Tohoku J. Exp. Med., 1997, 182 (4)

Genetically Determined Thymus Enlargement in the Early Life in BUF/Mna Rats

MITSUHIRO SAITO, HIROYUKI AMO1, YOSHIKI MURAKUMO, AKINORI KOJIMA2, HIDEKI KATOH3, TAKASHI HIROMATSU and MUTSUSHI MATSUYAMA4

Department of Pathology, Nagoya University School of Medicine, Nagoya 466, 1Aichi Women's College, Nisshin 470-01, 2Nagoya City Public Health Research Institute, Nagoya 467, 3Central Institute for Experimental Animals, Kawasaki 216, and 4Department of Pathology, Fujita Health University School of Medicine, Toyoake 470-11

  • BUF/Mna (B) rat is a mutated strain, having much larger thymus than WKY/ NCrj (W), ACI/NMs (A), and F344 (F) rats throughout their life-span. Rats of the latter 3 strains have normal sized thymuses, being less than 5.3 in the thymus to body weight ratio (mg/g), when they were killed at 6 weeks of age. Genetic segregation of large thymus size in the B strain at 6 weeks of age was studied by crossing B rats with W, A or F rats. All of 3 types of the F1 hybrid rats between the B strain and the other strains showed intermediate thymus ratios between those of both parental strains. In F2 rats between the B and W strains, the distribution of thymus ratios showed about 5 different peaks. These findings might indicate that two polymeric autosomal loci, thymus enlargement-1 (Ten-1) and thymus enlargement-2 (Ten-2), can enlarge the thymus size in B rats. Histometrically, whole thymus and cortcx areas of the B rats were 2-5 times larger than the W rats during 6-12 weeks of age, but medulla areas were slightly different between the strains, showing that larger thymuses in B rats were mainly due to the enlarged cortex areas.
    Key words--- BUF/Mna rats; genetic analysis; Ten-1 and Ten-2; thymus size enlargement; cortex area/medulla area ratio
    © 1997 Tohoku University Medical Press

    Tohoku J. Exp. Med., 1997, 182, 309-318
    Address for reprints: Dr. Mutsushi Matsuyama, Department of Pathology, Fujita Health University School of Medicine, 1-98 Dengakugakubo, Kutsukake-cho, Toyoake-shi, Aichi-ken 470-11, Japan.

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