Renal anatomy of the manatee, Trichechus manatus, Linnaeus

The manatee kidney is composed of several closely apposed lobes. These are formed by cortical folds (plicae corticales) that completely isolate the medullae, except where the medullae of adjacent lobes are partially fused. The cortex is continuous; its folds usually are separated, but only partially, by interlobar septa extending from the renal capsule. The cortex makes up approximately 57% of renal mass in adults and 68% in the calf. There are about 3 million glomeruli per kidney. The average is somewhat less than that expected of an adult eutherian of equal mass. The glomeruli, however, are large; they form 7.38% +/- 1.33 of cortical mass, which is above that for at least ten unrelated adult eutherians. The number of glomeruli per gram of cortex is considerably greater in the calf than in the adult. The medullae are about 43% of renal mass. The cortico-medullary thickness ratio is 0.08 to 0.24. All terminal collecting ducts open at a crater (cratera cribrosa) of varying depth. Hair-pin loops occur at all levels of medulla, and apparently all loops bend at their thick segment. Cortical loops occur in the medullary rays. Vascular bundles were evident at the cortico-medullary border and thin tubules extended into the medulla from the central ends of the medullary rays (cortical) in seven out of the nine kidneys. The renal pelvis is separated from the central ends of the cortical folds by delicate fascia through which pass the interlobar vessels. There are no fornices and no infundibula. The collagenous tissue of the pelvic wall extends across most of the pelvic surface of the outer medulla.

Immunocytochemical localization of Na+ channels in rat kidney medulla

Amiloride-sensitive Na+ channels were localized in semithin frozen sections of rat renal medullary collecting ducts, using polyclonal antibodies directed against purified bovine kidney Na+ channel protein. The apical plasma membrane of collecting duct principal cells was heavily stained by indirect immunofluorescence, whereas intercalated cells were negative. Basolateral plasma membranes of both cell types were unstained, as were subapical vesicles in the cytoplasm of these cells. In the thick ascending limb of Henle, some scattered granular fluorescence was seen in the cytoplasm and close to the apical pole of epithelial cells, suggesting the presence of antigenic sites associated with some membrane domains in these cells. No staining was detected in thin limbs of Henle, or in proximal tubules in the outer medulla. These results show that amiloride-sensitive sodium channels are located predominantly on the apical plasma membrane of medullary collecting duct principal cells, the cells that are involved in Na+ homeostasis in this region of the kidney.

Morphologic heterogeneity along the rat inner medullary collecting duct

The qualitative and quantitative morphologic features of the cells lining the inner medullary collecting duct (IMCD) in the outer (IMCD1), middle (IMCD2) and inner (IMCD3) segments were investigated. Kidneys of male rats were fixed by in vivo vascular perfusion with glutaraldehyde and processed for light microscopy and scanning and transmission electron microscopy. The IMCD1 consisted of both principal cells and intercalated cells similar to those present in the outer medullary collecting duct. The principal cells were covered with small microvilli and a single cilium. Most of the IMCD2 and the entire IMCD3 contained one cell type (IMCD cell). When compared with the principal cells, the IMCD cells were taller, had fewer basal infoldings and a lighter staining cytoplasm containing numerous free ribosomes and small electron-dense cytoplasmic bodies in the basal region. The luminal surface was covered with prominent microvilli, but had no cilia. Morphometric analysis demonstrated that the surface density of apical and basal plasma membranes decreased from IMCD1 to IMCD3. However, because of an overall increase in tubule volume from IMCD1 to IMCD3, there were no significant differences in the absolute area of apical or basal membranes between the three segments. In contrast, the absolute area of lateral membranes increased significantly from IMCD1 to IMCD3. This study demonstrates that the IMCD1 consists of principal cells and intercalated cells similar to those in the outer medullary collecting duct, whereas the cells in most of the IMCD2 and the entire IMCD3 appear to represent a distinct and separate cell type which we choose to call the IMCD cell. Thus, both morphologic and functional heterogeneity appear to exist along the IMCD.

