1. Sponsor Organization: MEDICAL RESEARCH COUNCIL OF CANADA

2. Project Title: REGULATION OF EPIDIDYMAL FUNCTION

3. Project Focus:

• Project Primary Focus: Exposure Assessment
• Project Secondary Focus: Human Health Effects

4. Description:

The lack of an in depth understanding of androgen action and of the functions and regulation of the epididymis and other androgen dependent tissues have prevented more rapid strides in understanding endocrine disruptors or in developing effective therapeutic approaches. Our focus is on how the enzymes that synthesize the endogenously most active androgen, dihydrotestosterone (DHT), are controlled in the epididymis at the DNA, RNA, protein and enzyme levels, and second, on the cellular and molecular changes that occur in the epididymis when androgen/other input to this tissue are changed. We are investigating the regulation of epididymal 5`-Rs at several levels. At the genomic level, we are identifying the minimal promoter for the two genes in order to establish the location and sequence of the bases that are key in controlling gene expression. This should permit the identification of factors that modulate the expression of the 5`-R genes. We will then establish which transcription factors are present and functional throughout the epididymis in the regulation of the two 5`-R genes. Remarkable changes take place in the steady state concentrations of both types 1 and 2 5`-R mRNAs under different conditions. To ascertain the relative importance of synthesis and breakdown of mRNAs, we are determining rates of mRNA transcription and turnover. The intracellular distribution of the type 1 5`-R protein within epididymal principal cells changes as one progresses down the epididymal duct. We have obtained antibodies to the type 2 protein and will assess how the exact intracellular distribution of the enzymes differ, and how their intracellular and longitudinal distributions are affected by factors such as testicular input or androgens. We hypothesize that the distribution of the type 2 enzyme may change in a very different way than would type 1 after efferent duct ligation or orchidectomy. The consequences of inhibiting epididymal 5`-R is being investigated by taking advantage of newly discovered inhibitors that are selective for each of the two enzymes. It is now possible to establish, using this approach, the exact role of the two 5`-Rs in epididymal function, in particular and more generally, in androgen action. We have been investigating the relative roles of androgens and direct testicular secretions in regulating specific proteins, e.g. 5`-R, cadherins, clusterin. However, relatively little is known about the net cellular effects of altering epididymal exposure to androgens and testicular secretions. We have established a role for apoptosis after androgen withdrawal. We propose to resolve the relative role of apoptosis; several markers associated with this process, will be examined. Clusterin seems to play multiple roles in the epididymis including taking part in apoptosis and sperm maturation; yet, its complex regulation remains largely a mystery. The remarkable difference in the distribution of the subunits of the GSH-transferases in different regions of the epididymis has led us to speculate that these enzymes protect the tissue from electrophilic attack. We are investigating how these enzyme are regulated and how they respond to an increased "electrophilic load". Understanding androgen action and using the epididymis as a model tissue should provide better insight into how endocrine disruptors can mediate several conditions that afflict man today.

5. References:

6. Inventory Category:

• Primary: Models
• Secondary:

7. Inventory Subcategory:

• Primary: Biomakers
• Secondary:
  • Basic Research

8. Keywords for Experimental System/Species:

• Species:
  • Mammal
  • Rodents
• Study Type:
  • In Vitro
  • In Vivo
  • Laboratory Study
• Fate and Transport:

9. Keywords for Experimental Endpoints:

• Health Effect:
  • Reproductive
• Hormonal Measures:
  • Sex Steroids
• Level Of Study:
  • Histopathology
  • Physiology
  • Biochemistry
  • Gene Expression
• Chemistry Metabolism:
• Life Stage:
  • Male
  • Adult
• Risk Assessment:

10. Chemical Agents:

• Androgens/Anti-Androgens
• Mercury
• Methylmercury

11. Performing Institution:

• Department of Pharmacology and Therapeutics, McGill University, 3655 Drummond Street, Montreal, Quebec, H3G 1Y6

12. Contact:

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