Tissue distribution of radioactivity from ochratoxin A-14C in rats

Genomic analysis of Fisher F344 rat kidneys from a reproductive study following dietary ochratoxin A exposure

Ochratoxin A (OTA) is a mycotoxin produced by species of Penicillium and Aspergillus, and is found in many commodities including cereal grains, nuts, and coffee. OTA is a renal carcinogen and nephrotoxin at high concentrations, targeting the proximal tubules. This study uses transcriptomics and the previously reported apical data (Bondy et al., 2021) to infer mode-of-action of OTA toxicity in male and female rats exposed to low doses of OTA in utero and throughout development. Our findings support a male-specific activation of the innate and adaptive immune responses in F1 pups to OTA exposure. This was not found in the female F1 pups, and may be due to female-specific increased p38 activity and VDR signaling. Differentially expressed genes related to karyomegaly, MAPK activity, and immune activation appears to develop from in utero exposure to OTA whereas those related to decreased kidney and liver function, and changes to reproductive pathways occur in both rat generations. Together, these transcriptional results confirm that dietary exposure to OTA causes renal toxicity as well as alterations to hepatic and reproductive pathways in rats. In utero exposure of rats to OTA results in sex-specific alterations in immune response pathways, VDR signaling, and p38 activity.

Evidence for an enterohepatic circulation of ochratoxin A in mice

The distribution and elimination of [3H]ochratoxin A (OTA) from stomach content and tissue, intestine content and tissue, liver, bile, serum and urine of Swiss male mice which had received a single low dose of OTA by intubation was followed as a function of time. The profiles of radioactivity do not show a smooth decline after the absorption period, but an oscillating pattern with rapid declines followed by increases which favour the assumption of an enterohepatic circulation. Between 28% and 68% of conjugated OTA together with OTA cleavage products were found in bile giving evidence for biliary excretion of OTA and its metabolites in mice. When given i.m. to mice [3H]OTA is already found after 30 min in bile and intestine contents and its elimination patterns show several peaks confirming the biliary excretion and the enterohepatic circulation. Cholestyramine, which is known to prevent the enterohepatic circulation of drugs and toxins, changes the profile of elimination of OTA which no longer presents the cyclic pattern. This result is also in favour of an enterohepatic circulation of OTA. When phenylalanine is given together with OTA by oral gavage the toxicokinetics of the mycotoxin change completely in the different body fluids, in stomach and intestine content and tissues. Phenylalanine seems to facilitate the gastric absorption of OTA and the gastro-intestinal transit. It increases also its early excretion into urine and bile. However, its elimination pattern no longer shows the oscillating pattern. Thus phenylalanine seems to inhibit the intestinal reabsorption of OTA conjugates.

Placental transfer of ochratoxin A and its cytotoxic effect on the mouse embryonic brain

Pregnant ICR mice were given a single ip injection of 5 mg ochratoxin A/kg on day 11 or 13 of pregnancy. Concentrations of ochratoxin A in the maternal serum and tissues reached maximum levels within 2 hr of the injection and then decreased rapidly. The half-life of the toxin in serum was 28.7 hr on day 11 and 23.6 hr on day 13. On the other hand, the concentrations of ochratoxin A in the embryos were very low 2 hr after injection and then gradually increased up to 48 and 30 hr after injection on day 11 and 13, respectively. Pharmacokinetically, the embryo was found to be a 'deep' compartment. In mice treated with ochratoxin A on day 10 of pregnancy, the incidence of pyknotic cells in the telencephalon of the embryos began to increase 12 hr after injection to a peak between 36 and 48 hr, coinciding with the time of peak concentration of the toxin in the embryo.

Distribution of the [3H]-label from low doses of radioactive ochratoxin A ingested by rats, and evidence for DNA single-strand breaks caused in liver and kidneys

The distribution of a single low dose of [3H]-ochratoxin A (OTA) in different tissues of male Wistar rats, after administration by intubation, was investigated after 5 h, 24 h and 48 h. This dose corresponds to concentrations encountered in naturally contaminated feed (4 ppm). The distribution of [3H]-label varied with the time elapsed after administration; at 5 h the highest specific label was found in the stomach contents and in decreasing order in: intestinal contents, lung, liver, kidney, heart, fat, intestine, testes, and the lowest in muscles, spleen and brain. With exception of brain, fat, stomach and lung, all tissues showed maximum levels at 24 h, after which time the label decreased steadily, whereas in fat it increased. After a 12-week feeding experiment, with doses of 288.8 micrograms/kg corresponding to an intake of 4 ppm in feed each 48 h, the DNA in liver and kidneys was investigated for damage. By the alkaline elution method combined with micro-spectrofluorimetric determinations of DNA, evidence for DNA single-strand breaks was obtained. These findings support reports on the carcinogenic action of OTA.

Distribution of 14C-labelled ochratoxin A in pregnant mice

Autoradiography was used to study the distribution of 14C-labelled ochratoxin A for up to 4 hr after its iv administration to mice at various stages of pregnancy. The highest 14C concentration was consistently found in the bile throughout the experimental period. The concentration of radioactivity in the tissues was found, in decreasing order, in the liver, kidney, blood, salivary glands, large vessels, brown fat, myocardium, uterus and lymphatic tissues. The toxin was shown to cross the placental barrier on day 9 of pregnancy, at which time it is most effective in producing foetal malformations.