Measurement of element content in isolated papillary collecting duct cells by electron probe microanalysis

A method was developed to measure the element content of freshly isolated papillary collecting duct (PCD) cells by electron probe microanalysis in a scanning electron microscope. After isolation, the cells were transferred onto a Thermanox support by centrifugation and the extracellular medium was removed by brief exposure to buffered ammonium acetate; cryofixation, freeze-drying, and coating with carbon followed. Under visual control in the scanning electron microscope the Na, Cl, K and P content of cell clusters (about 30 cells/cluster) was then measured by X-ray microanalysis. Cells incubated in control medium showed potassium:sodium ratios identical to those determined previously in cryosections of the same cells. In ouabain-treated cells sodium influx and potassium efflux was demonstrated. Potassium left the cells with a t1/2 of 21.7 min. The t1/2 of Na influx was 12.6 min for the first 15 min of incubation, whereafter further influx was markedly slower. Ouabain-induced sodium influx was inhibited 40% by amiloride. These results indicate that X-ray microanalysis can be applied to analyze the ion content of isolated cell clusters derived from the papillary collecting duct. Using ouabain and amiloride as inhibitors the suitability of the method to identify transport systems is demonstrated.

An inwardly-directed sodium-amino acid cotransporter influences steady-state cell volume in slices of rat renal papilla incubated in hyperosmotic media

The effect of a neutral amino acid, 2-aminoisobutyric acid (AIB) on steady state cell volume has been examined in rat renal papillary slices incubated in hyperosmotic media (2,000 mosmol/kg H2O) containing high concentrations of NaCl and urea (thus imitating papillary interstitial fluid in the intact kidney during antidiuresis). Volumes were significantly increased (P less than 0.001) when external AIB was raised from 0.1 to 10 mmol/l. Na+-dependent AIB uptake occurred, and there were net increases in cell contents of Na+ and Cl-. Replacement of Na+ by Li+, but not by other cations, did not influence the effect of AIB concentration on cell volume, but this was abolished when Cl- was replaced by other anions. The effect of AIB was abolished by diphenylamine-2-carboxylate (10(-3) mmol/l), bumetanide (at 1 mmol/l but not 10(-2) mmol/l) and by N,N'-dicyclohexylcarbodiimide (0.5 mmol/l), but not by amiloride (1 mmol/l) or 4-acetamido-4'-iso-thiocyanato-stilbene-2,2'-disulphonic acid (1 mmol/l), and was enhanced by the presence of Ba2+ or quinine (1 mmol/l). The findings are interpreted in terms of an inwardly-directed Na+-amino acid cotransporter, which determines steady-state volume, requires simultaneous entry of Cl- through conductive pathways, and whose effects on cell volume are moderated by K+ efflux through volume-sensitive K+ channels.

Sugar transport in isolated rat kidney papillary collecting duct cells

D-Glucose is an important substrate of energy metabolism and osmolyte synthesis in the renal papillary collecting duct. In order to characterize the cellular entry of D-glucose in this tubular segment, collecting duct cells were isolated from rat kidney papilla and the rate of D-glucose uptake was measured indirectly by monitoring the D-glucose-dependent O2 uptake in the presence of the uncoupler CCCP. D-Glucose uptake was found to be sodium-independent and not sensitive to phlorizin even at a concentration of 10(-3) M. Uptake was, however, completely inhibited by 10(-5) M cytochalasin B and 10(-4) M phloretin. The apparent Ki for cytochalasin B was 1.5 x 10(-6) M and for phloretin 2.0 x 10(-5) M. Studies on the substrate specificity revealed that at 1 mM D-mannose is taken up and metabolized to the same extent as D-glucose. A 50-fold higher concentration of 2-deoxy-D-glucose and 2-amino-2-deoxy-D-glucose inhibited D-glucose uptake completely whereas alpha-methyl-D-glucoside, D-allose, and D-galactose were without effect. Under conditions where D-glucose utilization was maximally stimulated an apparent Km of 1.2 mM and a Vmax of 1 mmol D-glucose/g protein.hour was found for D-glucose uptake. These results indicate that the D-glucose uptake into papillary collecting duct cells is probably mediated by a transport system similar to the one found in basal-lateral membranes of polarized renal, intestinal, and liver cells as well as in nonpolarized fat cells and erythrocytes.

