Are mycotoxins risk factors for endemic nephropathy and associated urothelial cancers?

Evidence supporting a role of mycotoxin, in particular ochratoxin A (OA) and citrinin, in the etiology of Balkan endemic nephropathy (BEN) and associated urinary tract tumours (UTT) is reviewed. Both diseases occur in subjects born and/or living in certain rural areas where home-produced and home-stored stable foods were found to be more frequently contaminated by the OA and citrinin. OA levels in blood and urine from patients with BEN or UTT were higher than in controls. OA and possibly other mycotoxins cause endemic porcine nephropathy, a disease with morphology and clinical course similar to those of BEN. OA was carcinogenic in two rodent species with kidney as a major target organ. Animals and strains phenotype as fast metabolizers of debrisoquine were more susceptible to OA-induced carcinogenicity. Among BEN/UTT patients, a greater proportion of fast metabolizers was reported. Although no epidemiological proof of a direct causal role of mycotoxins in BEN/UTT etiology has been presented, the data accumulated so far indicate a need for prospective studies in which mycotoxins as well as other risk factors should be considered.

Citrinin mycotoxicosis in the rabbit: ultrastructural alterations.

Citrinin was given to rabbits as a single oral dose of 120 or 67 mg/kg. Rabbits were killed at 4, 6, 8, 10, and 12 hours post dosing, and the kidneys were fixed by intravascular perfusion. Ultrastructural alterations were evident by 4 hours after treatment. In the proximal tubule, alterations were brush border disruption, cytoplasmic rarefaction, and swelling of interdigitating processes. At higher doses, mitochondria were condensed and distorted. Medullary and straight cortical distal tubules had marked distention of the intercellular spaces and disorganization of interdigitating processes. Changes in cortical and outer medullary collecting ducts were similar but less severe. Renal alterations were suggestive of damage to membrane structure and/or transport functions and interference with cellular bioenergetics. Leukocytic infiltration was associated with damaged tubules indicating a contribution of inflammation to the development of the lesions.

Citrinin mycotoxicosis in the rabbit.

In three trials, single or multiple doses of citrinin dissolved in 0.5 N-NaOH and adjusted to neutral pH with HCl were given to rabbits by either the oral or intraperitoneal route. The 72-hr LD50 was 50 mg/kg body weight by intraperitoneal administration and 134 mg/kg by the oral route. The primary clinical sign in rabbits receiving a single oral dose of 125-150 mg citrinin/kg was fluid diarrhoea commencing 8 hr after dosing. Pathological alterations were generally confined to the kidney and consisted of degeneration and necrosis of proximal convoluted tubules and straight segments. In rabbits given a single oral dose of citrinin (130 mg/kg) the earliest histopathological change, seen 8 hr after dosing, was cytoplasmic vacuolation of tubular epithelial cells. Rabbits given a single oral dose of 120 mg citrinin/kg had regeneration of renal tubular epithelium accompanied by slight tubular cell necrosis when examined 7 days after dosing. Rabbits given multiple sublethal doses of citrinin (33.5 or 77 mg/kg daily for 7 days) had renal alterations of mild tubular degeneration and necrosis, and tubular regeneration.

Mycotoxicoses of animals.

Mycotoxicoses are intoxications caused by ingestions of foodstuffs contaminated with mycotoxins, i.e. toxic secondary metabolites of microscopic filamentous fungi (moulds). By field observations and by experimental testing, toxins or toxic strains of more than 100 species of fungi have been encountered. However, causal associations have so far only been established for a small number of mycotoxicoses in farm animals, and the more important mycotoxicoses are aflatoxicosis, facial eczema, mycotoxic nephropathy, and estrogenic syndrome. A full assessment of the impact of mycotoxins on the health of farm animals can hardly be made at present, because the amount of surveillance data from mycotoxicoses is very limited, due mainly to inadequate diagnostic criteria. A new set of criteria for the diagnosis of mycotoxicosis is proposed, which has been successfully applied in the causative study of mycotoxic porcine nephropathy.