A unique affinity and adaptation of renomedullary interstitial cells for hypertonic medium

Collagenase-dispersed cells of renal papillary tissue from adult mongrel dogs were directly inoculated in a modified M.E.M. (Eagle's) giving an osmolality of approximately 1,000 mOsm/L by addition of urea and sodium chloride, and were cultured in an atmosphere of 95% air-5%CO2 at 37 degrees C. Within twelve hours after inoculation, spindle-shaped cells attached firmly to the surface of culture dishes, while the other cellular components of the inner medulla remained floating in the medium. After several days in culture, the colonies grew to form a confluent cell layer, which was composed of almost homogenous cells giving spindle-shape. These cells kept on the major characteristics of renomedullary interstitial cell (RIC) in morphology as well as in function to produce prostaglandin E. These results appear to be principally attributable to the unique characteristics of RIC, one of which is affinity for high osmolality and the other is different behavior in attachment to the dish. As the procedure proposed here was relatively simple and did not require a long period up to the development of monolayer, it would provide a promising model "in vitro" to study the humoral regulation of prostaglandin production.

The influence of chloride ions on renal outer medullary cell volume

1. Slices of rat renal outer medulla have been incubated in media made hyperosmotic (540 and 1055 m-osmole/kg H2O) by the addition of urea, and containing variable concentrations of Cl (90, 144, 189 and 215 mM) and constant concentrations of Na (180 mM) and K (5.9 mM). A small number of incubations have been conducted in the presence of 100 mM-Na. 2. Changes in cell volume during incubation have been calculated on the basis of initial and final slice weight and inulin space. 3. The capacity of cells to shrink in response to extracellular osmotic stress was related principally to the external Cl concentration rather than to osmolality, increases in concentration being associated with enhanced shrinkage. Shrinkage was accompanied by net loss of cellular Cl. The ratio between intra- and extracellular Cl concentration (ca. 0.41) remained constant in all media. 4. In media containing low Cl concentration (90 mM), reduction of media Na concentration to 100 mM enhanced shrinkage. This effect was not observed when medium Cl concentration was greater than 90 mM. 5. Ethacrynic acid-cysteine (1 mM) significantly impaired the shrinkage response to extracellular osmotic stress, and caused cell swelling in media of relatively low Cl concentration and osmolality. It did not abolish the dependency of cell volume upon Cl concentration. There was marked reduction in the net amount of Cl lost from cells. 6. Ethacrynic acid-cysteine caused an increase in cellular Na content only in media containing 540 m-osmole/kg H2O and Cl concentrations less than 215 mM. 7. Ouabain (1 mM) inhibited cell shrinkage to a lesser extent than ethacrynic acid-cysteine in all media except that causing the greatest shrinkage under control conditions (215 mM-Cl/1055 m-osmole/kg H2O). It is suggested that a ouabain-sensitive process may play an increasingly important role in Cl-related cell shrinkage as this becomes more pronounced. 8. The findings are consistent with the view that Cl ions influence cell volume both through their effective external osmotic pressure and by means of Cl-specific process; the latter is associated with net loss of cellular Cl. A dependence of this loss upon Na/k exchange-linked metabolism is inferred, but the present findings do not permit the active or passive nature of the extrusion to be defined.

Volume changes in cells of the outer medulla during perfusion of the rat kidney

1. A method is described for the perfusion of the rat kidney with a medium resembling rat plasma in its ionic constituents but with 3% polyvinylpyrrolidone (mol.wt. 44,000) replacing the plasma proteins. 2. In the early stages of perfusion, there was rapid swelling of the tubular cells in the outer medulla, a low glomerular filtration rate and a low filtration fraction. 3. After 30 min perfusion, the tubular cell volume in the outer medulla was normal and filtration had increased and stabilised. 4. Cell swelling and the low initial filtration fraction were prevented by (a) adding 50 mM-mannitol to the basic medium, (b) replacing 50 mM-NaCl with 50 mM-choline chloride, or (c) adding 5% human serum to the basic medium. 5. The addition of human serum to the perfusion medium depressed the fractional reabsorption of sodium and potassium; sodium from 0.94 +/- 0.01 (S.E. of mean) with the basic medium to 0.79 +/- 0.02 with basic medium +5% serum after 35 min perfusion; and potassium from 0.73 +/- 0.04 with the basic medium to 0.37 +/- 0.05 with the basic medium +5% serum after 35 min perfusion. 6. Two conclusions are drawn from the observations: first, that at the start of perfusion the effective internal osmolality of tubular cells of the outer medulla is greater than that of cortical cells and of the basic medium; and second, that the presence of small amounts of plasma proteins in the perfusion medium has a marked effect on the properties of plasma cell membranes.

