Adipose tissue thymidine kinase activity in man.

Thymidine kinase activity was studied during human adipose tissue development. Adipose tissue was obtained from the groin in 81 persons, aged 7 wk through 60 yr. None had a metabolic or growth disorder. Adipose tissue thymidine kinase activity was highest in infants and lowest in adults. Peak thymidine kinase activity was seen in the early postnatal period and a lesser elevation was found in the preadolescent years, coinciding with hypothesized periods of proliferation of preadipocytes in man. In contrast, during adulthood, a time of stable lipid-laden cell number, thymidine kinase activity was lower. Although these adipose tissue samples include both stromal and fat cells, the data support the hypothesis that adipose tissue growth in early infancy is primarily the result of cellular proliferation, and that little cellular proliferation occurs after infancy, except possibly for a brief period prior to adolescence.