General Pharmacology [diuretics ]
General Pharmacology Renal handling of sodium and water To understand the action of diuretics, it is first necessary to review how the kidney filters fluid and forms urine. The following discussion and accompanying illustration provide a simple overview of how the kidney handles water and electrolytes. For more detailed explanation, particularly related to ion and fluid movement across the renal tubular cells, the reader should consult a physiology textbook. As blood flows through the kidney, it passes into glomerular capillaries located within the cortex (outer zone of the kidney). These glomerular capillaries are highly permeable to water and electrolytes. Glomerular capillary hydrostatic pressure drives (filters) water and electrolytes into Bowman's space and into the proximal convoluting tubule (PCT). About 20% of the plasma that enters the glomerular capillaries is filtered (termed filtration fraction). The PCT, which lies within the cortex , is the site of sodium, water an...