Other Steroids

Cholesterol is the central compound m any discussion of steroids Its name is a combination of the Greek words for bile (chole) and solid (stereos) preceding the characteristic alcohol suffix ol It is the most abundant steroid present m humans and the most important one as well because all other steroids arise from it An average adult has over 200 g of cholesterol it is found m almost all body tissues with relatively large amounts present m the brain and spinal cord and m gallstones Cholesterol is the chief constituent of the plaque that builds up on the walls of arteries m atherosclerosis... 

Cholesterol is biosynthesized in the liver trans ported throughout the body to be used in a va riety of ways and returned to the liver where it serves as the biosynthetic precursor to other steroids But cholesterol is a lipid and isn t soluble in water How can it move through the blood if it doesn t dis solve in if The answer is that it doesn t dissolve but IS instead carried through the blood and tissues as part of a lipoprotein (lipid + protein = lipoprotein) The proteins that carry cholesterol from the liver are called low density lipoproteins or LDLs those that return it to the liver are the high-density lipoproteins or HDLs If too much cholesterol is being transported by LDL or too little by HDL the extra cholesterol builds up on the walls of the arteries caus mg atherosclerosis A thorough physical examination nowadays measures not only total cholesterol con centration but also the distribution between LDL and HDL cholesterol An elevated level of LDL cholesterol IS a risk factor for heart disease LDL cholesterol is bad cholesterol HDLs on the other hand remove excess cholesterol and are protective HDL cholesterol IS good cholesterol... 

Steroid Antibiotics. The steroid antibiotics are a stmcturaHy diverse class of steroids that have a common biological function, ie, antibacterial, antifungal, antiviral, or antitumor activities. This group of compounds can overlap with other steroid classes Hsted above. Eusidic acid [6990-06-3] (67), helvohc acid [29400-42-8] (68), and cephalosporin [13258-72-5] (69) exemplify a set of antibacterial steroids that contain a prolanostane skeleton with an... 

A third advancement in microbial biotechnology of steroid production was the abiUty to introduce a 16a-hydroxyl group microbiologicaHy (163). Modifications of the liP-hydroxylation, 16a-hydroxylation 1,2-dehydrogenation microbial processes are used for the synthesis of hydrocortisone, prednisolone, triamcinolone, and other steroid pharmaceuticals. A few microbial transformations that have been used to manufacture steroids are Hsted in Table 1 (164). 

Estranes. Investigations into the total synthesis of steroids began in the 1930s shordy after the precise formula for cholesterol was estabUshed. The eadiest studies focused on equilenin (5) because of its relative stereochemical simplicity when compared to other steroid nuclei Initially, equilenin was synthesi2ed in 20 chemical steps with an overall yield of 2.7%. This synthesis helped to confirm the perhydro-l,2-cyclopentenophenanthrene ring system of... 

In addition to the sex hormones and corticosteroids, other steroid dmgs have substantial worldwide markets. For example, cytostatic hormones had worldwide sales of approximately 1.8 biUion in 1994. Included in these 1.8 biUion are several steroids or steroid-mimetics such as megestrol acetate and tamoxifen (282), respectively (262). 

Cholesterol is biosynthesized in the liver, transported throughout the body to be used in a variety of ways, and returned to the liver where it serves as the biosynthetic precursor to other steroids. But cholesterol is a lipid and isn t soluble in water. How can it move through the blood if it doesn t dissolve in it The answer is that it doesn t dissolve, but is instead carried through the blood and tissues as part of a lipoprotein (lipid + protein = lipoprotein). 

The most prevalent steroid in animal cells is cholesterol (Figure 25.30). Plants contain no cholesterol, but they do contain other steroids very similar to cholesterol in structure (see page 256). Cholesterol serves as a crucial component of cell membranes and as a precursor to bile acids (e.g., cholate, glycocholate,... 

Pregnenolone and Progesterone Are the Precursors of All Other Steroid Hormones... 

The great variety of structures that have by now been shown to exhibit estrogenic activity leads to the suspicion that the estrogen receptor may be unusually nonspecific compared to receptors for other steroid hormones. 

Again, as in the case of the other steroid hormones, the quantities of these compounds isolable from animal sources was... 

Examination of the dates on the references to this chapter will quickly reveal that publications on the corticoids, as indeed all other steroids, reached a steep maximum in the late 1950s to about 1960. After that, publication dropped off to a comparative trickle. It should be kept in mind when examining... 

Lipids are classified into two broad types those like fats and waxes, which contain ester linkages and can be hydrolyzed, and those like cholesterol and other steroids, which don t have ester linkages and can t be hydrolyzed. 

From lanosterol, the pathway for steroid biosynthesis continues on to yield cholesterol. Cholesterol then becomes a branch point, serving as the common precursor from which all other steroids are derived. 

The main endogenous mineralocorticoid is aldosterone, which is mainly produced by the outer layer of the adrenal medulla, the zonaglomerulosa. Aldostorone, like other steroids, binds to a specific intracellular (nuclear) receptor, the mineralocorticoid receptor (MR). Its main action is to increase sodium reabsotption by an action on the distal tubules in the kidney, which is accompanied by an increased excretion of potassium and hydrogen ions. 

After heating the chromatogram was immersed in a solution of 2 ml TWton X-100 in 5 ml chloroform plus 35 ml n-hexane in order to intensify the fluorescence and then dried in a stream of cold air. This brought about an appreciable increase in the fluorescence intensity of dienestrol and diethylsilbestrol, while the intensities of the other steroids were only marginally increased (Fig. 1). 

The effects of progesterone and several other steroids delivered from a collagen matrix as a means for preventing allograift skin rejection in mice and rats was reported (55). Results showed that the half-life of both progesterone and estradiol preparations was about 7 days, and about 90% of all steroid present was absorbed in 15—30 days. 

The lipids of major physiologic significance are fatty acids and their esters, together with cholesterol and other steroids. 

Cholesterol, an amphipathic lipid, is an important component of membranes. It is the parent molecule from which all other steroids in the body, including major hormones such as the adrenocortical and sex hormones, D vitamins, and bile acids, are synthesized. 

Cholesterol is the precursor of all other steroids in the body, eg, corticosteroids, sex hormones, bile... 

The ceUular source of the various ovarian steroids has been difficult to unravel, but a transfer of substrates between two cell types is involved. Theca cells are the source of androstenedione and testosterone. These are converted by the aromatase enzyme in granulosa cells to estrone and estradiol, respectively. Progesterone, a precursor for all steroid hormones, is produced and secreted by the corpus luteum as an end-product hormone because these cells do not contain the enzymes necessary to convert progesterone ro other steroid hormones (Figure 42-8). 

Synthesis of tatty acids, cholesterol, and other steroids, metabolic detoxification of drugs, poisons, end NHa... 

The mechanisms of corticosteroid receptor regulation of transcription have been elucidated. Both type I and type II corticosteroid receptors are members of a superfamily of ligand-activated transcription factors defined by protein sequence similarity. Included in this superfamily are various other steroid receptors, such as the estrogen receptor, as well as members of the retinoic acid receptor... 

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