The trimethoprim portion acts to prevent potassium excretion in the distal tubule of the nephron. The filtrate then enters the renal tubule of the nephron. It is found between afferent arteriole and the distal convoluted tubule of the same nephron. Thiazide diuretics also increase calcium reabsorption at the distal tubule. Fluid in the filtrate entering the proximal convoluted tubule is reabsorbed into the peritubular capillaries. Atrial natriuretic peptide causes the distal convoluted tubule to secrete more sodium. Amino acids are reabsorbed by sodium dependent transporters in the proximal tubule. The ascending limb drains urine into the distal convoluted tubule. This hypotonic filtrate is passed to the distal convoluted tubule in the renal cortex. Glucose at normal plasma levels is completely reabsorbed in the proximal tubule. The mechanism of diuresis involves the proximal tubule of the kidney. Aldosterone serves to retain sodium from the distal renal tubule. Water is 55% reabsorbed in the proximal tubule. These all are secreted into the lumen of renal tubule. In addition there is a direct toxicity to the proximal renal tubule.