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

✍ Scribed by Thomas, Lynn N.; Cohen, Pinchas; Douglas, Robert C.; Lazier, Catherine; Rittmaster, Roger S.

• Publisher: John Wiley and Sons
• Year: 1998
• Tongue: English
• Weight: 277 KB
• Volume: 35
• Category: Article
• ISSN: 0270-4137
• DOI: 10.1002/(sici)1097-0045(19980601)35:4<273::aid-pros6>3.0.co;2-h

✦ Synopsis

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.