This may be the reason that a-tocopherol and total tocopherol in yolk and liver decreased as vitamin A levels increased; however, d-tocopherol in yolk and c- and d-tocopherol in liver linearly increased with increasing vitamin A levels. These results suggest that we should consider the reduced biological activity and anti-sterility activity caused by a-tocopherol, and improved antioxidant effects caused by d-tocopherol, when the diet is supplemented with higher level of vitamin A. High levels of dietary vitamin A also resulted in congenital malformations during embryonic development. Excessive supplementation with vitamin A might increase bone fracture risk by depleting vitamin D. Vitamin D receptor, the transport protein of vitamin D, plays an important role in the absorption of vitamin D. The current study showed that excessive levels of vitamin A increased mRNA expression of vitamin D receptor, which might be a compensatory mechanism for poor vitamin D absorption at the molecular level. In the current study, yolk color was linearly decreased by increased dietary vitamin A. Yolk color is mainly affected by a large component of yellow, fat-soluble pigments, such as carotenes, b-carotene, and xanthophylls. The absorption of these fat-soluble pigments, like the absorption of fat-soluble vitamins, might be reduced by a high intake of vitamin A,. The classical renin-angiotensin system was initially characterized as a major regulator of systemic blood pressure and fluid and electrolyte balance by way of direct vasoconstriction of vascular smooth muscle, generalized sympathetic nervous system activation, and mediation of aldosterone and epinephrine release. The RAS is presently known to be comprised of circulating angiotensins and independent tissue-specific RASs. Prominent among tissue-specific RASs is the brain RAS. Angiotensin II, the main effector peptide of the RAS, is abundantly expressed in the brain. There are two primary G protein-coupled receptors for Ang II reported to be present in the brain: type 1 and type 2. The AT1 receptor mediates the classical functions noted above along with thirst and sodium chloride appetite. This receptor may also be associated with diabetes, depression, Parkinson’s disease, and Alzheimer’s disease. The AT2 receptor is believed to act antagonistically to the AT1 receptor by mediating vasodilation and cerebroprotection, as well as neural differentiation, regeneration, and neurotrophic actions. There are several biochemical pathways for the Regorafenib breakdown of Ang II into inactive peptides. Ang II can be converted to the short-lived heptapeptide Ang III by glutamyl aminopeptidaseA. Ang III is then cleaved by the membrane-bound alanyl aminopeptidase-N to form the 3–8 hexapeptide Ang IV. Further metabolism of Ang IV by aminopeptidases results in inactive peptides. Ang II can also be metabolized by a variety of mono- and di-peptidyl aminopeptidases. Alternatively, Ang II can be converted to Ang by angiotensinconverting enzyme-2, prolyl carboxypeptidase and prolyl endopeptidase, see reviews. Ang has been of particular interest lately as its actions through the G protein-coupled receptor Mas serve to counterbalance the deleterious effects of Ang II.