Androgenic activity surface

Blankvoort, B.M.G., Richard, J.T., Rodenburg, Murk, A.J., Koeman, J.H., Schilt, R., Aarts, M.M.J.G. (2005). Androgenic activity in surface water samples detected using the AR-LUX assay indications for mixture effects. Environmental Toxicology and Pharmacology 19, 263-272. 

Figure 25-5. Metabolism of high-density lipoprotein (HDL) in reverse cholesteroi transport. (LCAT, lecithinxholesterol acyltransferase C, cholesterol CE, cholesteryl ester PL, phospholipid A-l, apolipoprotein A-l SR-Bl, scavenger receptor B1 ABC-1, ATP binding cassette transporter 1.) Prep-HDL, HDLj, HDL3—see Table 25-1. Surplus surface constituents from the action of lipoprotein lipase on chylomicrons and VLDL are another source of preP-HDL. Hepatic lipase activity is increased by androgens and decreased by estrogens, which may account for higher concentrations of plasma HDLj in women.

LH promotes synthesis of testosterone, the major male androgen (Box 11.5) by the testicular Leydig cells. FSH sensitizes these cells to the activities of LH, probably by increasing LH receptor numbers on the cell surface. Leydig cells have a limited storage capacity for testosterone ( 25 pg), but secrete 5-10 mg of the hormone into the bloodstream daily in young healthy males. 

The mechanisms of action of steroid hormones on lymphoid, mammary, and prostatic cancer have been partially clarified. Specific cell surface receptors have been identified for estrogen, progesterone, corticosteroids, and androgens in neoplastic cells in these tissues. As in normal cells, steroid hormones also form an intracellular steroid-receptor complex that ultimately binds directly to nuclear proteins associated with DNA to activate transcription of a broad range of cellular genes involved in cell growth and proliferation (see Chapter 39 Adrenocorticosteroids Adrenocortical Antagonists). 

In man and in other mammalian species, the major mass of the prostate, usually consisting of the right and left lateral and the middle lobes, is composed of alveoli lined with columnar epithelium embedded in a thick fibromuscular stroma. These alveoli constantly secrete a fluid which is drained off by a system of branching ducts that empty into the floor and lateral surfaces of the posterior urethra. The normal secretion is dependent upon the degree of androgenic stimulation and amounts to about 0.5-2 ml per day. The prostatic secretion, which is characterized by very high acid phosphatase activity, is a milky fluid which contains citric acid, choline, cephalin, cholesterol, proteins, and electrolytes similar to those found in the plasma. 

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