Cyclic 3',5'-nucleotide phosphodiesterase; cytochemical localization in rat renomedullary interstitial cells

The localization of cyclic 3', 5' -nucleotide phosphodiesterase activity in rat renal papillae was examined by utilizing cytochemical methods. Renal medullary interstitial cells had predictable phosphodiesterase activity predominantly on the cytoplasmic border of dilated cisternal membranes. Cells of the collecting tubule and loop of Henle contained diffuse reaction product. Capillaries had reaction product localized in pinocytic vesicles. Addition of theophylline resulted in no deposition of reaction product in interstitial cells and in cells of the collecting tubule and loop of Henle, suggesting an inhibition of phosphodiesterase activity. Since the membranes of dilated cisternae of renal medullary interstitial cells have been shown to be related to prostaglandin synthesis and probably to the anti-hypertensive function of these cells, the finding of phosphodiesterase activity on these membranes suggests a possible role of cyclic AMP in these two functions.

Ouabain binding to renal tubules of the rabbit

It is well known that ouabain, a specific inhibitor of Na-K ATPase-dependent transport, interferes with renal tubular salt reabsorption. In this study, we employed radiochemical methods to measure the kinetics of [3H]ouabain binding to slices of rabbit renal medulla and high resolution quantitative autoradiography to determine the location and number of cellular binding sites. The kinetics obeyed a simple bimolecular reaction with an association constant of 2.86 +/- 0.63 SD x 10(3) M-1 min-1 and a dissociation constant of 1.46 x 10(-3) min-1, yielding an equilibrium binding constant of 0.51 x 10(-6) M. Binding was highly dependent upon temperature. At a concentration of 10(-6) M, the rate of accumulation between 25 degrees C and 35 degrees C exhibited a Q10 of 1.8. At 0 degree C the rate of ouabain dissociation was negligible. The specificity of binding was demonstrated with increasing potassium concentrations. At a concentration of 1 microM, 6 mM, and 50 mM K+ produced a 2.5- and 7-fold decrease, respectively, in the rate of ouabain accumulation observed at zero K+. Binding was completely inhibited by 1 mM strophanthin K. The major site of ouabain binding was the thick ascending limb; little or no binding was observed in thin limbs and collecting ducts. Moreover, binding was confined to the basolateral membranes. From autoradiographic grain density measurements, it was estimated that each cell contains over 4 x 10(6) ouabain binding sites or Na-K ATPase molecules. These results taken together with physiological and biochemical observations suggest that Na-K ATPase plays a key role in salt reabsorption by this segment.

Renal medulla: an endocrine organ involved in blood pressure regulation

The renal medulla is not often considered an endocrine organ, but recent evidence suggests that this part of the kidney may have important antihypertensive, endocrine functions. The antihypertensive factor(s) of the medulla have been localized to the interstitial cells and characterized as neutral and acidic lipids. The acidic lipids, or protstaglandins, have been the more extensively investigated. Animal and human studies indicate that prostaglandins may influence systemic arterial pressure directly or indirectly by promoting excretion of salt and water. Recent evidence suggests that prostaglandins may be mediators of the renin-angiotensin-aldosterone system, thus influencing blood pressure via this system that plays such a key role in blood pressure control.

