Biochemistry of kidneys

Biochemical processes in the kidneys can be divided into three groups: active processes of the formation of urine formation of ammonia and the selection of substances with hormone-like effects.
The formation of urine in the body consists of a passive process, when any foreign substances or products of metabolism by diffusion through the concentration gradient through the walls of the renal tubules, and active processes when this happens against a concentration gradient. These processes often involve. So, the active reabsorption of positively charged sodium ion of tubular fluid in blood is accompanied passive transport negative chlorine-ion, and after them and water. Active migration of substances through the walls of the renal tubules involve expenditure of energy, the source of which (as in the rest of the body) is mainly oxidative phosphorylation.
Instead part reabsorbiruetsa of sodium ions in tubular fluid moving ions potassium and hydrogen ions produced in the dissociation of carbonic acid.
The reabsorption of water occurs in two stages: at the start and end distal parts of the renal tubules. In the distal parts of tubules cellular elements joined together hyaluronic acid, which forms a waterproof membrane; under the influence of the enzyme hyaluronidase this acid fast depolimerizuet, resulting in renal wall becomes permeable to water, and she reabsorbed. Hyaluronidase in turn activates antidiuretic pituitary hormone (vasopressin), which thus prevents the water excretion with urine.
Active migration of sodium in the number of other factors is governed by the system of the renin - angiotensin. The renin - protein synthesized by special cells in the cortical layer of the kidneys, it has enzymatic activity, and is very close to the hormones. Acting on the protein beta-globulin fraction of plasma (angiotensinogen), renin it from him peptide angiotensin, which promotes the retention of sodium in the body by direct effect on the kidneys, and by stimulating the secretion of aldosterone.
Kidney produces ammonia, which will neutralize generated in the process of metabolism acid and this contributes to the maintenance of acid-base balance (see) in the body. Small amounts of ammonia is formed by oxidative deamination danilovoy acids and amino acids, but his main source of glutamine, which is delivered to the kidney with blood. The role of the kidney in maintaining acid-base balance is very significant.