Immunodissection of cortical and medullary thick ascending limb cells from rabbit kidney

A procedure was developed for isolating thick ascending limb cells from either the outer medulla or the inner cortex from rabbit kidneys. Dispersed cells derived from the medulla or cortex were incubated with goat anti-human uromucoid (Tamm-Horsfall glycoprotein) serum, washed, and applied to culture dishes coated with affinity-purified anti-goat immunoglobulin G. Nonadherent cells were removed by washing. Routinely, 10(6) or 7 X 10(4) adherent cells were obtained per gram of rabbit outer medulla or inner cortex, respectively. Greater than 97% of the adherent cells stained for Tamm-Horsfall antigen, and examination of freshly isolated cells by transmission electron microscopy established that they had morphological properties expected for thick limb cells. Freshly isolated medullary thick limb (MTALH) cells consistently accumulated cAMP in response to arginine vasopressin (AVP), thyrocalcitonin, prostaglandin E2 (PGE2), and glucagon. PGE2, thyrocalcitonin, parathyroid hormone, and AVP, but not isoproterenol or glucagon, reproducibly stimulated cAMP accumulation in freshly isolated cortical thick limb (CTALH) cells. MTALH cells produced immunoreactive PGE2 when incubated with 10 microM arachidonic acid. In summary, large numbers of highly purified and hormonally responsive rabbit MTALH and CTALH cells can be obtained by immunodissection using commercially available antibody preparations. Because the Tamm-Horsfall antigen is present as an extracellular determinant on thick ascending limb epithelia from many species, this general approach likely can be used to isolate CTALH and MTALH cells from most mammalian kidneys.

Atrial natriuretic peptides inhibit conductive sodium uptake by rabbit inner medullary collecting duct cells

The inner medullary collecting duct (IMCD) effects net sodium reabsorption under the control of volume regulatory hormones, including atrial natriuretic peptides (ANP). These studies examined the mechanisms of sodium transport and its regulation by ANP in fresh suspensions of IMCD cells. Sodium uptake was inhibited by amiloride but insensitive to furosemide, bu-metanide, and hydrochlorthiazide. These results are consistent with uptake mediated by a sodium channel or Na+/H+ exchange. To determine the role of sodium channels, cells were hyperpolarized by preincubation in high potassium medium followed by dilution into potassium-free medium. Membrane potential measurements using the cyanine dye, Di(S)-C3-5 verified a striking hyperpolarization of IMCD cells using this protocol. Hyperpolarization increased the apparent initial rate of sodium uptake fourfold. Amiloride and ANP inhibited potential-stimulated sodium uptake 73% and 65%, respectively; the two agents together were not additive. Addition of 5 mM sodium to hyperpolarized cells resulted in a significant amiloride-sensitive depolarization. Half-maximal inhibition of potential-driven sodium uptake occurred at 3 X 10(-7) M amiloride, and 5 X 10(-11) M ANP. We conclude that sodium enters IMCD cells via a conductive, amiloride-sensitive sodium channel, which is regulated by ANP. ANP inhibition of luminal sodium entry in the IMCD appears to contribute to the marked natriuretic effect of this hormone in vivo.

Immunodissection of mitochondria-rich cells from rabbit outer medullary collecting tubule

Two types of mitochondria-rich (MR) cells have been identified in the rabbit collecting tubule based on differences in immuno- and lectin cytochemistry. We have produced a monoclonal antibody, immunoglobulin (Ig) G1 (mr-mct), that reacts specifically with the MR cells (identified by positive histochemical staining for succinate dehydrogenase) found predominantly in the outer medulla (OM) and cells of the proximal tubule. IgG1 (mr-mct) reacted with 18 +/- 2% of the cells of the outer medullary collecting tubule (OMCT) and did not colocalize with peanut lectin-binding MR cells in the cortex. To isolate MR-OMCT cells, collecting tubule cells from collagenase dispersions of the OM were first adsorbed onto plates treated with a monoclonal antibody reactive against all of the OMCT cells. Of the isolated OMCT cells, 17% reacted with IgG1 (mr-mct). Cells were then detached from the plate and transferred to plates coated with IgG1. Greater than 70% of the adsorbed cells were MR as determined by positive staining with IgG1 (mr-mct). This enrichment of MR-OMCT cells was associated with a severalfold increase in adenosine 3',5' cyclic monophosphate (cAMP) production in response to isoproterenol and an attenuated increase in cAMP production to vasopressin. In summary, we report the isolation of highly enriched populations of MR cells from the OM using two-stage solid-phase immunoadsorption. This approach should provide a useful and convenient method for further investigations of the physiological role of these poorly understood tubular cells.

Cellular osmoregulation in renal medulla

Cells of the renal medulla adapt osmotically to varying external electrolyte concentrations mainly by changing the intracellular content of small organic osmoeffectors (osmolytes) such as sorbitol, inositol and trimethylamines. This implies that despite extreme variations in extracellular tonicity the intracellular concentrations of monovalent electrolytes are stabilized at levels optimal for enzyme function and cell metabolism. In contrast to inorganic electrolytes these organic osmolytes are metabolically neutral and thus do not affect cell metabolism. In addition, some of these organic osmoeffectors, the trimethylamine compounds, are known to counteract the deleterious effects of high urea concentrations (prevailing in antidiuresis) on structure and function of cell proteins.

