Cells of the zona fasciculata and zona reticularis lack aldosterone synthase (CYP11B2) that converts corticosterone to aldosterone, and thus these tissues produce only the weak mineralocorticoid corticosterone. However, both these zones do contain the CYP17A1 missing in zona glomerulosa and thus produce the major glucocorticoid, cortisol. Zona fasciculata and zona reticularis cells also contain CYP17A1, whose 17,20-lyase activity is responsible for producing the androgens, dehydroepiandosterone (DHEA) and androstenedione. Thus, fasciculata and reticularis cells can make corticosteroids and the adrenal androgens, but not aldosterone.
Evidence is presented that the induction of specific proteins in the chick oviduct by the steroid hormones estrogen and progesterone, involves a primary effect at the level of gene transcription. The intracellular levels of mRNA's which code for the synthesis of the egg-white proteins, ovalbumin and avidin, have been quantitated in a heterologous protein synthesizing system. It is demonstrated that these levels are directly dependent upon the inducing steroid, estrogen or progesterone, respectively. Ovalbumin mRNA has been purified to apparent homogeneity. This ovalbumin mRNA was then used as a template for the synthesis of a complementary DNA copy catalyzed by the enzyme reverse transcriptase which was isolated from avian myeloblastosis virus. This radioactively labeled complementary DNA was used to demonstrate, by means of DNA excess hybridization, that the ovalbumin gene is represented only once in each haploid genome of the chick cell. Next the complementary DNA copy of the ovalbumin mRNA was used as a genetic probe to determine the precise number of sequences of ovalbumin mRNA present at any one time after the administration of estrogen. It was demonstrated that the unstimulated chick contained no sequences of ovalbumin mRNA. Within a very short period of time after estrogen is administered the ovalbumin sequences begin to appear and reach a steady state level of 140,000 molecules per tubular gland cell. It could also be calculated that each ovalbumin molecule is probably translated some 50,000 times during its life which explains why ovalbumin comprises some 60% of the total protein in the oviduct cell. Following withdrawal of the oviduct from estrogen treatment, ovalbumin mRNA sequences again drop to undetectable levels. However, following a single injection of estrogen to these withdrawn animals, new ovalbumin mRNA sequences could be detected within 30 minutes. These data suggest that estrogen controls the activity of the ovalbumin gene via a pure transcriptional control mechanism. It is also demonstrated that the efficiency of the complementary DNA as a means of quantitating specific mRNA sequences is some 1,000 times more sensitive than the best available in vitro translation system. Finally, the efficacy of four popular translation systems is compared. It is suggested that for initial studies involving hormonal control of mRNA levels, the translation system derived from wheat germ is the simplest and most sensitive.
While tremendously beneficial to the cutting phase and often considered essential to competitive bodybuilders during contest prep, Trenbolone Acetate is also a phenomenal off-season bulking steroid . When we refer to this hormonal compound as versatile, that is truly an accurate statement. There are very few anabolic steroids that can promote mass like Trenbolone Acetate. More importantly, the effects of Trenbolone Acetate in this regard are not only strong but are far cleaner than most traditional bulking steroids. This hormone will not and cannot promote water retention, meaning each and every pound of weight gained due to use will be lean muscle mass. Of equal importance will be this steroid’s ability to help the individual control fat gain during a period of growth. To achieve true growth, this will require total caloric intake to be slightly above maintenance levels. How far above will vary from one man to the next, and while many often take it too far, this phase will still require a slight surplus. Unfortunately, this necessary surplus will promote body fat gains but due to the metabolic factors that surround Trenbolone Acetate they will be minimized. This is not a license to eat like there’s no end in sight, you can still gain a lot of fat if you continually gorge but you should be able to make better use of your total caloric intake. Those who supplement with Trenbolone Acetate during off-season periods of growth should gain less body fat than they would have without it.