Insulin-like growth factor binding protein 5 is associated with involution of the ventral prostate in castrated and finasteride-treated rats

Prostate. 1998 Jun 1;35(4):273-8. doi: 10.1002/(sici)1097-0045(19980601)35:4<273::aid-pros6>;2-h.


Background: Insulin-like growth factor binding protein (IGFBP)-5 has been proposed as a signal for apoptosis in the ovary. To determine the relationship between IGFBP-5 and apoptosis during regression of the androgen-deprived prostate, rats were castrated or treated with the 5alpha-reductase inhibitor finasteride for 4, 9, 14, 21, and 28 days.

Methods: Ventral prostate tissue was immunostained for IGFBP-5, and apoptotic cells were identified by in situ end-labeling of fragmented DNA (TUNEL). To compare the distribution of IGFBP-5 with the distribution of apoptotic cells, mirror-image serial sections of prostate tissues from normal and day 4 finasteride-treated rats were examined.

Results: In normal rats, 4+/-1% of prostate epithelial cells stained positively for IGFBP-5, and 0.1+/-0.03% demonstrated DNA fragmentation. IGFBP-5 staining peaked at day 9 with 93 +/-2% and 64+/-13% of epithelial cells staining positively in castrated and finasteride-treated rats, respectively. In contrast, DNA fragmentation peaked at day 4 in tissues from both castrated and finasteride-treated rats with 7+/-1% and 0.7+/-0.3% of epithelial cells, respectively, staining. In the serial sections, TUNEL and IGFBP-5 staining were not usually expressed in the same cells.

Conclusions: Prostatic involution involves both programmed cell death and inhibition of cell growth. Because of the distribution of staining and the delayed expression of IGFBP-5 relative to initiation of apoptosis, we postulate that IGFBP-5 functions as an inhibitor of cell proliferation rather than as a signal for apoptosis.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Apoptosis*
  • DNA Fragmentation
  • Epithelial Cells / cytology
  • Epithelial Cells / drug effects
  • Epithelial Cells / physiology
  • Finasteride / pharmacology*
  • Insulin-Like Growth Factor Binding Protein 5 / analysis
  • Insulin-Like Growth Factor Binding Protein 5 / metabolism*
  • Male
  • Orchiectomy*
  • Prostate / cytology
  • Prostate / drug effects
  • Prostate / physiology*
  • Rats
  • Rats, Sprague-Dawley
  • Reference Values


  • Insulin-Like Growth Factor Binding Protein 5
  • Finasteride