Morphometric studies of the renomedullary interstitial cells

The renomedullary interstitial cell (RIC) is a unique cell found in the renal medullary interstitium among the collecting ducts, Henle's loop, and the vasa recta. A combination of morphologic and physiologic studies has defined some of the properties of this cell, which is the apparent source of the mediators of the antihypertensive function of the kidney. These may include prostaglandins (PGE2), APRL or platelet activating factor, and the incompletely defined neutral lipid, ANRL (or medullipin), the most likely candidate for this function. The lipid droplets in the RIC apparently are the precursors of the mediator(s). Degranulation of the RIC by an experimental maneuver usually indicates increased activity of these cells. The presence of abundant well-granulated RIC in a kidney indicates a resistance of that animal to the induction of salt-sensitive forms of experimental hypertension. There is definite evidence for an extrarenal antihypertensive function of the RIC mediators, but an intrarenal effect also is considered.

Experimental depletion of different renal interstitial cell populations

To define different populations of renal interstitial cells and investigate some aspects of their function, we studied the kidneys of normal rats and rats with hereditary diabetes insipidus (DI, Brattleboro) after experimental manipulations expected to alter the number of interstitial cells. DI rats showed an almost complete loss of interstitial cells in their renal papillae after treatment with a high dose of vasopressin. In spite of the lack of interstitial cells, the animals concentrated their urine to the same extent as vasopressin-treated normal rats, indicating that the renomedullary interstitial cells do not have an important function in concentrating the urine. The interstitial cells returned nearly to normal within 1 week off vasopressin treatment, suggesting a rapid turnover rate of these cells. To further distinguish different populations of interstitial cells, we studied the distribution of class II MHC antigen expression in the kidneys of normal and bone-marrow depleted Wistar rats. Normal rats had abundant class II antigen-positive interstitial cells in the renal cortex and outer medulla, but not in the inner medulla (papilla). Six days after 1000 rad whole body irradiation, the stainable cells were almost completely lost, but electron microscopic morphometry showed a virtually unchanged volume density of interstitial cells in the cortex and outer medulla, as well as the inner medulla. Thus, irradiation abolished the expression of the class II antigen but caused no significant depletion of interstitial cells.

Mitotic response to high protein intake in different renal cell types in weanling rats

We examined the effect of high protein intake on the mitotic response (3H-thymidine incorporation) in the glomerulus, proximal tubule (PT), thick ascending limb of Henle (TAL), distal tubule (DT) and collecting duct (CD) in kidneys from 16- to 24-day-old rats that received an isocaloric diet containing 21% (NP) and 50% (HP) protein from 16 days of age. Nephron filtration rate was also determined. After two days of HP diet, thymidine incorporation (TI) was significantly increased in PT and TAL. After two days on HP diet TI was most pronounced in TAL. After eight days on HP diet TI remained elevated in PT, but not in TAL. HP did not increase TI in DT or CD. The glomerular TI was the same in HP as in NP rats after two and four days on the diet, but was significantly elevated after eight days on HP diet. The nephron filtration rate was increased after two days and remained significantly elevated after eight days on HP diet. The proximal tubule fractional reabsorption was the same in 24-day-old NP and HP rats. We conclude that the results are compatible with the hypothesis that the Na load is a major factor triggering tubular growth after HP intake. Glomerular growth is secondary to increase in nephron filtration rate.

Solute transport and epithelial cell volume regulation

1. The regulation of epithelial cell volume is an essential requirement for normal tissue function and the maintenance of cellular integrity. 2. Renal papillary epithelial cells utilize an organic to compensate for the shrinkage associated with exposure to hypertonic solutions. 3. These cells synthesize the polyol, sorbitol, to increase their intracellular solute content. 4. Sorbitol is synthesized from glucose by the enzyme aldose reductase; exposure of the cells to hypertonic media causes aldose reductase synthesis and subsequent sorbitol generation over a two or three day period. 5. The intracellular signal for the formation of aldose reductase is not yet identified.

