Activation of acid-secreting intercalated cells in rabbit collecting duct with ammonium chloride loading

Abstract

In normal rabbit, immunolabeling of intercalated cells in the outer medullary collecting duct (OMCD) demonstrates band 3-like protein in the basolateral plasma membrane (15) and H(+)-adenosinetriphosphatase (H(+)-ATPase) in the apical plasma membrane and cytoplasmic vesicles (30). However, in type A intercalated cells in the cortical collecting duct (CCD), band 3-like protein is located primarily in multivesicular bodies and cytoplasmic vesicles (15), whereas H(+)-ATPase is present in cytoplasmic vesicles only in most intercalated cells (30). In this study, we observed the effect of chronic acid loading on immunolocalization of these transporters in the collecting duct. Adult New Zealand White rabbits received either normal tap water (controls) or 75 mM NH4Cl for 12 days plus eight daily gavages of 2-6 meq NH4Cl/kg body wt. At time of death, mean urine pH of acid-loaded animals was 5.96 (SD = 0.69), vs. 8.47 (SD = 0.07) in controls. Kidneys were fixed by in vivo perfusion and processed for light and electron microscopic immunoperoxidase localization of band 3-like protein and immunogold localization of H(+)-ATPase. In controls, band 3-like protein was largely confined to multivesicular bodies in the majority of positive-staining intercalated cells in the CCD and to the basolateral plasma membrane of intercalated cells in the OMCD. In acid-loaded rabbits, band 3 protein-positive intercalated cells in the inner CCD and the in the outer stripe of the OMCD (OMCDo) were strikingly stellate in form. Basolateral plasma membrane label was intensified, while the number of labeled multivesicular bodies was diminished. Morphometric analysis demonstrated an increase in the amount of basolateral plasma membrane in these intercalated cells. In control rabbits, H(+)-ATPase immunoreactivity in intercalated cells in the CCD was located predominantly over cytoplasmic vesicles. A minority of intercalated cells exhibited basolateral plasma membrane label, and only an occasional cell displayed apical plasma membrane label. In acid-loaded rabbits, H(+)-ATPase immunoreactivity was enhanced along the apical plasma membrane of intercalated cells in the inner CCD, and morphometric analysis demonstrated increased apical plasma membrane in band 3-positive intercalated cells in this segment. These results suggest that rabbits respond to acid loading via enhancement of both electrogenic proton secretion and Cl-/HCO3- exchange in intercalated cells in the inner CCD and the OMCDo.

Acid incubation reverses the polarity of intercalated cell transporters, an effect mediated by hensin

“…In six α cells examined in four CCDs, the mean alkalinization resulting from removing bath Cl -was 0.34 ± 0.02 pH units before acid incubation and 0.47 ± 0.03 pH units after acid incubation, a 36% increase (P < 0.05). These data are consistent with increased expression of apical H + -ATPase and basolateral band 3 in α cells after chronic metabolic acidosis in vivo (7,31).…”

Normal Ultrastructure of the Kidney and Lower Urinary Tract

“…The type A intercalated cells secrete acid and reabsorb bicarbonate via the vacuolar proton pump located in the apical plasma membrane and apical cytoplasmic vesicles and a basolateral Cl-/HCO,-exchanger. Enhancement of acid secretion is achieved by insertion of proton pump-containing cytoplasmic vesicles into the apical plasma membrane and in the rabbit, by insertion of Cl-/HCO,-exchangers into the basolateral plasma membrane (53). Functional studies have demonstrated that type B intercalated cells secrete bicarbonate by apical Cl-/HC03-exchange (18,57).…”

Replication of segment-specific and intercalated cells in the mouse renal collecting system

“…Several studies aimed to identify the origin of the cellular heterogeneity of the renal CS (e.g., Satlin and Schwartz 1987;Minuth et al 1989; Fejes-Toth and Naray-Fejes-Toth 1992; Satlin et al 1992;Yasoshima et al 1992;Kim et al 1994Kim et al , 1996Verlander et al 1994;Matsumoto et al 1996;Kloth et al 1998;Schwartz 2001). Based on the morphological studies on developing rat kidneys, Madsen et al concluded that type A and non-type A IC cells develop independently from undiVerentiated cells in the CNT and the medullary CD (Kim et al 1994).…”