Mechanisms of proximal proton secretion in BBM of herbivorous, omnivorous, and carnivorous species.
The mechanisms of proton secretion by the proximal brush-border membrane (BBM) were compared in carnivorous (dog), omnivorous (human, pig, rat), and herbivorous (rabbit, hamster) species. The activity of the proton pump (V-type bafilomycin-sensitive H(+)-adenosinetriphosphatase) and of the Na+/H+ exchanger (amiloride-sensitive quenching of acridine orange fluorescence), the two major proton secretion mechanisms, was measured. The enzymatic activity of the H(+)-adenosinetriphosphatase activity was measured in intact (endosomes) and solubilized (0.1% deoxycholate or Triton X-100) BBM vesicles isolated by conventional Mg2+ precipitation techniques. In all species, but not in humans, the fraction of the ATP turnover energizing the proton pump (bafilomycin-sensitive respiration) was also measured in isolated proximal tubules. Significant differences in acid transport mechanisms were noted between species, with the proton pump predominating in the BBM of carnivorous species and the Na+/H+ exchanger predominating in the BBM of herbivorous species. The fraction of respiration suppressible by bafilomycin in proximal tubules was also different in all the species considered. This may indicate a different organization of proximal H+ transport related to the species-specific menace to acid-base balance.
Duplain
M
M
Nephrology Service, Hôpital Notre-Dame de Montréal, Québec, Canada.
Noel
J
J
Fleser
A
A
Marshansky
V
V
Gougoux
A
A
Vinay
P
P
D000818:Animals; D006224:Cricetinae; D004285:Dogs; D007668:Kidney / Q000378:metabolism*; D007684:Kidney Tubules / Q000378:metabolism; D008871:Microvilli / Q000378:metabolism; D010101:Oxygen Consumption; D017494:Proton Pumps / Q000378:metabolism; D006180:Proton-Translocating ATPases / Q000378:metabolism; D011522:Protons; D011817:Rabbits; D051381:Rats; D017208:Rats, Wistar; D017923:Sodium-Hydrogen Exchangers / Q000378:metabolism; D013045:Species Specificity; D013552:Swine
D017494:Proton Pumps; D011522:Protons; D017923:Sodium-Hydrogen Exchangers; D006180:Proton-Translocating ATPases