The volume and ionic composition of cells in incubated slices of rat renal cortex, medulla and papilla

The apparent extracellular space in incubated slices of rat renal cortex, medulla and papilla has been measured using three differently sized marker molecules, mannitol, sucrose and inulin. Cellular volumes have been estimated by following the efflux of 3-O-methyl-D-glucose from equilibrated slices. Sucrose appears to be the most accurate extracellular marker in each of the regions examined, in that the sum of its volume of distribution plus cellular volume approximates most closely to the total slice fluid volume. Inulin has the same volume of distribution as sucrose in cortical slices, but under-penetrates medullary and papillary tissue. Mannitol overestimates the extracellular space in all three regions, although its larger volume of distribution, relative to that of sucrose, was not statistically significant in papillary slices. When cell volume and composition are estimated (a) using sucrose as extracellular marker and (b) making appropriate allowance for the presence of bound tissue electrolytes, it is found that cells in each region have low Na+ and high K+ concentrations and contents. When papillary slices are incubated in medium of very high osmolality (NaCl plus urea, 2000 mosmol/kg H2O) there is a moderate (approx. 23%) decrease in cell volume and an increase in cell fluid Na+ and Cl- concentrations equal to approx. 50% of the increase in the extracellular concentrations. Cell K+ concentrations remain unchanged. The results show that cells in renal slices are able to maintain high K+-to-Na+ ratios when incubated in isosmotic (cortex) or moderately hyperosmotic media (medulla and papilla), and suggest that regulation of papillary cell volume following hyperosmotic shock can only partly be ascribed to uptake of extracellular electrolytes.

Biphasic effect of dexamethasone on urinary prostaglandins in rats: relation to alterations in renal medulla triglycerides and prostaglandin metabolism

This study was designed to characterize the time course of the effects of dexamethasone (2.5 mg kg-1 week-1, sc) on the renal arachidonate-prostaglandin (PG) system and to define the effect of the steroid on the interstitial cells of the renal inner medulla (RIC). The RIC are rich in triglycerides, which, due to their high content of arachidonic acid, may be a source of arachidonate for PG synthesis during conditions of phospholipase inhibition. After 1 day of dexamethasone treatment, the urinary excretion of PGE2 and PGF2 alpha was reduced to about 50% of the control value (P less than 0.05), and angiotensin II-induced release of arachidonic acid and PGs from renal medulla slices was blunted (P less than 0.05). In contrast, dexamethasone treatment did not affect ionophore A23187-induced release of PGs and arachidonic acid from renal medulla slices. By day 3 of dexamethasone treatment, urinary excretion of PGE2 and PGF2 alpha had returned to control levels, and by days 5 and 14 the excretion rates of both were clearly increased (P less than 0.05). The rise in urinary PG excretion was accompanied by a reduction of renal 15-hydroxyprostaglandin dehydrogenase activity, augmentation of renal medulla microsomal PG synthetase activity, and diminution of renal medulla triglycerides, the latter associated with a reduction in the number of RIC and of RIC osmiophilic granules. This study demonstrates that the effects of dexamethasone on urinary PG are biphasic; this may reflect the changing balance between the opposing actions of the steroid on renal PG-synthesizing and catabolizing enzymes and the inhibitory effect on the synthesis of renal PG that is linked to activation of specific renal lipases by endogenous factors such as angiotensin II.

Intercalated cells of the rat inner medullary collecting duct

There is increasing evidence of acidification along the entire mammalian collecting duct including the inner medullary collecting duct (IMCD). Recent studies have provided morphologic evidence that the intercalated cells are involved in hydrogen ion secretion in the cortical and outer medullary collecting duct of the rat. In the present study we performed a quantitative and qualitative morphologic examination of the intercalated cells in the IMCD of the rat and compared the results to observations obtained from intercalated cells in the collecting duct in the inner stripe of the outer medulla (OMCDi). Kidneys of male rats were preserved by in vivo perfusion with glutaraldehyde and processed for morphologic evaluation. With light microscopy and scanning electron microscopy intercalated cells were found in the outer third of the IMCD (IMCD1) and accounted for 10% of the total cell population. They were absent in the terminal two-thirds of the IMCD. Examination of the intercalated cells using transmission electron microscopy revealed striking similarities between the cells of the IMCD1 and those in the OMCDi. In addition, no differences were found in the surface densities of the apical or basolateral plasma membranes or the volume densities of the mitochondria of the intercalated cells in the two regions. In light of the morphologic similarity with the intercalated cells of the OMCDi that are believed to be involved in hydrogen ion secretion, it is likely that the intercalated cells of the IMCD1 are also involved in the acidification of tubular fluid.

