The ochratoxina comprise a group of closely related derivatives of dihydro-isocoumarins linked to phenylalanine. Seven ochratoxins have been isolated from fungal cultures under laboratory conditions. In contrast, only ochratoxin A (OA) and, in a few instances, ochratoxin B, have been encountered ae natural contaminants of produce, cereals in particular. The reported frequency of OA contamination in produce varies from 0 .4-14.2% in marketed cereals, and up to 57 .6% in feed cereals collected on farms. The levels range from 5 to 27,500 ug/kg (Review: KROCH, 1978). The fungal producers of OA, isolated mainly from postharvest samples, include seven species from the Aspergillus ochraceus group, and six Penicillium species, with P. viridicatum as the predominant producer. Maximal OA production by P. viridicatum occurs at a temperature of 24Ã¸C and a water activity (aw) of 0.95, but OA production is still possible at 4Ã¸C ; then however at aw 0.99 (NORTHOLT et al ., 1979) . Also the preharvest mycoflora of cereals (barley) includes OA-producers, with P. purpurrescens as the predominant producer (LILLEHOJ et al ., 1979). OA occurs as tissue residues in food animals (pig, poultry) exposed to OA-contaminated; levels up to 100 ug/kg have been encountered. Under experimental conditions OA has revealed pronounced nephrotoxic effects, by peroral administration, in all single-stomach animals investigated, including rat, guinea pig, dog, pig, birds. The proximal tubule is the initial target segment of the nephron. Long term exposure (2 years) of pigs to 1 mg OA/kg feed resulted in progressive nephropathy, although no terminal renal failure was reached (KROCH et al ., 1979). Teratogenic effects have been induced in the mouse, hamster and rat by exposure to 1-20 mg OA/kg feed (KANISAWA and SUZUKI, 1978). The effect of OA on a subcellular level includes inhibition of intramitochondrial phosphate transport resulting in deterioration of the mitochondria (MEISNER, 1976). OA is a major disease determinant of porcine nephropathy, although also other mycotoxins, such as citrinin, may be causally involved (KROCH, 1978). This disease is endemic in Denmark, with epidemics occurring following excessive climatic conditions. Porcine nephropathy has been reported from Sweden associated with ingestion of OA-contaminated feed (RUTQVIST et al., 1978). Balkan endemic nephropathy is a renal disease in humans, comparable with OA induced porcine nephropathy (KROCH, 1974). Prevalence rates of this disease are influenced by climatic conditions favoring mycotoxin production (AUSTWICK and SMITH, 1974). High frequencies of OA contamination of foodstuffs were encountered in an area with endemic nephropathy in Yugoslavia, indicating elevated OA exposure of the population (KROCH et .al ., 1977).
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