title: Spontaneous dwarf rat: a novel model for aging research.
abstract: OBJECTIVE
  Dwarf animal models can provide new models for aging research. For the spontaneous dwarf rat (SDR), a dwarf strain derived from the Sprague-Dawley (SD) rat, no data relevant to aging research are available. The present study aimed to examine its growth, hormonal background, lifespan and age-related diseases.
  
  
  METHODS
  Male SDR and SD rats were used for growth comparison and for immunohistochemistry and plasma hormonal analysis. SDR of each sex were maintained until natural death and then inspected pathologically.
  
  
  RESULTS
  SDR showed an apparent dwarfism in their youth. Immunohistochemistry indicated that the development of growth hormone (GH)-positive cells in the pituitary was insufficient in SDR. In SDR, plasma GH levels were lower than in SD rats. Moreover, both insulin-like growth factor-1 (IGF-1) and insulin levels were decreased compared to levels in SD rats. Male and female SDR showed a mean lifespan of 29.3 +/- 3.3 and 26.8 +/- 5.3 months, respectively. The main neoplastic lesions in SDR were pituitary and mammary tumors. Major non-neoplastic lesions were incisor malocclusion, heart disease, chronic nephropathy (male) and cerebral hemorrhage (female). Most cases of chronic nephropathy were mild.
  
  
  CONCLUSIONS
  Compared with longevity data and pathological data reported for SD rats, the lifespan in SDR was increased by 20-40% in males and 10-20% in females, and SDR had characteristic decreases in pituitary and mammary tumors as well as in severe chronic nephropathy. The SDR, differing in endocrinology, longevity and pathology from the SD rat, is potentially a new animal model for aging research.
authors.affiliation: Animal Center, Tokyo Metropolitan Institute of Gerontology, Tokyo, Japan. kuramoto@tmig.or.jp
authors.forename: Kazunao
authors.initials: K
authors.lastname: Kuramoto
authors.forename: Shoichi
authors.initials: S
authors.lastname: Tahara
authors.forename: Toru
authors.initials: T
authors.lastname: Sasaki
authors.forename: Shigenobu
authors.initials: S
authors.lastname: Matsumoto
authors.forename: Takao
authors.initials: T
authors.lastname: Kaneko
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Kondo
authors.forename: Makoto
authors.initials: M
authors.lastname: Yanabe
authors.forename: Shohei
authors.initials: S
authors.lastname: Takagi
authors.forename: Tadashi
authors.initials: T
authors.lastname: Shinkai
mesh_terms: D000375:Aging / Q000473:pathology* / Q000502:physiology*; D000818:Animals; D005260:Female; D013006:Growth Hormone / Q000097:blood; D053208:Kaplan-Meier Estimate; D008297:Male; D023421:Models, Animal; D010902:Pituitary Gland / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D012376:Rodent Diseases / Q000473:pathology / Q000503:physiopathology
chemical_list: D013006:Growth Hormone