Growth of baby kidneys transplanted into adults

To determine whether the growth of a kidney is affected by the age of the host or is independently programmed, baby rat kidneys were isologously transplanted into adult rats that underwent unilateral or bilateral nephrectomies. The growth of these transplanted baby kidneys was compared to the growth of baby kidneys that were left intact in the growing baby rat. After allowing for compensatory hypertrophy, the kidneys, whether in babies or adults, were found to grow at the same rate and to the same ultimate size. Renal size could be predictably related to renal age, but not to the age of the host.