title: Experimental models of hepatectomy and liver regeneration using newborn and weaning rats.
abstract: OBJECTIVE
  Liver regeneration is a complex process that has not been completely elucidated. The model most frequently used to study this phenomenon is 70% hepatectomy in adult rats; however, no papers have examined this effect in developing animals. The aims of the present study were: 1) to standardize two models of partial hepatectomy and liver regeneration in newborn suckling and weaning rats, and 2) to study the evolution of remnant liver weight and histological changes of hepatic parenchyma on the days that follow partial hepatectomy.
  
  
  METHODS
  Fifty newborn and forty-four weaning rats underwent 70% hepatectomy. After a midline incision, compression on both sides of the upper abdomen was performed to exteriorize the right medial, left medial and left lateral hepatic lobes, which were tied inferiorly and resected en bloc. The animals were sacrificed on days 0 (just after hepatectomy), 1, 2, 3, 4 and 7 after the operation. Body and liver weight were determined, and hepatic parenchyma was submitted to histological analysis.
  
  
  RESULTS
  Mortality rates of the newborn and weaning groups were 30% and 0%, respectively. There was a significant decrease in liver mass soon after partial hepatectomy, which completely recovered on the seventh day in both groups. Newborn rat regenerating liver showed marked steatosis on the second day. In the weaning rat liver, mitotic figures were observed earlier, and their amount was greater than in the newborn.
  
  
  CONCLUSIONS
  Suckling and weaning rat models of partial hepatectomy are feasible and can be used for studies of liver regeneration. Although similar, the process of hepatic regeneration in developing animals is different from adults.
authors.affiliation: Pediatric Surgery Laboratory, Function Research Laboratory, Faculdade de Medicina, Universidade de São Paulo, São Paulo, SP, Brazil. cristannuri@uol.com.br
authors.forename: Ana Cristina Aoun
authors.initials: AC
authors.lastname: Tannuri
authors.forename: Uenis
authors.initials: U
authors.lastname: Tannuri
authors.forename: Maria Cecília
authors.initials: MC
authors.lastname: Coelho
authors.forename: Neide Aparecida Dos
authors.initials: NA
authors.lastname: Santos
authors.forename: Evandro Sobroza de
authors.initials: ES
authors.lastname: Mello
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D000833:Animals, Suckling; D006498:Hepatectomy / Q000379:methods*; D007165:Immunosuppression Therapy; D008115:Liver Regeneration / Q000502:physiology*; D023421:Models, Animal; D009929:Organ Size; D051381:Rats; D014886:Weaning