Growth of adipose tissue in the fetal rabbit

(1) Fetal rabbits of different gestational ages (20-29 days) were obtained by Caesarian section and term rabbits (31 days) by natural delivery. After dissection, organ weights were obtained and growth curves drawn. Brown adipose tissue was first visible at 22 days gestation and increased relatively more quickly than the body weight till day 26 after which it formed a constant percentage of the body weight. Growth of white adipose tissue followed a similar pattern, except that it was not visible until day 24. (2) The percentage triglyceride content of both types of adipose tissue increased throughout the latter part of gestation. (3) Fetuses of low birth weight had depressed fat stores in brown adipose tissue. (4) Some, but not all, of the high birth weight fetuses had relatively enlarged fat stores. (5) It is suggested that the conditions which produce fetuses of unusually low or high birth weight tend to have a greater corresponding effect on the fetal fat stores.