctuated by extreme outliers due to the formation of persistent renal melamine cyanurate crystals.

Renal crystal formation after combined or sequential oral administration of melamine and cyanuric acid.

We evaluated renal melamine-cyanurate crystal spherulite formation after single and repeated ingestion of both melamine (MEL) and cyanuric acid (CYA) in catfish and trout. MEL and CYA were co-administered orally over a range of doses, 0.1-20mg/kg body weight (bw) of each compound, either once or repeatedly for 4, 14 or 28 days (d). In catfish, the No Observable Adverse Effects Levels (NOAELs) for crystal formation for single, 4d or 14 d dosing were 10, 2.5 and 0.5mg/kg bw, respectively. In trout, the respective NOAELs were 2.5, 2.5 and 0.5mg/kg bw. No renal crystals formed in catfish fed 0.1mg/kg bw of each compound for 28 d. Sequential administration of 20mg/kg bw of MEL followed by 20mg/kg bw of CYA or vise-versa, with waiting periods of 1, 3, 7, 14 or 21 d between compound dosing also induced renal crystal formation in fish. These studies show that both catfish and trout are sensitive, non-mammalian models, for renal crystal formation following MEL and CYA ingestion. Since fish generally excrete chemicals more slowly than mammals, they may provide a "worst case scenario" model for higher risk populations, such as infants or persons with compromised renal function.

Mycobacteria isolated from Chesapeake Bay fish.

Mycobacteriosis in fish can result in ulcers, emaciation, and in some cases death. Mycobacteria have been previously isolated from a variety of Chesapeake Bay fish species, and the current study was designed to identify potential host specificity and location fidelity of mycobacterial isolates. Mycobacteria were isolated from wild fish of the Chesapeake Bay collected from the Upper Bay, the Choptank River, Herring Bay, the Chicamacomico River, the Pocomoke River and the Potomac River in 2003-2006. Mycobacterial isolates were recovered from striped bass, Morone saxatilis, Atlantic menhaden, Brevoortia tyrannus, white perch, Morone americana, summer flounder, Paralichthys dentatus, spot, Leiostomus xanthurus, largemouth bass, Micropterus salmoides, channel catfish, Ictalurus punctatus, common carp, Cyprinus carpio carpio, spotted seatrout, Cynoscion nebulosus, killifish, Fundulus sp., blueback herring, Alosa aestivalis, American gizzard shad, Dorosoma cepedianum and American silver perch, Bairdiella chrysoura. Twenty-nine well-defined mycobacterial groups resulted from gas chromatography dendrogram clustering of isolates. The majority of groups included more than one host species and more than one site of collection. However, four groups contained only striped bass isolates, three of which were similar to M. shottsii. Therefore, multiple Chesapeake Bay fish species are colonized with multiple mycobacterial isolates, of which few appear to be host or location specific.

A review of mycobacteriosis in marine fish.

Mycobacteriosis is a serious and often lethal disease of fish, affecting a wide range of species globally both in culture and wild settings. Caused by several species of the genus Mycobacterium, the disease has received considerable attention in recent years because of the discovery of new species in piscine hosts, epizootics in wild fisheries, and the ability of a few species to infect humans. The impact of this disease in aquaculture and the aquaria trade has been well reported and there is currently no widely accepted cure other than depopulation and facility disinfection. However, the impact on wild fisheries is poorly understood and may relate to species-specific interactions (host-pathogen) and possibly environmental stressors. In this review, much of what is known about mycobacteriosis in marine fish is summarized with particular attention to an epizootic in striped bass, Morone saxatilis, (Walbaum), in Chesapeake Bay, USA.