Angiotensin converting enzyme predominates in the inner cortex and medulla of the rat kidney

Regional distribution of angiotensin converting enzyme(ACE) in the rat kidney was studied. The ACE activities in the inner cortex and outer medulla were about 10 and 5 times those in the outer cortex, respectively. The activity in the inner medulla or papilla was much the same as that in the outer cortex. Immunofluorescence was greatest in the proximal tubules in the inner cortex, while the outer medulla and the inner medulla or papilla showed a weak fluorescence. The brush border membranes isolated from the inner cortex also possessed about 10 times the ACE activity seen in the outer cortex. The results indicate that the major source of renal ACE is not the proximal convoluted tubules in the outer cortex, but rather the brush border membranes of proximal tubules in the inner cortex. The contribution of ACE in the inner cortex would therefore be predominant.

Transepithelial ammonia concentration gradients in inner medulla of the rat

Transport of NH3 from loops of Henle to medullary collecting ducts has been proposed to play an important role in renal ammonia excretion. To determine whether transepithelial ammonia concentration gradients capable of driving this transport are present in the inner medulla, micropuncture experiments were performed in control rats and in rats with chronic metabolic acidosis. In situ pH and total ammonia concentrations were measured to calculate NH3 concentrations ([NH3]) for base and tip collecting duct, loop of Henle, and vasa recta. In control and acidotic rats, [NH3] in the loop of Henle was significantly greater than [NH3] in the collecting ducts. [NH3] did not differ in loop of Henle and adjacent vasa recta in either group of rats, indicating that NH3 concentration gradients between loop and collecting duct represent NH3 gradients that are present between medullary interstitium and collecting duct. During acidosis, an increase in collecting duct ammonia secretion was associated with an increase in the NH3 concentration difference between loop of Henle and collecting duct but occurred in the absence of a fall in collecting duct pH. The NH3 concentration gradient favoring diffusion of NH3 into the collecting ducts increased during acidosis because [NH3] in the loop of Henle and medullary interstitium increased more than [NH3] in the collecting duct. These findings indicate that transport processes involved in medullary ammonia accumulation play an important role in regulating ammonia secretion into the inner medullary collecting duct in vivo and that a fall in inner medullary collecting duct pH is not necessarily required for ammonia secretion by this segment to increase during chronic metabolic acidosis.

Retention of differentiated characteristics by cultures of defined rabbit kidney epithelia

Rabbit nephron segments of proximal convoluted tubules (PCT); proximal straight tubules (PST); cortical and medullary thick ascending limbs of Henle's loop (CAL, MAL); and cortical, outer medullary, and inner medullary collecting tubules (CCT, OMCT, IMCT) were individually microdissected and grown in monolayer culture in hormone supplemented, defined media. Factors favoring a rapid onset of proliferation included young donor age, distal tubule origin, and the addition of 3% fetal calf serum to the medium. All primary cultures had polarized morphology with apical microvilli facing the medium and basement membrane-like material adjacent to the dish. Differentiated properties characteristic of the tubular epithelium of origin retained in cultures included ultrastructural characteristics and cytochemically demonstrable marker enzyme proportions. PCT and PST were rich in alkaline phosphatase; CAL stained strongly for NaK-ATPase; CCT contained two cell populations with regard to cytochrome oxidase reaction. A CCT-specific anti-keratin antibody (aLEA) was immunolocalized in CCT cultures, and a PST cytokeratin antibody stained PST cultures. The biochemical response of adenylate cyclase to putative stimulating agents was the same in primary cultures as in freshly isolated tubules. In PCT and PST adenylate cyclase activity was stimulated by parathyroid hormone (PTH) but not by arginine vasopressin (AVP); CAL and MAL adenylate cyclase was stimulated by neither PTH nor AVP; CCT, OMCT, and IMCT adenylate cyclase was stimulated by AVP but not by PTH. NaF stimulated adenylate cyclase activity in every cultured segment. It is concluded that primary cultures of individually microdissected rabbit PCT, PST, CAL, MAL, CCT, OMCT, and IMCT retain differentiated characteristics with regard to ultrastructure, marker enzymes, cytoskeletal proteins, and hormone response of adenylate cyclase and provide a new system for studying normal and abnormal functions of the heterogeneous tubular epithelia in the kidney.

