Steroid, acids adrenocortical

Cholesterol is probably the best known steroid because of its association with atherosclerosis. However, biochemically it is also of significance because it is the precursor of a large number of equally important steroids that include the bile acids, adrenocortical hormones, sex hormones, D vitamins, cardiac glycosides, sitosterols of the plant kingdom, and some alkaloids. 

Steroids Cholesterol, Adrenocortical, Bile Acids Ergosterol, Agnosterol, Desmosterol 2,30... 

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. 

Adrenocortical Steroids, Determination of Individual (Neher), 1, 127 Amino Aciduria (Bigwood, Crokaert, Schram, Soupart and Vis), 2, 201 Ammonia, Blood (Bessman), 2, 135 Ascorbic Acid in Man and Animals (Knox and Goswami), 4, 122 Automation (Marsh), 2, 201 Bile Pigments in Jaundice (Billing), 2, 268... 

We first describe the biosynthesis of fatty acids, the primary components of both triacylglycerols and phospholipids, then examine the assembly of fatty acids into triacylglycerols and the simpler membrane phospholipids. Finally, we consider the synthesis of cholesterol, a component of some membranes and the precursor of steroids such as the bile acids, sex hormones, and adrenocortical hormones. 

Ascorbic acid may be required for steroid hormone biosynthesis depleted from adrenal cortex on cortical secretion Biotin adrenocortical insufficiency noted in biotin deficiency... 

Because all known therapeutic effects ofACTH can be achieved with corticosteroids, synthetic steroid hormones generally are used therapeutically instead ofACTH. A synthetic derivative of ACTH comprised of the first 24 amino acids of the natural hormone, cosyntropin ( cortrosyn, syn-acthen), is used principally in the diagnostic assessment of the HPA axis. In the standard cosyntropin test, cosyntropin is used at the considerably supraphysiological dose of 250 pg to maximally stimulate adrenocortical steroidogenesis. Cosyntropin is readily absorbed from... 

Another method that has been used to measure the excretion of adrenal steroids is the determination of formaldehydogenic steroids in the urine. This is no longer considered a reliable method of chemical assay and bears no certain relation to adrenocortical function (Marrian, 1952) nevertheless, it is worth reviewing the results obtained by this method in human scurvy. When ascorbic acid was administered to three patients with scurvy, instead of the expected increase in the excretion of formalde-hydogenic hormones, there was a fall in their excretion lasting several days (Daughaday et al., 1948). 

With the development of knowledge concerning the role of pantothenic acid in intermediary metabolism, the critical importance of this vitamin to adrenocortical function becomes more understandable. When the adrenal cortex is stimulated by stressful situations, its function is to respond rapidly by secreting steroid hormones which initiate and maintain a variety of physiological reactions. Its ability to synthesize these hormones may depend on its capacity to mobilize energy rapidly. Pantothenic acid, as part of coenzyme A, plays a critical role in the oxidative metabolism of both carbohydrate and fatty acids and may also be involved directly in lipid synthesis. Therefore, a deficiency in pantothenic acid can create a situation in which the ability of the adrenocortical cells to secrete steroid hormones is seriously impaired. 

Adrenocortical hormones, see also under Adrenocortical steroids and under names of individual hormones activity, VII, 294 IX, 163ff. assay of, IX, 162, 175 criteria of, IX, 165-168 unit of, IX, 162, 164 anoxic anoxia and secretion of, X, 119 ascorbic acid and, IX, 178,199 X, 107, 108-111... 

At variance with the decrea.sed release of free fatty acid by mesenteric and epididymal adipose tissue from fasted or semifasted adrenalectomized rats (Reshef and Shapiro, 1960 Schotz et cd., 1959) and the in vitro effects of adrenocortical steroids (Jeanrenaud and Renold, 1960) is the report of Levy and Ramey (1959). These workers measured the extractable lipid in the epididymal fat pads of rats before and after a 12-hour fast they reported that the loss of lipid from the adipose ti.ssue stores of adrenalectomized rats exceeds that from normal rats. They further observed that the prior... 

Rashef and Shapiro (1960) reported that pretreatment of adrenalecto-mizc d rats with either epinephrine or eortisone inereased the depressed rate of free fatty acid release by their mesenteric adipose tissue in vitro however, maximal effects were, obtained only when both were given. It was further pointed out that epinephrine alone was highly effective in restorii the depressed rate of free fatty acid release by tissue from adrenal demedul-lated rats. Reshef and Shapiro (1960) also observed that pretreatment of starved intact rats with cortisone had little effect on the release of free fatty acid by mesenteric adipose tissue. Such treatment, however, inereased and prolonged the response of tissue removed from rats injected with epinephrine (sec Section VI, A). These results may reflect in part the effects of glucocorticoid administration on the adipose tissue stores of the intact animal, but the interesting relation between the effects of epinephrine and adrenocortical steroids on the release of free fatty acids deserves further study. 

The lipid fractions obtained from plants and animals contain another important group of compounds known as steroids. Steroids are important biological regulators that nearly always show dramatic physiological effects when they are administered to living organisms. Among these important compounds are male and female sex hormones, adrenocortical hormones, D vitamins, the bile acids, and certain cardiac poisons. 

Compounds with steroid structures, such as adrenocortical hormones, sex hormones, cholesterol and bile acids, occupy a central position... 

The release of arachidonic acid is stimulated in response to trauma (tissue damage). It is believed that the anti-inflammatory effects of adrenocortical steroids derive from their ability to suppress the enzymes that cause the release of arachidonic acid, thereby preventing the biosynthesis of prostaglandins. 

Steroids. Although they do not often contain fatty acids the steroids are frequently classed as lipids on account of their occurrence in natural fats and their solubility characteristics. They include cholesterol and the sex and adrenocortical hormones. 

Cholesterol is readily synthesized from acetyl-CoA (page 231) and is the parent substance for the other natural steroids these include cholic acid which is a constituent of the bile salts, the sex hormones and the adrenocortical hormones. In addition, a derivative of cholesterol, namely 7-dehydrocholesterol, is present in the skin and this, on irradiation with ultraviolet light, is converted to vitamin D which is a steroid derivative (page 156). 

Among the most abundant steroids, cholesterol is present in almost all human and animal tissue (Real Life 4-2). Bile acids are produced in the liver as part of a fluid delivered to the duodenum to aid in the emulsification, digestion, and absorption of fats. An example is cholic acid. Cortisone, used extensively in the treatment of rheumatoid inflammations, is one of the adrenocortical hormones produced by the outer part (cortex) of the adrenal glands. These hormones participate in regulating the electrolyte and water balance in the body, as well as in protein and carbohydrate metabolism. 

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