<prompt> 1-25 dihydrocholecalciferol is formed in which of the following organs ?LiverKidneyIntestineBone  <response>: Kidney 470-Harper 28th 157-Rana shinde 7th Calcitriol 1.25 DHCC is the biologically active form of vitamin D. It regulates the plasma levels of calcium and phosphate, calciotropic hormone, while cholecalciferol is prohormone, synthesized in liver and kidney Biologically active form of vitamin D calcitriol is produced in the kidney 127-U.Satyanarayan 3rd Calcitriol action is similar to steroid hormone. It binds to a receptor in the cytosol and the complex acts on DNA to stimulate the synthesis of calcium binding protein Actinomycin D inhibits the action of calcitriol Calcitriol synthesis is self regulated by a feed back mechanism i.e. calcitriol decreases its own synthesis CRF requires the oral administration of 1.25 DHCCImportant Points 25 - OH - D3 Calcidol is the major storage form of vitamin in Liver Vitamin E - is the major lipid soluble antioxidant in cell membranes and lipoproteins, Does not have a precisely defined-metabolic function. Antisterility vitamin, Least toxic, It protects the polyunsaturated fatty acids PUFA from peroxidation reactions Therapeutic uses of vitamin E - Nocturnal muscle cramps, Intermittent claudication, Fibrocystic breast disease, Atherosclerosis Megadoses of niacin are useful in the treatment of hyperlipidemia Para aminobenzoic acid PABA may be regarded as a vitamin in another vitamin Folic acid Pellagra is more common in person whose staple diet is maize Leiners disease erythroderma desquamativum or exfoliative dermatitis is caused by deficiency of vitamin Biotin B7 Multiple carboxylase deficiency results from a defect in the ability to link biotin to carboxylases or to remove it from carboxylases during their degradation. Treatment is biotin supplementation Vitamin K is essential for clot formation, decreases coagulation time and is present in low concentration in milk, fat soluble Ionized calcium is the physiologically active form of calciumEnzymes regulated by calcium Calmodulin Adenylate cyclase Guanylate cyclase Ca dependant protein kinase NAD kinase. CaMg ATPase Phospholipase A2 Caphospholipids dependant protein kinase Phosphoprotein phosphatase 2B Cyclic nucleotide phosphodiesterase Pyruvate carboxylase Glycerol 3 phosphate dehydrogenase Pyruvate dehydrgenase Glycogen synthase Pyruvate kinase Inositol triphosphate acts to increase the release of Ca from endoplasmic reticulum Kidneys produces three hormones - 1, 25 DHCC Renin and Erythropoietin Renin is secreted by JG cells of the Juxta glomerular apparatusFactors that affect renin secretionStimulatoryInhibitory Increased sympathetic activity via renal nerve Increased circulating calecholamines Prostaglandins Increased Na and Cf reabsorption across macula densa Increased afferent arteriolar pressure Angiotensin IIPart - III: One or more than one options are correct out of five given alternatives 