Акселерация лабораторных крыс: синтетическое Исследование данных за столетие в аспекте возможной связи с радиочувствительностью

Abstract

Purpose: A synthetic study of published data on the growth and development of laboratory rats (albino random-bred, Wistar and Long–Evans) depending on the period of their breeding since 1906 was carried out. Material and methods: Data for the dynamics of growth and age periods of rats were used for calculations and general analysis. Results: Acceleration in terms of age–weight indices for strain animals was found: in conditions of complete diets ad libitum the contemporary rats grew several times faster than the bred ones of 1906–1932. For random-bred rats only the tendency to acceleration was obtained. For more than a century, the Wistar males showed an inverse linear correlation between the breeding year and the age (in weeks) at the of the onset of puberty period (according to the Spearman test: r = –0.952; p = 0.00026; Pearson’s criterion: r = –0.950, p = 0.0003). There was also a direct correlation between the body mass of rats at the time of puberty onset and the year of their breeding (according to the Spearman test: r = 0.975; p = 0.005; Pearson criterion: r = 0.927; p = 0.023). The possible reasons for the acceleration of laboratory growth of rats, which are unlikely to be analogous to the factors presumably causing the known ‘growth acceleration’ in humans (changes in natural and artificial lighting, the effect of heterosis, improvement of socio-hygienic conditions, the growth of information flow, warming of the climate, change in the geomagnetic or radiation background, etc.) were discussed. Apparently, in addition to the probability of special and/or subconscious selection during century, the stimulation of rat acceleration may be explained by the ‘increase in living space and resources’ due to improved standards for keeping animals in the modern period (fewer animals in the cage or even an individual cage). In random-bred animals such standards can be apply for economic reasons to a lesser extent. Conclusions: It is concluded that the physiological, anatomical, possibly behavioral and other standards and patterns for strain rats, including, possibly, its radiosensitivity, published even 30 years ago, and especially more than 50 years ago, should be cautiously transferred to the animals grown under present-day conditions.