ENDOCRINE FUNCTIONS OF THE KIDNEY
Many substances with biological activity are synthesized in the kidney and exert either paracrine (functions of transport, metabolic conditioning, or the growth of renal cells) or systemic (endocrine). Vitamine D The active form of vitamin D [1, 25 (OH) 2– vitamin D 3 or calcitriol] is produced in proximal tubular cells from its hepatic precursor, 25 (OH) vitamin D3, under the influence of alpha-hydroxylase. This enzyme's activity is increasing. PTH released by PTH increases the activity of this enzyme... The active form of vitamin D raises digestive and renal absorption of calcium and intestinal absorption of phosphate. Erythropoietin (EPO) It is a glycoprotein produced by interstitial peritubular fibroblast cells in response to changes in partial tissue pressure of O2. In addition, EPO is produced in response to cellular hypoxia, physiological (altitude), or pathology (respiratory pathologies, for example) and stimulates the bone marrow production of red blood cells. ...