Cellular mechanisms of urinary acidification.

Active H+ transport in the turtle urinary bladder. Coupling of transport to glucose oxidation.

“…Provided that the pump is not "saturated," this increase in availability will result in a stimulation of the active transport rate. This situation is analogous to the mechanism of stimulation of active H + transport by increasing the ambient pCO2 (23,27,28). The higher the flow through the shunt pathway, the more the H + pump will be stimulated and the greater willJ~o, be.…”

“…H + secretion is stimulated by the presence of ambient CO2 and is dependent on the activity of carbonic anhydrase in the epithelial cell (22,23). It is inhibited by anoxia and by metabolic inhibitors (28) and is stimulated by the hormone aldosterone (3).…”

Intracellular pH regulation in rabbit renal medullary collecting duct cells. Role of chloride-bicarbonate exchange.

“…Volume regulation in response to hypertonic stimuli has recently been shown to be mediated by Cl/HCO3 exchange coupled to Na/H exchange in mouse thick ascending limb (23) and amphibian gall bladder (24). In epithelial cells specialized to secrete luminal acid, basolateral Cl/HCO3 exchange functions to restore intracellular pH by secreting into the basolateral space alkali equivalents generated by the luminal secretion ofacid (25). Such acid-secreting epithelia include gastric mucosa (26), amphibian bladder (27), and MCD (5).…”

“…Their viability has been confirmed by measurement of 02 consumption, ATP levels, and the demonstration of pHi regulation (3). In the cortical collecting duct and the turtle bladder, acid secretion is thought to occur only via the intercalated cells (7,25). Because of the striking morphologic differences between principal cells in the inner stripe and in the cortex (29), it is impossible to assign functions to inner stripe collecting duct cell types based on analogy to these other tissues.…”

“…The stilbenes, SITS and DIDS, are relatively specific and potent inhibitors of red blood cell anion exchange (15). Sensitivity to these inhibitors has been demonstrated for turtle bladder (25) and MCD bicarbonate transport (5), in Necturus gall bladder (21) and proximal tubule (32), and also in mammalian proximal tubule (36) and thick ascending limb (20). In all of these studies, stilbene concentrations of l0-4 M or higher were used.…”