AJP - Renal Physiology, Vol 257, Issue 3 486-F501, Copyright © 1989 by American Physiological Society

ARTICLES

Development of H+ secretion by cultured renal inner medullary collecting duct cells

L. P. Brion, J. H. Schwartz, H. M. Lachman, B. J. Zavilowitz and G. J. Schwartz
Department of Pediatrics, Albert Einstein College of Medicine, Bronx, New York 10461.

The purpose of these studies was to characterize the development of H+ secretion by cultured inner medullary collecting duct (IMCD) cells. Differentiated IMCD cells derived from rat papillae develop in culture N-ethylmaleimide (NEM)- and dicyclohexylcarbodiimide (DCCD)-sensitive Na+-independent H+ pump, but showed substantial heterogeneity. Cells with pHi greater than or equal to 7.1, measured by 2',7'-biscarboxyethyl-5(6)-carboxyfluorescein (BCECF), showed more H+ pumping than did those with pHi less than 7.1. Quiescent cells in domes and in the center of growing nests often showed active H+ pumping activity, but rarely exhibited Na+-H+ exchange, whereas dividing cells at the periphery of the nests showed only Na+-H+ exchange. Differentiated IMCD cells also showed Na+-independent 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid (DIDS)-sensitive Cl(-)-HCO3- exchange that functioned best when pHi was greater than or equal to 7.1, and homogenates of IMCD cells expressed carbonic anhydrase (CA) activity and CA II mRNA. A subgroup of IMCD cells avidly bound fluorescent peanut agglutinin (PNA); this binding became more extensive with time in culture. The PNA-labeled cells showed increased BCECF uptake, higher pHi, and more H+ pumping activity than did cells not binding PNA. They could be isolated by gel-immobilized PNA and in culture showed more CA activity and H+ pumping activity than unselected monolayers. The percentage of cells binding PNA correlated well with CA activity, indicating that this subgroup is better specialized to secrete H+. The appearance of PNA binding sites and the development of high CA activity may be characteristic of IMCD cell differentiation in culture.

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