Sex differences in the renal transforming growth factor-β1 system after puberty

Transforming growth factor-beta1 (TGF-beta1) has been implicated in many progressive kidney diseases. The present study examines this growth factor during the pubertal and early adult periods. Mixed-sex Munich-Wistar rat kidneys were obtained on selected days of life from birth through 6 months of age. A survey of the TGF-beta1 system was performed, and then a second experiment focused on cortex and medulla from both sexes at 6 weeks and 16 weeks of age. Reverse transcription polymerase chain reaction for TGF-beta1 and TGF-beta inducible gene H3 (beta IG-HS) was performed. Active and total levels of protein for TGF-beta1 were isolated from tissue. Active levels of TGF-beta1 were somewhat lower in older than in younger animals, without sex differences. beta IG-H3 levels were similar. At 16 weeks females had levels of total growth factor approximately threefold greater than males, while adult males appeared to activate the growth factor much more efficiently. These findings suggest that activation of TGF-beta1 becomes more efficient following puberty in the male rat, while females appear to have reduced activation efficiency compensated by increased total growth factor. These differences may help explain the deterioration at puberty and sexual dimorphism noted with some progressive nephropathies.