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Granger, D., M. Marsolais, J. Burry, and R. Laprade. Na+/H+ exchangers in the human eccrine sweat duct. Am J Physiol Cell Physiol 285: C1047-C1058, 2003. First published July 2, 2003; 10.1152/ajpcell.00581.2002.--Using an anti-NHE1 antibody, we demonstrate the presence of a [Na.sup.+]/[H.sup.+] exchanger of isoform 1 (NHE1) in the human eccrine sweat duct. A strong staining was observed at the basolateral membrane of the outer cell layer ([NHE1.sub.basal]), at the junction between inner and outer cells layers ([NHE1.sub.inter]), and along the lateral membranes ([NHE1.sub.later]) of all cells of the duct. At the luminal membrane, no staining was demonstrated either for NHE1 or NHE3. To investigate [Na.sup.+]/[H.sup.+] mediated proton transport, straight sweat duct portions were isolated and perfused in vitro under HC[O.sup.-.sub.3]-free conditions. In the presence of basolateral 5-ethyl-N-isopropyl amiloride (EIPA), an acidification of 0.29[+ or -]0.03 pH units was observed, whereas no effect was observed with luminal EIPA. Bath sodium removal generated a stronger acidification (0.41[+ or -]0.09 pH units). Removal of luminal sodium (in the absence or presence of basolateral EIPA), or low luminal chloride, led to an alkalinization, presumably due to a decrease in intracellular sodium, strongly suggesting functional activity of NHE[1.sub.inter]. We therefore conclude that in the sweat duct, NHE1 plays a major role in intracellular pH regulation. 5-ethyl-N-isopropyl amiloride; chloride; intracellular pH measurements; immunolocalization; epithelial cells

We investigated for the presence of a vacuolar-type [H.sup.+]-ATPase (V-ATPase) in the human eccrine sweat duct (SD). With the use of immunocytochemistry, an anti-V-ATPase antibody showed a strong staining at the apical membrane and a weaker one in the cytoplasm. Cold preservation followed by rewarming did not alter this staining pattern. With the use of the pH-sensitive dye 2',7'-bis(2-carboxyethyl)-5(6)-carboxyfluorescein on isolated and perfused straight SD under HC[O.sup.-.sub.3]-free conditions and in the absence of [Na.sup.+], proton extrusion was determined from the recovery rate of intracellular pH (dp[H.sub.i]/dt) following an acid load. Oligomycin (25 [micro]M), an inhibitor of F-type ATPases, decreased dp[H.sub.i]/dt by 88 [+ or -] 6%, suggesting a role for an ATP-dependent process involved in p[H.sub.i] recovery. Moreover, dp[H.sub.i]/dt was inhibited at 95 [+ or -] 3% by 100 nM luminal concanamycin A, a specific inhibitor of V-ATPases, whereas 10 [micro]M bafilomycin [A.sub.1], another specific inhibitor of V-ATPases, was required to decrease dp[H.sub.i]/dt by 73%. These results strongly suggest that a V-ATPase is involved in proton secretion in the human eccrine SD. proton pump; intracellular pH measurement; concanamycin A; bafilomycin [A.sub.1]; oligomycin

A study was conducted on the function of the third domain of Bacillus thuringiensis insecticidal toxin CryIAa in membrane permeabilization under a receptor-free environment. Mutants were developed by replacing arginine with glutamine, lysine, histidine and glutamic acid. Results demonstrate the functional role of domain II and indicates that domain I interacts with the residues of the positive arginine face of block 4.

Adenosine triphosphate acts as transducing agent in linking sodium pump activities to the potassium conductance in renal proximal tubule. The accumulated sodium is actively transported out of the cell and potassium is pumped in resulting in ventsorption of glucose and amino acids by the renal proximal tube.

The effect of sodium (Na+) pump inhibitionon basolateral pottassium (K+) channel stimulated by apical Na+ entry. An adenosine triphosphate(ATP)-sensitive K+ channel on the basolateral membrane of rabbit proximal convoluted tubule was identified. The activity of this channel was observed to be stimulated by diazoxide and inhibited by strophanthidin. Data gathered suggest that this basolateral membrane K+ channel is ATP-mediated.

The effect of hydrogen-adenosine triphosphatase (H+-ATPase) bafilomycin A1 on ATP metabolism in proximal tubules were studied from dietary metabolic ashes of canines, rabbits and hamsters. Results demonstrate significant differences in the metabolic costs of bafilomycin-sensitive proton secretion by H+-ATPase between different animal species. The H+ pump in dogs required 29-44% of the energy demand of the proximal tubules while the requirements in rabbits and hamsters were lower. H+-ATPase activity of dogs, on the other hand, was lower compared to rabbits and hamsters.