正常と糖尿病自然発症Wistar系シロネズミの子孫に関する実験的研究

抄録

Two male Wistar-strain rats in the F₇ generation (Experiment A), which were obtained by successive mating of alloxan-diabetic males and non-diabetic females for 7 generations, and two rats in the F₅ generation (Experiment B), which were obtained by successive mating of alloxan-diabetic males and alloxan-diabetic females for 5 generations, were mated with normal Wister-strain rats in order to obtain the offsprings which are called F₁ rats in the present experiment. All of the male parents had “spontaneous diabetes”; and the former, in Experiment A, brother-sister breeding was continued until the F₅ rats were obtained. In Experiment B, mating the F₁ males and normal females was carried out until the F₃ animals were obtained. A total of ninety rats thus obtained in both Experiment A and B were sacrificed on the 90th day after birth, weighing over 150 grams examined histometrically.
The following results were obtained, comparing with 7 normal rats of the same age and body weight.
1) No marked difference in the increase of body weight was found between the experimental rats and normal rats.
2) None of the experimental animals showed the signs of development of “spontaneous diabetes”.
3) No significant changes were found in the glandular cells of the pancreas. A slight decrease in the number and area of α-cells of Langerhans' islets was able to be found in the F₁ animals of both Experiment A and B. No other significant changes in α-cells could be found in the later generations of mating.
4) The following remarkable changes were found, however, in the β-cells of Langerhans' islets :
(a) The F₁ rats in both Experiment A and B, obtained by the mating normal females (number of β-cells being 66.7 in average) and “spantaneous diabetic” males (number of β-cells being 17 in average), had 35.3 to 45.6 β-cells, an average of 39.8±2.7, this value being slightly less than the mean of β-cells of the parents.
(b) In Experiment A, the youngs obtained from the mating within the littermates in the F₁ had 47.7 to 53.7 β-cells, an average of 50.8±1.6 ; the youngs within the littermates in the F₂ 55.2 to 60.3, an average of 57.8±1.8 ; the youngs within the littermates in the F₃ 63.6 to 65.4, an average of 65.0±0.8 ; the youngs within the littermates in the F₄ 63.8 to 69.3, an average of 66.9±1.7. The value in the F₄ was almost identical with that of normal rats, the recovery to normal condition being seen, therefore, in the F₄ offsprings.
(c) The youngs (F₂ rat) obtained from the mating normal females (number of β-cells being 66.7) and the F₁ males in Experiment B (number of β-cells being 38.3) had 54.4 to 57.8 β-cells, an average of 56.4±1.0 ; the youngs from the mating normal females (66.7) and the F₂ (56.4) had 62.1 to 68.1, an average of 64.3±2.2. These findings indicate that the number of the β-cell increases much more rapidly approaching the normal value in Experiment B than in Experiment A, being illustrated in (b), in which mating is made within the littermates from non-diabetic parents with diabetic disposition.
5) The following results were obtained in the area of both β-cell and Langerhans' islet of the pancreas :
(a) A slight decrease from normal value was seen in the F₁ rats in both Experiment A and B.
(b) In the youngs (F₂ to F₅ in Experiment A) from mating within the littermates, obtained from the non-diabetic parents with diabetic disposition, a slight increase over their respective parents was seen, with a tendency to approach the normal value as the mating generation advanced.