Evolution of mammalian endothermic metabolism: leaky membranes as a source of heat
O/sub 2/ consumption was measured at 37/degrees/C in tissue slices of liver, kidney, and brain from Amphilbolurus vitticeps and Rattus norvegicus (a reptile and mammal with same weight and body temperature) both in the presence and absence of ouabain. O/sub 2/ consumption of the mammalian tissues was two to four times that of the reptilian tissues and the mammalian tissues used three to six times the energy for Na/sup +/-K/sup +/ transport than the reptilian tissues. Passive permeability to /sup 42/K/sup +/ was measured at 37/degrees/C in liver and kidney slices, and passive permeability to /sup 22/Na/sup +/ was measured at 37/degrees/C in isolated and cultured liver cells from each species. The mammalian cell membrane was severalfold leakier to both these ions than was the reptilian cell membrane, and thus the membrane pumps must use more energy to maintain the transmembrane ion gradients. It is postulated that this is a general difference between the cells of ectotherms and endotherms and thus partly explains the much higher levels of metabolism found in endothermic mammals.
- Research Organization:
- Univ. of Wollongong, New South Wales (Australia)
- OSTI ID:
- 6145808
- Journal Information:
- Am. J. Physiol.; (United States), Vol. 253:1
- Country of Publication:
- United States
- Language:
- English
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CELL MEMBRANES
PERMEABILITY
OXYGEN
METABOLISM
POTASSIUM 42
MEMBRANE TRANSPORT
SODIUM 22
BIOLOGICAL EVOLUTION
BODY TEMPERATURE
BRAIN
CATIONS
KIDNEYS
LIVER
LIZARDS
OUABAIN
POTASSIUM COMPOUNDS
RATS
SODIUM COMPOUNDS
ALKALI METAL COMPOUNDS
ALKALI METAL ISOTOPES
ANIMALS
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
BETA-PLUS DECAY RADIOISOTOPES
BODY
CARBOHYDRATES
CARDIAC GLYCOSIDES
CARDIOTONICS
CARDIOVASCULAR AGENTS
CELL CONSTITUENTS
CENTRAL NERVOUS SYSTEM
CHARGED PARTICLES
DIGESTIVE SYSTEM
DRUGS
ELEMENTS
GLANDS
GLYCOSIDES
HOURS LIVING RADIOISOTOPES
INTERMEDIATE MASS NUCLEI
IONS
ISOTOPES
LIGHT NUCLEI
MAMMALS
MEMBRANES
NERVOUS SYSTEM
NONMETALS
NUCLEI
ODD-ODD NUCLEI
ORGANIC COMPOUNDS
ORGANS
POTASSIUM ISOTOPES
RADIOISOTOPES
REPTILES
RODENTS
SODIUM ISOTOPES
STROPHANTHINS
VERTEBRATES
YEARS LIVING RADIOISOTOPES
551001* - Physiological Systems- Tracer Techniques