Effects of potassium-free media and ouabain on epithelial cell composition in toad urinary bladder studied with X-ray microanalysis

Abstract

The technique of X-ray microanalysis was used to study the composition of toad urinary bladder epithelial cells incubated in Na Ringer's and K-free medium, with and without ouabain. Following incubation under short-circuit conditions, portions of tissue were coated with an external albumin standard and plunge-frozen. Cryosections were freeze-dried and analyzed. In Na Ringer's, granular and basal cells, and also the basal portion of the goblet cells, had similar water and ion compositions. In contrast, mitochondria-rich cells contained less Cl and Na. On average, the granular cells and a subpopulation of the basal cells lost K and gained Na after ouabain and in K-free medium alone. However, there was considerable variation from cell to cell in the responses, indicating differences between cells in the availabilities of ion pathways, either as a consequence of differences in the numbers of such pathways or in their control. In contrast, the compositions of both the low Cl, mitochondria-rich cells and a sub-population of the basal cells were little affected by the different incubation conditions. This is consistent with a comparatively low Na permeability of these cells. The results also indicate that (i) much, if not all, of the K in the dominant cell type, the granular cells, is potentially exchangeable with serosal medium Na, and (ii) Na is accumulated from the serosal medium under K-free conditions. They also provide information about the role of the (Na-K)-ATPase in the maintenance of cellular K in K-free medium, being consistent with other evidence that removal of serosal medium K inhibits transepithelial Na transport by decreasing Na entry to the cells from the mucosal medium, rather than solely by inhibiting the basolateral membrane (Na-K)-ATPase.

Electron microprobe analysis of ouabain-exposed ciliary epithelium: PE-NPE cell couplets form the functional units

“…The methods used in this study for tissue freezing, cryosectioning, and analysis have been described in detail elsewhere (3,24).…”

Electron microprobe analysis of rabbit ciliary epithelium indicates enhanced secretion posteriorly and enhanced absorption anteriorly

“…The methods used in this study for tissue freezing, cryosectioning, and analysis have been described in detail elsewhere (3,31,33).…”

“…However, the sum of the normalized contents of Na and K [(Na ϩ K)/P] is a useful index of intracellular water content (1). Likewise, we have used the normalized anion gap, defined as (Na ϩ K Ϫ Cl)/P, as an approximate index of changes in intracellular HCO 3 Ϫ content (34), although other unmeasured anions can also contribute to this parameter. NPE, nonpigmented ciliary epithelial cells; PE, pigmented ciliary epithelial cells.…”

Villus and Crypt Cell Composition in the Secreting Mouse Jejunum Measured with X-ray Microanalysis

“…In the jejunum the epithelial cells are derived from a mitotically active region near the base of the crypt and migrate towards the villus tip where they are shed 2-3 days later (Gordon, 1989). In general, associated with senescence of epithelial cells is a marked increase in Na and Cl content and fall in K content, (Bowler et al, 1991;Rick et al, 1978). We identified a small number of cells in the albumin standard applied to the tissues before freezing.…”

“…To obtain measurements of cellular ion concentration spectra were collected from at least two relatively large areas of albumin above the cells. Data from these areas were then pooled to provide an average value and cellular composition (in mmol/kg wet weight) obtained by normalizing spectra to the known concentrations in the peripheral albumin standard (Bowler, Purves & Macknight, 1991;Rick, Dorge & Thurau, 1982). To obtain estimates of ion content spectra were obtained from an area confined to the nucleus and all values normalized to the phosphorous signal (Bowler et al, 1996).…”