Antihormone activity

The chemical structures of the parent hormones and some examples of antagonists for each of the major classes of steroid hormones are illustrated in Fig. 3. It is important to recognize that each of these compounds blocks hormone action at the receptor level. In in vivo tests for hormonal or antihormonal activity the ap-... 

Of special interest is the fact that certain plants synthesize secondary products which in animals possess hormone or antihormone activity. Either the true animal hormones are formed (Table 59) or substances are built which mimic the animal hormones (Table 76). Both types of compounds may cause metabolic and developmental abnormalities in the predators, reduce reproduction, or, in the case of the trichomes of the stinging nettel (Urtica dioica) containing histamine (D 20) and serotonin (D 21.1), cause irritation of in the skin after injection which may repel predators. Rather large quantities of the hormones may be produced, as is shown by the fact that from 1 g of dried rhizomes of the fern Polypodiurn vulgare, 10 mg ecdysterone were isolated, in striking contrast to the 0.33 mg isolated from a ton of silkworms. 

Table 76. Secondary plant products which mimic the action of animal hormones or show antihormone activity...

Several studies have shown the ability of DNMT inhibitors to prevent cancer using different pathways [101-104]. Genistein demonstrated cancer chemopreventive activities in animal models [105]. It has been studied in different cancer cell lines and inhibition of cancer cell growth has been shown [106]. But several mechanisms, such as antihormonal effects, are discussed to explain this activity and the exact contribution of DNMT inhibition to in-vivo activity in cancer chemoprevention remains to be determined. 

Another group of compounds are the thyrostats, which are sometimes called antihormones because they inhibit the activity of the thyroid gland. 

Allan GF, Leng X, Tsai SY, Weigel NL, Edwards DP, Tsai M-J, O Malley BW. Hormone and antihormone induce distinct conformational changes which are central to steroid receptor activation. J. Biol. Chem. 1992 267 19513-19520. 

Schuetz, E.G., C. Brimer and J.D. Schuetz. Environmental xenobiotics and the antihormones cyproterone acetate and spironolactone use the nuclear hormone pregnenolone X receptor to activate the CYP3A23 hormone response element. Mol. Pharmacol. 54 1113-1117, 1998. 

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