The influence of hypothyroidism on liver regeneration: an experimental study in rats.
BACKGROUND
The influence of hypothyroidism in liver regeneration has been a controversial opinions.


OBJECTIVE
The aim of this study is to identify the relationship between hypothyroidism and liver regeneration in rats.


METHODS
Forty male Wistar rats divided into two groups of 20 specimens each. One group (C) consisted of euthyroid rats, and the other (H) of hypothyroid rats. All the animals were anesthetized with xylazine and ketamine and subjected to a longitudinal incision in the anterior cervical region. The thyroid was completely resected in group H and left intact in group C. Ten days after the first surgery, both groups of rats were weighed and submitted to partial hepatectomy, in which the left lateral and median lobes were resected and weighed. Examinations were carried out after 24 hours and, on day 7, using 3 methods: KWON et al.'s formula to identify increase in volume; mitotic figure count in five fields; and the percentage of PCNA-positive nuclei in five fields.


RESULTS
Using KWON's formula, the regeneration rate for Group C after 24 hours was 58.49% whereas that for Group H was 50.42% (p=0.0165). After 7 days, the regeneration rate for Group C was 93.04% and Group H 93.74% (p=0.2165). The average number of mitotic figures after 24 hours was 14 +/- 1.5 for Group C and 9.8 +/- 2.2 for Group H (p=0,00016). After 7 days the corresponding figures were 5.4 +/-1.1 and 5.1+/- 1.2 (p=0,6343). The average number of PCNA-positive nuclei after 24 hours was 13.55+/- 3.84 in Group C and 7.7 +/- 2.11 in Group H (p =0,0006)). The corresponding figures after 7 days were 3.5 +/- 2.39 for Group C and 4.11 +/-1.90 for Group H (p>0.05).


CONCLUSIONS
We conclude that hypothyroidism in rats causes a delay in hepatic regeneration in the first 24 hours, but that after seven days the rate of regeneration is equal to that in euthyroid rats.
Biondo-Simões
Maria de Lourdes Pessole
Mde L
Department of Surgery, School of Medicine, Universidade Federal do Paraná, CEP 82030-000 Curitiba-Paraná, Brazil. biondo@avalon.sul.com.br
Castro
Gustavo Rodrigues Alves
GR
Montibeller
Guilherme Ramina
GR
Sadowski
José Augusto
JA
Biondo-Simões
Rachel
R
D000818:Animals; D004195:Disease Models, Animal; D006498:Hepatectomy; D007037:Hypothyroidism / Q000503:physiopathology*; D008099:Liver / Q000502:physiology*; D008115:Liver Regeneration / Q000502:physiology*; D008297:Male; D018809:Proliferating Cell Nuclear Antigen / Q000032:analysis; D051381:Rats; D017208:Rats, Wistar; D013965:Thyroidectomy
D018809:Proliferating Cell Nuclear Antigen