An immuno-electron-microscopic study of the localization of VIP-like immunoreactivity in the adrenal gland of the rat

VIP-like immunoreactivity was revealed in a few chromaffin cells, medullary ganglion cells and a plexus of varicose nerve fibers in the superficial cortex and single varicose fibers in the juxtamedullary cortex and the medulla of the rat adrenal gland. VIP-like immunoreactive chromaffin cells were polygonal in shape without any distinct cytoplasmic processes and they appeared solitarily. Their cytoplasm contained abundant granular vesicles having a round core and the immunoreactive material was localized to the granular core. VIP-immunoreactive ganglion cells were multipolar and had large intracytoplasmic vacuoles. The immunoreactive material was localized not only in a few granular vesicles but also diffusely throughout the axoplasm. VIP-immunoreactive varicose nerve fibers in the superficial cortex were characterized by abundant small clear vesicles and some large granular vesicles, while those in the juxtamedullary cortex and medulla and the ganglionic processes were characterized by abundant large clear vesicles, as well as the same vesicular elements as contained in the nerves in the superficial cortex. The immunoreactive material was localized on the granular cores and diffusely in the axoplasm in both nerves. Based on the similarity and difference in the composition of the vesicles contained in individual nerves, it is likely that the VIP-immunoreactive nerve fibers in the medulla and the juxtamedullary cortex are derived from the medullary VIP-ganglion cells, while those in the superficial cortex are of extrinsic origin. The immunoreactive nerve fibers in both the cortex and the medulla were often in direct contact with cortical cells and chromaffin cells, where no membrane specializations were formed.(ABSTRACT TRUNCATED AT 250 WORDS)

Na-K-Cl cotransport in apical membrane of rabbit renal papillary surface epithelium

The renal papillary surface epithelium is exposed to pelvic urine on its apical surface and to inner medullary interstitium on its basolateral surface. To investigate transport in this epithelium, we dissected it free from the renal papilla of rabbits and mounted it in a chamber that allowed both sides to be bathed independently. Cell volume was measured at 25 degrees C utilizing computerized quantitative microscopy. Addition of ouabain (10(-4) M) to the basolateral solution induced a 20% volume increase. This volume increase was completely inhibited by the removal of apical bath NaCl, Na+, K+, or Cl- but not by the removal of urea. Bumetanide, down to 10(-9) M in the apical bath, completely inhibited the ouabain-induced swelling. Changes in apical bath osmolality, resulting from addition or removal of NaCl, caused cell volume changes that were greater than could be accounted for by osmotic water flow alone. This hyperresponse was blocked by bumetanide and was stimulated by vasopressin (10(-8) M). These observations are consistent with the presence of Na-K-ATPase in the basolateral membrane and a bumetanide-sensitive, vasopressin-responsive Na-K-Cl co-transporter in the apical membrane.

The (Na+, K+)ATPase of rat kidney: purification, biosynthesis, and processing

(Na+, K+)ATPase was purified from rat renal outer medulla by concanavalin A- and wheat germ agglutinin-lectin Sepharose affinity chromatographies. The antibody, which was raised in rabbits, markedly inhibited ATPase activity. The monospecificity of this antibody was assayed by the Ouchterlony double immunodiffusion and Western blotting tests. The endoplasmic reticulum (ER)-rich, and Golgi-rich subfractions were prepared from the rat kidney microsomal fraction by sucrose density gradient centrifugation. On the immunoblot, the molecular weight of the alpha subunit in both fractions was 95 kilodalton (Kd); whereas, that of the beta subunit was 50 Kd in the ER-rich fraction and 54 Kd in the Golgi-rich fraction. When treated with endoglucosidase H, the 50 Kd component was converted to 38 Kd, but the 54 Kd component was endoglucosidase H resistant. These results suggest that the beta subunit (38 Kd) is glycosylated cotranslationally in the ER (50 Kd) then is converted to the mature type subunit (54 Kd) in the Golgi apparatus.

