Thought you guys would enjoy the read
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Androgen Receptor Regulation
Publication Date: August 1998 by bill roberts
Nothing in this article is intended to take the place of advice from a licensed health professional. Consult a physician before taking any medication.
One of the most common beliefs concerning anabolic/androgenic steroid (AAS) usage is that the androgen receptor (AR) downregulates as a result of such usage. This has been claimed repeatedly in many books and articles, and it is claimed constantly on bulletin boards and the like. If I’ve heard it once, I’ve heard it a thousand times. If it were just being stated as an abstruse hypothesis, with no practical implications, with no decisions being based on it, that might be of little importance.
Unfortunately, this claim is used to support all kinds of arguments and bad advice concerning practical steroid usage. Thus, the error is no small one.
We will look at this matter fairly closely in this article. However, in brief the conclusions may be summed up as follows:
• There is no scientific evidence whatsoever that AR downregulation occurs in human muscle, or in any tissue, in response to above normal (supraphysiological) levels of AAS.
• Where AR downregulation in response to AAS has been seen in cell culture, these results do not apply because the downregulation is either not relative to normal androgen levels but to zero androgen, or estrogen may have been the causative factor, or assay methods inaccurate for this purpose were used, or often a combination of these problems make the results inapplicable to the issue of supraphysiological use of androgens by athletes.
• AR upregulation in response to supraphysiological levels of androgen in cell culture has repeatedly been observed in experiments using accurate assay methods and devoid of the above problems.
• AR downregulation in response to AAS does not agree with real world results obtained by bodybuilders, whereas upregulation does agree with real world results. (A neutral position, where levels in human muscle might be thought not to change in response to high levels of androgen, is not disproven however.)
• The "theoretical" arguments advanced by proponents of AR downregulation are invariably without merit.
The belief that androgen receptors downregulate in response to androgen is one of the most unfounded and absurd concepts in bodybuilding.
While this may seem perhaps an overly strong condemnation of that view, please consider that the claims for downregulation seen in books such as Anabolic Reference Guide (6th Issue), World Anabolic Review, Underground Steroid Handbook, etc. are presented with absolutely no evidence whatsoever to support them. The authors merely assert downregulation. They have done it so many times that by now many people assume it is gospel. In this paper you will be provided with evidence, and the evidence does not support their claim.
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Overview of Regulation
Meaning of regulation
"Regulation" of a receptor refers to control over the number of receptors per cell. "Sensitivity," in contrast, refers to the degree of activity each receptor has. It is a possible in many cases for the receptors of a cell to be sensitized or desensitized to a drug or hormone, independently of the number of receptors. Similarly, it is possible for the receptors to upregulate or downregulate, to increase or decrease in number, independently of any changes in sensitivity.
If sensitivity remains the same, then upregulation will yield higher response to the same amount of drug or hormone, and downregulation will result in less response.
So if we are discussing androgen receptor regulation, we are discussing how many ARs are present per cell, and how this may change.
Changes in regulation must, of necessity, be between two different states, for example, levels of hormone. In the case of bodybuilding, we are interested in supraphysiological levels vs. normal levels (or perhaps, a higher supraphysiological level vs. a lower supraphysiological level.) In most research that is done, the comparison is often between normal levels and zero levels, or the castrated state.
We may describe regulation with the two levels being in either order. Upregulation as levels decrease from normal to zero is the same thing, but in the reverse direction, as downregulation as levels increase from zero to normal.
The term which would be used will depend on context, but does not change meaning, so long as the direction of change in level of hormone is understood.
If upregulation occurs as levels decrease from normal to zero, as is probably the case in some tissues, this would imply nothing about what may happen as levels increase beyond normal. It does not prove that downregulation would occur. It would be a serious error to take a study comparing normal levels and zero levels and use that study to argue the effect of supraphysiological levels. Unfortunately, such mistakes are commonly made by authors in bodybuilding.
Forms of regulation
Broadly speaking, there are three things that control the number of receptors. To understand them, let’s quickly review the life-cycle of an individual AR.
There is a single gene in the DNA of each cell that codes for the AR. In the transcription process, the DNA code is copied to mRNA. The rate (frequency) of this process can be either increased (promoted) or decreased (repressed) depending on what other proteins are bound to the DNA at the time. Increase or decrease of this rate can be a form of regulation: the more AR mRNA is produced, all else being equal, the more ARs there will be. However, all else rarely is equal.
If efficiency is 100%, each mRNA will be used by a ribosome to produce an AR, which is a protein molecule. The process of making protein from the mRNA code is called translation. In practice efficiency will not be 100%. Changes in efficiency of translation can also be a form of regulation.
The third contributing factor to regulation is the rate of loss of ARs. If the cell produces x ARs per hour, and their half life is say 7.5 hours, then the number of ARs will be higher than if ARs are produced at that same rate but the half life is say only 3.3 hours. Thus, control of rate of turnover, or change in half-life, can be another means of regulation.