DNA is also subject to attack from reactive oxygen species (e.g., O2- , H2O2, and OH†). These potent oxidizing agents are generated by ionizing radiation and by chemical agents that generate free radicals. Oxidation of guanine, for example, generates 7,8-dihydro-8-oxoguanine, or oxoG. 

TLS Online TPP Program

#Id: 5553

#Unit 7. System Physiology – Animal

Intercalated cells play a major role in acid-base regulation and constitute 30 to 40 percent of the cells in the collecting tubules and collecting ducts

TLS Online TPP Program

#Id: 5554

#Unit 7. System Physiology – Animal

There are two types of intercalated cells: type A and type B

TLS Online TPP Program

#Id: 5555

#Unit 7. System Physiology – Animal

Type A intercalated cells  secrete hydrogen ions by a hydrogen-ATPase transporter and by a hydrogen-potassium-ATPase transporter are especially important in eliminating hydrogen ions while reabsorbing bicarbonate in acidosis

TLS Online TPP Program

#Id: 5556

#Unit 7. System Physiology – Animal

Type B intercalated cells have functions opposite to those of type A cells and secrete bicarbonate into the tubular lumen while reabsorbing hydrogen ions in alkalosis

TLS Online TPP Program

#Id: 5557

#Unit 7. System Physiology – Animal

The changes in osmolality and volume in the collecting ducts depend on the amount of vasopressin acting on the ducts.

TLS Online TPP Program

#Id: 5558

#Unit 7. System Physiology – Animal

The key to the action of vasopressin on the collecting ducts is aquaporin-2 & stored in vesicles in the cytoplasm of principal cells