The kidney is a very important organ
Introduction
To begin to describe the general mechanism of the diuretics action, it is essential to remember the important functions that the kidney meets in general, its physiological mechanism and then address the diuretics mechanism. The kidney is a very important organ, since it fulfills diverse functions, one of the most important to maintain body homeostasis.
Developing
Microscopically the kidney consists of more than one million nephrons (functional-structural unit), these in turn are composed of two fundamental elements: renal corpuscle and renal tubule. The renal corpuscle can be divided into: Bowman capsules (surrounds the glomerulus) and glomerulus (blood capillaries where blood filtering occurs);and the renal tubule consists of: proximal contoured tubule, Henle handle, distal contoured tubule and contoured contoured tubule. Diuretics do not act directly on water, but through sodium. The diuretic action in a specific segment of the kidney will act differently depending on the diuretic that is used.
Proximal contoured tubule: the Na+ anti -transporter, H+ located in the luminar membrane will allow the entry of Na+ to the cell cytoplasm and the output of the H+ towards the light of the tubule. The H+ in the tubular light together with the HCO3 forming H2CO3, which is broken down into co₂ and h₂o by the carbonic anhydrase located on the cell edge. The CO₂ disseminates by the luminal membrane into the cell interior and inside H2CO3, by the cytoplasmic carbonic anhydra. The H2CO3 is ionized forming H+ and HCO3-. In the basolateral membrane there is a cotransporter where Na+ and HCO3- to the interstitio comes out, which displaces water to the interstitium by reabsorbing na+. The diuretics that block carbonic anhydra in the membrane and cytoplasm will not convert the H2CO3 and therefore this does not pass the cell cytoplasm and the anti -porter Na+/ H+ will not work, in this way the diuretic avoids the reabsorption of Na+ and water to the water to theinterstice.
Henle handle: descending handle is permeable to water while ascending handle is waterproof to water and reabsorbs chlorine and sodium by active transport. Here 65% of Na is reabsorbed+. The liquid that comes out of the proximal contoured tubule is connected to the descending handle and is losing water due to reabsorption of this, in this way the urine is becoming hypertonic. In the ascending handle cl- and na+ they are reabsorbed without water, so the urine is becoming hypotonic, and thus reaches the distal contoured tubule. The Na+ -K -2Cl– Cotransport existing in the upstream of Henle’s handle in the luminal membrane works by capturing electrochemical gradient of Na+ produced by the Na+ pump (atpasa -na+ /k+) that is found in the basolateral membrane.
By this collection the Na+ passes to the intracellular and interstitial space, while the K+ enters the cell, the 2cl- that enter the cell make it become negative inside and thus attract the CA+ and MG+ so that theCell keep your load. ASA diuretics inhibit the Nak2CL unidirectional cotransporter in Henle’s ascending branch. Inhibiting this, a powerful diuretic effect is achieved, the sodium chloride that is normally reabsorbed (25%) will no longer be reabsorbed and excreted by urine, if the cl- is not absorbed, the cell inside will never become negative and notwill attract Ca+ and Mg and these will go through the urine.
Distal contoured tubule and collecting tubule: The epithelial cells of the distal contoured tubule have in their luminal membrane a na+ -cl cotransporter- This uses the energy originated by the Na+ pump of the basolateral membrane, which creates an electrochemical gradient for the Na+. Enter the CL– in the cell and then leave towards the interstitium by the simporter K+Cl-. Inhibitors of the unidirectional na+ and cl- (Tiazidic) collars. (Proximal tubule constitutes a secondary action site).
At the same time, distal contoured tubule cells and collecting tube have mineralocorticoid hormonal receptors, especially aldosterone. As a consequence of these effects, conductance for the NA+ increases in the luminal membrane and the activity of the Na+ pump in the basolateral. ADH increases the permeability of the luminal membrane to the water, causing the water to disseminate in favor of the osmotic concentration and that the urine becomes hypertonic;If there is no ADH, urine will not be able to lose water and will be hypotonic.
conclusion
In the collecting and distal tubule they have in their membranes Na+ ducts causing them to enter the cell generated by the Na+ pump located in the basolateral membrane. This conveyor makes the Na+ rise in blood concentration and that K+ is decreased in blood. By inhibiting this the concentration of Na+ increases in the urine and will be excreted in greater quantity in the urine and the K+ decreases in the urine remaining in the cell by inhibition of Na channels+. ((Na+ duct inhibitors of the renal epithelium (K savings)).
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