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Insulin‐like growth factor binding protein 5 is associated with involution of the ventral prostate in castrated and finasteride‐treated rats
Author(s) -
Thomas Lynn N.,
Cohen Pinchas,
Douglas Robert C.,
Lazier Catherine,
Rittmaster Roger S.
Publication year - 1998
Publication title -
the prostate
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.295
H-Index - 123
eISSN - 1097-0045
pISSN - 0270-4137
DOI - 10.1002/(sici)1097-0045(19980601)35:4<273::aid-pros6>3.0.co;2-h
Subject(s) - finasteride , involution (esoterism) , prostate , endocrinology , apoptosis , medicine , dna fragmentation , dihydrotestosterone , tunel assay , staining , programmed cell death , biology , androgen , immunohistochemistry , hormone , cancer , consciousness , biochemistry , genetics , neuroscience
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 5α‐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. Prostate 35:273–278, 1998. © 1998 Wiley‐Liss, Inc.