1-25 dihydrocholecalciferol is formed in which of the following organs ?
(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* Leiner's 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. Ca++/Mg++ ATPase* Phospholipase A2* Ca++/phospholipids 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 apparatus*Factors 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
Liver
Kidney
Intestine
Bone