Demonstration of prostaglandin synthesis in collecting duct cells and other cell types of the rabbit renal medulla

The renal medulla has a high capacity for prostaglandin production and the interstitial cells, which contain abundant lipid inclusions have been suggested to be the site of synthesis. However, histochemical studies have indicated that the collecting ducts are the main site of production. The object of the present study was to study the distribution of prostaglandin synthetase in the rabbit renal medulla by direct, quantitative determination of the enzyme activity in different cellular fractions. Slices were cut from rabbit renal papilla and immersed in a hypertonic saline solution. 92% of the collecting duct cells were then removed from the slices by suction through a micropipette. The remaining dissected slices thus contained mainly three cell types, cells of Henle's loop, endothelial cells, and interstitial cells. The isolated collecting duct fraction, the corresponding dissected slices, from which the colelcting duct cells were removed, as well as intact slices were assayed for prostaglandin synthetase activity using a quantitative assay with [14C] arachidonate as substrate. Of the prostaglandin in synthetase activity 39% was found in the collecting ducts, 53% in the dissected slices, and 7% in the dissection medium. It is thus concluded that significant prostaglandin synthetase activity is present in collecting duct cells as well as in at least one other cell type of the medulla.

Prostaglandin biosynthesis by rabbit renomedullary interstitial cells in tissue culture. Stimulation by angiotensin II, bradykinin, and arginine vasopressin

Rabbit renomedullary interstitial cells were isolated and grown in tissue culture. These cells synthesize 0.8 ng of prostaglandin E2 (PGE2) per microgram cellular protein per hour in monolayer tissue culture; prostaglandins A2 and F2alpha (PGA2 and PGF2alpha) biosynthesis was 10 and 5% of PGE2 biosynthesis, respectively. Arachidonic acid markedly stimulated the production of PGE2 and PGF2alpha, with conversion rates of 0.24 and 0.02%/h, respectively. Angiotensin II, hyperosmolality, bradykinin, and arginine vasopressin each stimulated PGE2 biosynthesis; maximum stimulation was 20, 3.7, 3.6, and 3.2 times basal production, respectively. PGE2 biosynthesis by the renomedullary interstitial cells was inhibited by isoproterenol, potassium, nonsteroidal anti-inflammatory agents (indomethacin, naproxen, ibuprofen, suprofen, meclofenamate, and acetylsalicylic acid), mepacrine (a phospholipase inhibitor), hydrocortisone, and cortisone. The rabbit renomedullary interstitial cell in tissue culture is a model system for the study of hormonal regulation of PGE2 biosynthesis.

Differentiation of renal tubular epithelium in renal transplantation cytology

Increased numbers of renal tubular epithelial cells are present in the urinary sediments of renal transplant recipients during acute rejection. Few investigators have described characteristics of renal tubular epithelial cells in cytologic preparations. This study compiles morphologic characteristics of various tubular epithelial cells and determines the type of the tubular cells present during acute allograft rejection. The results demonstrate that cuboidal forms from the small collecting ducts are the predominent tubular epithelial cells exfoliated in voided urine during acute allograft rejection.

Renomedullary interstitial cells in the spontaneously hypertensive rat

Renomedullary interstitial cells (RIC) are known to synthesize and release prostaglandins which may play a significant role in the development or severity of hypertension. The medulla of the spontaneously hypertensive rat contains RIC which are morphologically very similar to those previously described in the normotensive rat. The granularity of the RIC, however, was increased in the spontaneously hypertensive rat compared to normotensive Wistars (9.6 +/- 2.34 versus 5.3 +/- 2.05 granules per cell, respectively, p less than 0.001) or treated spontaneously hypertensive rats (7.2 +/- 1.65 granules per cell, p less than 0.001). Granule counts also increased in the presence of mild and moderate degrees of renal arteriolar sclerosis, but decreased in long standing hypertension with more severe and extensive lesions involving both arteries and arterioles. These results are consistent with the hypothesis that the RIC respond to an elevation of blood pressure in the spontaneously hypertensive rats by increased release of antihypertensive substances. In addition, the decrease in granularity of the RIC in the presence of extensive renal arteriolar and arterial damage suggests reduced ability to compensate for the elevated blood pressure and thus may contribute to the acceleration of hypertension.

[Characteristics of the energy metabolism in the kidneys in analgesic nephropathy]

Effect of prolonged treatment with acetyl salicylic acid (100 mg/kg) on energy metabolism was studied in dog kidney. Functional conditions of kidney were altered, which was manifested by an increase in excretion of sodium and by impairement is osmotic concentrating of urine. Studies of energy metabolism revealed uncoupling of oxidation and phosphorylation and also some decrease in the activity of glycolytic processes. The observed alterations in bioenergetics of kidney tissue are considered as important factors in development of analgetic nephropathy.