Abstract: Objective To breed the inbred strain of dwarf rat and determine the main biological characteristics. Methods The spontaneous mutant litters looks like dwarfism from the Wistar conlony was bred and maintained by brother×sister (B×S) mating system for 22-23 progenies and nominatured as spontaneous dwarfism rat (SDWR) according the standard. As reference of strain, indexes of growth and development, body measurements, reproductive performance, organ weight, serum biochemical (12 items) and hematology (12 items) about dwarf rat at different age stages were measured, and be compared with background Wistar rat. Results Up to February 2016, the dwarf rat was inbreded continuously for 22-23 generations, and named as SDWR temporarily. The weight of weanling, youth and adult individuals in SDWR was respectively only about 45.7%, 37.5%, 36.2%(♂) and 49.7%, 41.7%, 40.3%(♀) of the same age Wistar rats (P<0.01). The body and tail length of youth and adult individuals in SDWR is respectively 77.5%, 72.3% (♂) and 73.8%, 68.9%(♀) of Wistar rats (P<0.01). The weights of major organs (heart, liver, spleen, lung, kidney, testis or oviduct tubes) in youth and adult SDWR are significantly lower than that of the same ages Wistar rats (P<0.01). Conclusions Through 22-23 progenies inbreeding, the established inbreeding strain of SDWR exhibited obvious dwarfism symptoms in growth, body measurements, reproductive performance and organs weight, and has stable heredity. The rat may be useful as animal models for the study of inherited dwarfism in human.

Key words: Dwarfism, Inbred strain, Spontaneous dwarfism rat (SDWR), Body mass, Body size, Organ weight, Physiological and biochemical indexes of blood