Application of scanning electron microscopy to x-ray analysis of frozen-hydrated sections. III. Elemental content of cells in the rat renal papillary tip.

Abstract

The electrolyte and water content of cellular and interstitial compartments in the renal papilla of the rat was determined by x-ray microanalysis of frozen-hydrated tissue sections . Papillae from rats on ad libitum water were rapidly frozen in a slush of Freon 12, and sectioned in a cryomicrotome at -30 to -40°C . Frozen 0.5-,um sections were mounted on carbon-coated nylon film over a Be grid, transferred cold to the scanning microscope, and maintained at -175°C during analysis . The scanning transmission mode was used for imaging. Structural preservation was of good quality and allowed identification of tissue compartments . Tissue mass (solutes + water) was determined by continuum radiation from regions of interest . After drying in the SEM, elemental composition of morphologically defined compartments (solutes) was determined by analysis of specific x-rays, and total dry mass by continuum. Na, K, CI, and H2O contents in collecting-duct cells (CDC), papillary epithelial cells (PEC), and interstitial cells (IC) and space were measured . Cells had lower water content (mean 58 .7%) than interstitium (77.5%) . Intracellular K concentrations (millimoles per kilogram wet weight) were unremarkable (79-156 mm/kg wet weight) ; P was markedly higher in cells than in interstitium . S was the same in all compartments . Intracellular Na levels were extremely high (CDC, 344 ± 127 SD mm/kg wet weight ; PEC, 287 ± 105; IC, 898 ± 194) . Mean interstitial Na was 590 ± 119 mm/Kg wet weight . CI values paralleled those for Na . If this Na is unbound, then these data suggest that renal papillary interstitial cells adapt to their hyperosmotic environment by a Na-uptake process.Cells of the rat renal papilla are exposed to wide changes in the ionic and osmotic composition of their environment . The papillary epithelium of the rat is exposed to urine whose osmolality ranges from <100 to >3,000 mosmol/kg H2O. Tubular and interstitial cells within the papilla live in the hypertonic environment associated with the urine-concentrating mechanism. Because few mammalian cell types are exposed to such environmental conditions, the mechanism by which these cells adapt to the high salt and urea content of their environment is of great interest to cell biologists. and Morgan (20), using in vitro centrifugation or incubation techniques, have reported that the Na content of papillary cells increases with increasing osmolality and reaches more than 400 mM. However, until recently no method existed for the 274 definition of chemical composition of defined cell types within the papilla. The development of techniques for direct x-ray microanalysis of frozen-hydrated tissue sections (19,22,23) now makes such analysis possible. MATERIALS AND METHODSSix male Long-Evans rats (bred in our colony), weighing 125-200 g, were housed individually in metabolic cages for 2 dor more before the experiment . They were given Purina Rat Chow (0.29% Na, 0.46% K; Ralston Purina Co., St. Louis, Mo.) and water ad libitum. An overnight urine sample was collecte...

Renal countercurrent system: Role of collecting duct convergence and pelvic urea predicted from a mathematical model

“…These data indicate that the computed value is within the range of the measured data. It should be mentioned that the data of Bulger et al (1981) have been confirmed, in general, by Beck et al (1981) who report some 450 mMol/1 of salt at the papillary level.…”

“…4.1) rises from 140 to 635 mMol/1 in the outer medulla and further to 894 in the papilla. Recent direct measurements of interstitial elemental concentrations by Bulger et al (1981) show the following values (wet weight, mMol/kg) at the papillary tip: Na 590 ± 119; CI 445 ± 115; K 42 ± 8. These data indicate that the computed value is within the range of the measured data.…”

A hyperpolarization-activated, cyclic nucleotide-gated, (Ih-like) cationic current and HCN gene expression in renal inner medullary collecting duct cells

“…IMCD basolateral membrane is immersed in a hyperosmotic interstitial fluid with a high Na ϩ , Cl Ϫ , K ϩ , and urea concentration (5,9,18,22,24). When the kidney acutely passes from a chronic diuresis state to an antidiuresis state, the inner medullary interstitial solute concentration is slowly raised (6,18,47).…”

Quantitative x-ray microanalysis of the elemental composition of individual myocytes in hypoxic rabbit myocardium.

“…Diffusible elements were preserved by means of suitable methods of LABORATORY INVESTIGATION-MYOCARDIAL METABOLISM tissue freezing and cryosectioning.3' 36 Electron probe x-ray microanalysis has been applied previously to study physiologic phenomena and cell damage in smooth, skeletal, and cardiac muscle and other tissues. [37][38][39][40][41][42][43][44][45][46][47][48][49][50][51][52][53][54][55][56] In this study, diffusible elements in myocytes of control and hypoxic myocardium were quantified by means of separately analyzed cryosections of fresh frozen tissues and gelatin-glycerol elemental standards. 32, 36 The specific hypotheses tested in this study were (1) that individual myocytes may exhibit important variation in the severity of alterations in intracellular ionic homeostasis in response to hypoxia and (2) that hypoxic myocytes may accumulate certain elements in quantities sufficient to impair organellar function and structure.…”