Vanadate inhibition of ATP-dependent H+ transport in membrane vesicles from turtle bladder epithelial cells

Characteristics of the isolated apical plasmalemma and intracellular tubulovesicles of the gastric acid secreting cells: demonstration of secretagogue-induced membrane mobilization

“…In the latter species, a histamine-induced mobilization of the tubulovesicular membranes and a consequent increase in the population of secretory plasmalemma were also demonstrated to occur. The present approach, thus, opens up the possibility of future studies on membrane migration in other sytems (Stanton et al, 1981;Karnieli et al, 1981; Lewis & deMoura, 1982;Madson & Tisches, 1983;Gluck et al, 1982;Wade, 1986;Youmans & Brodsky, 1987) where an analogous membrane trafficking has been suggested to occur during secretory events.…”

“…It may be noted that the Mg2+-ATPase activity of the purified turtle bladder membrane vesicles, capable of generating a pH gradient and implicated to be involved in urinary acidification, has recently been resolved into two different types based on their differential sensitivity toward vanadate and A-ethylmaleimide (Youmans & Brodsky, 1987). Additional evidence for the presence of two forms of (H+,K+)-ATPase is based on their responses to micromolar Ca2+.…”

Ouabain-insensitive K-adenosine triphosphatase in distal nephron segments of the rabbit.

“…Note that a K-activated ATPase, insensitive to ouabain and sensitive to inhibition by vanadate, has also been isolated from the brush border membranes of the rabbit descending colon epithelium (17). Furthermore, a vanadate-sensitive ATPase activity has also been reported to be present in the turtle bladder epithelial cells (18). The physiological functions of the vanadate-sensitive (and ouabain insensitive) ATPases in the kidney, descending colon, or turtle bladder have not been established.…”

In vivo environmental temperature and the in vitro pattern of luminal acidification in turtle bladders. Evidence for HCO3 ion reabsorption.

“…A bicarbonate pump (as well as a proton pump) could be responsible for generating the ATP-induced acidification process found in isolated membrane vesicles obtained from turtle bladder epithelial cells, even though these vesicles had been prepared and incubated in media devoid of exogenously added HCO 3 and CO 2 (Gluck et al, 1982;Youmans et al, 1983;Youmans and Brodsky, 1987). This is because all of the media used had been exposed to atmospheric air, the pCO 2 of which is 0.3 mmHG at 25~ Therefore, the dissolved CO 2 in the extravesicular compartment of such media must have reached a level of 13 #M (in keeping with Henry's law), and the same level (13 #M) must have been reached in the intravesicuiar fluid (owing to the CO~ permeability of vesicular membranes).…”