Related Experiment Video
Updated: Aug 13, 2026
Murine Prostate Micro-dissection and Surgical Castration
Published on: May 11, 2016
Differential effect of 5 alpha-reductase inhibition and castration on androgen-regulated gene expression in rat
R S Rittmaster1, K E Magor, A P Manning
1Department of Medicine and Physiology, Dalhousie University, Halifax, Nova Scotia, Canada.
Abstract:
Castration reduces prostate size and causes intraprostatic testosterone (T) and dihydrotestosterone (DHT) to fall to very low levels. 5 alpha-Reductase inhibition also reduces prostate size, but results in a marked increase in intraprostatic T levels. To compare the effects of 5 alpha-reductase inhibition and castration on prostate physiology, male Sprague-Dawley rats were left intact, castrated, or given the selective 5 alpha-reductase inhibitor finasteride for up to 9 days. To be sure that finasteride itself did not directly affect gene expression, an additional group of rats was castrated and given finasteride for 4 days. The prostates were weighed, intraprostatic RNA, DNA, and androgen levels were measured, and mRNAs for two androgen-regulated genes, prostate steroid-binding protein (PSBP; an androgen-induced gene) and testosterone-repressed prostate message (TRPM-2), were quantitated by Northern and slot blot analyses. Finasteride caused a 95% reduction in intraprostatic DHT levels and a 10-fold increase in intraprostatic T levels. Finasteride, as expected, caused a pronounced decrease in prostate weight (45% on day 4). DNA content fell correspondingly (48% on day 4). Intraprostatic DNA (micrograms of DNA per gland) on day 4 was 328 +/- 53 in control rats, 171 +/- 10 in finasteride-treated rats (P less than 0.001 compared to controls), 115 +/- 2 in castrated rats (P less than 0.05 compared to finasteride), and 107 +/- 43 in finasteride-treated plus castrated rats (P = NS compared to castration alone). There were no significant differences in DNA levels among the groups when expressed per mg prostate tissue, indicating that mean prostate cell size was unchanged.(ABSTRACT TRUNCATED AT 250 WORDS)
Insights
Comparing castration and 5 alpha-reductase inhibition reveals distinct effects on prostate physiology. Finasteride significantly reduces dihydrotestosterone (DHT) while increasing testosterone (T), impacting prostate weight and DNA content differently than castration.
Area of Science:
- Endocrinology and Urology
- Molecular Biology
Background:
- Castration drastically lowers intraprostatic testosterone (T) and dihydrotestosterone (DHT), reducing prostate size.
- 5 alpha-reductase inhibition also reduces prostate size but paradoxically elevates intraprostatic T levels.
Purpose of the Study:
- To compare the distinct physiological effects of 5 alpha-reductase inhibition versus castration on the prostate.
- To investigate the impact of finasteride on intraprostatic androgen levels and gene expression in rat prostates.
Main Methods:
- Male Sprague-Dawley rats were subjected to intact, castration, or finasteride treatment for up to 9 days.
- Prostate weight, intraprostatic RNA, DNA, and androgen levels were measured.
- Quantitative Northern and slot blot analyses were used to measure mRNAs for androgen-regulated genes (PSBP, TRPM-2).
Main Results:
- Finasteride treatment led to a 95% reduction in intraprostatic DHT and a 10-fold increase in T.
- Finasteride significantly decreased prostate weight (45%) and DNA content (48%) by day 4.
- Castration resulted in lower prostate DNA content per gland compared to finasteride treatment, with no significant difference when combined.
Conclusions:
- 5 alpha-reductase inhibition and castration exert differential effects on prostate physiology and androgen metabolism.
- Finasteride's impact on prostate involution differs from castration, highlighting the distinct roles of DHT and T in prostate maintenance.
