Friday, February 19, 2010

Tubule Reabsorption

Reabsorption of glucose occurs in proximal convoluted tubule. Here, all that useful glucose, aminoacids, bicarbonate, and water are reabsorbed from the ultra-filtrate and put back into the blood. If the glucose were not absorbed it would end up in your urine. This happens in people who are suffering from diabetes.

Reabsorption of sodium and chloride takes place in the distal convoluted tubule of the nephron. Sodium absorption by the distal tubule is mediated by the hormone aldosterone, which is secreted by the adrenal gland. Aldosterone increases reabsorption of sodium (Na) and water, making the tubule secrete potassium (K+). Sodium and chloride (salt) reabsorption is also mediated by a group of kinases called WNK kinases.

The kidney distant tubule also reabsorbs calcium (Ca2+) in response to parathyroid hormone, taking part in calcium level regulation. PTH effect is mediated through phosphorylation of regulatory proteins and enhancing the synthesis of all transporters within the distal convoluted tubule. In the presence of parathyroid hormone, the distal convoluted tubule reabsorbs more calcium and excretes more phosphate. When aldosterone is present, more sodium is reabsorbed and more potassium excreted.