Abnormal ethanol metabolism in Long-Evans Cinnamon rats, a mutant strain developing spontaneous hepatoma

Mechanisms of umami taste preference and aversion in rats

The influence of glutamate intake on growth and appetite, and the mechanisms of preference and aversion for monosodium L-glutamate (MSG) solutions were investigated in rats. Food intake, but not weight gain, was reduced significantly in rats fed a glutamate + glutamine (Glx)-deficient diet compared with those fed a control diet. Increase in the voluntary intake of Glx solutions was more rapid in rats fed the Glx-deficient diet. The preference and aversion for MSG solutions were distinctly different in 14 rat strains tested. Brown-Norway rats showed a strong preference for 60 mmol/L MSG and did not show aversive behavior toward solutions containing up to 600 mmol/L MSG. Sprague-Dawley (SD) rats showed a moderate preference for 60 mmol/L MSG and a weak aversion for MSG concentrations higher than 240 mmol/L; Long-Evans Agouti rats showed a moderate preference for 60 mmol/L MSG and a marked aversion for MSG concentrations higher than 120 mmol/L. Aversion was not due to nonspecific hyperosmotic effects. After section of gastric branches of the vagus nerve, MSG became aversive to SD rats. Aversion to 240 mmol/L MSG was reduced by 23-39% when combined with proline, alanine, glycine and glucose. These results show that the preference and aversion for MSG are determined by genetic factors, as well as vagus nerve function, and that the aversion to high MSG concentrations is reduced by the presence of other glucogenic amino acids and sugars.

Low susceptibility of Long-Evans Cinnamon rats to N-butyl-N-(4-hydroxybutyl)-nitrosamine-induced urinary bladder carcinogenesis and inhibitory effect of urinary copper

We studied the susceptibilities to N-butyl-N-(4-hydroxybutyl)nitrosamine (BBN)-induced urinary bladder carcinogenesis of male Long-Evans Cinnamon (LEC), F344 and Long-Evans Agouti (LEA) rats. Male rats (n=21) were given 0.1% BBN in their drinking water from week 6, 8 and 10 for one week, and killed in week 56. The incidences of transitional cell tumors (papillomas plus carcinomas) in BBN-treated LEC and F344 rats were 12% and 76%, respectively (P<0.001, experiment 1), and those in LEC and LEA rats were 11% and 95%, respectively (P<0.001, experiment 2). When male LEC and F344 rats were given 0.1% BBN in their drinking water for 7 days, the intake of BBN and the urinary concentration of its active metabolite, N-butyl-N-(3-carboxypropyl)nitrosamine (BCPN), were higher in the LEC rats (P<0.01). The urinary pHs of untreated LEC and F344 rats were similar between week 6 and 30. The urinary copper concentration was lower in LEC rats before jaundice than in F344 rats, but its concentrations in 28- and 50-week-old LEC rats were 1.7 and 2.3 times those in F344 rats. In a two-stage carcinogenesis study using F344 rats, i.p. injections of cupric nitrilotriacetate increased urinary copper excretion, and inhibited BBN-induced bladder carcinogenesis. In a two-stage carcinogenesis study using LEC rats, oral administration of D-penicillamine decreased urinary copper excretion, and increased BBN-induced bladder cancer, although the difference was not significant. These data show that LEC rats are resistant to bladder carcinogenesis and suggest that urinary copper has a significant role in their resistance.

Analysis of CA repeats in first intron of class I ADH gene in Long-Evans Cinnamon rats developing fatal intoxication after ethanol intake

The Long-Evans Cinnamon (LEC) rat is a mutant strain established from Long-Evans rats that displays spontaneous hepatitis and liver cancer. We previously demonstrated that LEC rats died of acute ethanol intoxication after being fed a liquid diet containing 5% ethanol. Furthermore, we found that both alcohol dehydrogenase (ADH) and aldehyde dehydrogenase activities were remarkably suppressed in the liver of LEC rat, compared with Wistar rats. In the present study, we further investigated ethanol metabolism in the non-ADH pathway and what caused the decrease of liver ADH activity in LEC rats. Blood ethanol concentration 5 hr after intraperitoneal administration of ethanol in LEC rats was higher than in the Wistar rats, indicating that ethanol oxidation was impaired in LEC rats. The expression of liver cytochrome P-450IIE1 in the LEC rat was as much as that in Wistar rats. Regarding decreased ADH activity in the liver of LEC rats, we examined an alternating purine-pyrimidine (CA) repeat-length polymorphism in the first intron of a class I ADH gene that would play a role in altering ADH activity. A polymerase chain reaction method was used to amplify the CA repeat in the first intron of this class I ADH gene, a nine CA repeat insertion and a point mutation were detected in LEC rats. These results suggest that this alternating sequence would modify transcription of the class I ADH gene in LEC rats. Thus, LEC rats have abnormal ethanol metabolism in the ADH pathway.