Asphyxia of the Frog's Kidneys

Abstract

Urine formation was measured in normal frogs by repeatedly weighing individuals whose cloacae were bound for a known period of time and later unbound. It was observed that in the absence of oxygen no urine formed. Even when diuresis was favored, by subcutaneous injection of water or 1% urea solution, no urine reached the bladder. When the breathing was interrupted by appropriate pithing or anesthesia the same inhibition of urine formation occurred, provided the frogs were kept at temperatures (20° to 27°C.) high enough so that oxygen was not adequately supplied to the blood through the skin. After 2 hours of asphyxia, anuria persisted for 1 to 4 hours, until such time as the frogs resumed breathing. As the frogs recovered, extra urine was formed until the initial net body weight was reestablished. The heart's circulation was maintained throughout. Two alternatives presented themselves: did (glomerular) fluid cease to form, or was the fluid that formed completely reabsorbed (by the tubules)? If no fluid formed was the circulation inadequate, or was oxygen indispensable for the excretion of water? The exposed kidneys were examined in pithed frogs that were lying in a closed gas chamber. Blood invariably ceased to flow through the glomeruli within 1 minute after deprivation of oxygen. Often the glomeruli emptied completely of blood, and the whole kidney became paler. No corpuscles and hence presumably no plasma flowed through the glomerular capillaries until 1 minute after oxygen was again supplied to them. A relatively low concentration of oxygen was adequate to maintain glomerular circulation in the exposed kidney. Portions of the kidneys other than the glomeruli continued in the absence of oxygen to receive a copious supply of blood, and it is believed that the asphyxia exerted its peculiar effect because of the special nature of the glomerular circulation.