Dynamic response of PG synthesis to peptide hormones and osmolality in renal tubular cells

A superfusion technique was adapted to collagenase-dispersed renal medullary and cortical tubular cells to study prostaglandin (PG) synthesis in response to arginine vasopressin (AVP), angiotensin II (ANG II), bradykinin (BK), Ca2+ ionophore A23187, and to changes in osmolality. Medullary and cortical cells promptly responded to the stimuli by an increase in PGE2 and PGF2 alpha production, whereas 6-keto-PGF1 alpha was not detected. AVP and BK were active on medullary cells, and ANG II was active mainly on cortical cells. A23187 stimulated PG synthesis in both cells but predominantly in the medulla. PG synthesis was dependent on the presence of extracellular Ca2+. The Ca2+ entry blocking agents verapamil and lanthanum did not inhibit the PG response to AVP, BK, and ANG II. Thus peptide hormone-stimulated PG synthesis in renal tubular cells did not depend on Ca2+ influx through channels blocked by these agents. Hyperosmolar NaCl or mannitol stimulated PG synthesis in cortical and, more markedly, in medullary cells. Hyperosmolar urea inhibited PGE2 synthesis stimulated by peptide hormones, NaCl, and A23187 in both cell preparations. In conclusion, the superfusion of isolated tubular cells is a useful method to study the dynamic aspects of renal PG release in response to various sequentially applied stimuli.

Intracellular pH regulation and proton transport by rabbit renal medullary collecting duct cells. Role of plasma membrane proton adenosine triphosphatase

Proton secretion in the renal medullary collecting duct is thought to occur via a luminal proton-ATPase. In order to determine what mechanism(s) participate in proton transport across medullary collecting duct (MCD) cells membranes, intracellular pH (pHi) regulation and proton extrusion rates were measured in freshly prepared suspensions of rabbit outer MCD cells. Cells were separated by protease digestion and purified by Ficoll gradient centrifugation. pHi was estimated fluorometrically using the entrapped intracytoplasmic pH indicator, 6-carboxyfluorescein. Proton extrusion rates were measured using a pH stat. The resting pHi of MCD cells was 7.19 +/- 0.05 (SE) in a nonbicarbonate medium of pH 7.30. When cells were acidified by exposure to acetate salts or by abrupt withdrawal of ammonium chloride, they exhibited pHi recovery to the resting pHi over a 5-min time-course. Depletion of greater than 95% of cellular ATP content by poisoning with KCN in the absence of glucose inhibited pHi recovery. ATP depletion inhibited proton extrusion from MCD cells. Treatment with N-ethylmaleimide also inhibited pHi recovery. In addition, cellular ATP content was dependent on transmembrane pH gradients, suggesting that proton extrusion stimulated ATP hydrolysis. Neither removal of extracellular sodium nor addition of amiloride inhibited pHi recovery. These results provide direct evidence that a plasma membrane proton-ATPase, but not a Na+/H+ exchanger, plays a role in proton transport and pHi regulation in rabbit MCD.

Laminin increases both levels and activity of tyrosine hydroxylase in calf adrenal chromaffin cells

We have investigated the effects of substrate-bound laminin on levels of enzymes of the catecholamine biosynthetic pathway in primary cultures of calf adrenal chromaffin cells. Laminin increases the levels of the enzymes tyrosine hydroxylase, dopamine-beta-hydroxylase, and phenylethanolamine-N-methyl-transferase. This effect is selective, in that levels of other enzymes (lactate dehydrogenase, aromatic amino acid decarboxylase, and acetylcholinesterase) are not increased. The effect of laminin can be blocked by antibodies directed against a fragment of the heparin-binding domain of the molecule, whereas antibodies directed against other fragments do not block the increase in tyrosine hydroxylase. Thus the laminin domain involved in enzyme regulation in chromaffin cells is apparently the same as that previously implicated in laminin's interactions with neurons to potentiate survival and stimulate neurite outgrowth (Edgar, D., R. Timpl, and H. Thoenen, 1984, EMBO (Eur. Mol. Biol. Organ.) J., 3:1463-1468). The increase in chromaffin cell tyrosine hydroxylase levels is preceded by an activation of the enzyme in which the Vmax (but not the Km) is altered. The effects of laminin appear to be developmentally regulated, since neither activation nor increased levels of tyrosine hydroxylase occur in adult adrenal chromaffin cells exposed to laminin.

Bradykinin-induced changes in phosphatidyl inositol turnover in cultured rabbit papillary collecting tubule cells

Rabbit renal papillary collecting tubule cells were isolated as a homogeneous population and grown in primary culture. These cells were maintained in fully defined medium to inhibit fibroblast overgrowth and to facilitate labeling of endogenous inositol phospholipids with myo-[2-3H]inositol with high specific activity. These cells demonstrated the morphology, cyclic AMP responsiveness, and prostaglandin E2 (PGE2) elaboration, consistent with previous published characterizations. When cells labeled with myo-[2-3H]inositol were stimulated by bradykinin at 10(-7) M, time-dependent and reversible changes in the distribution of inositol polyphosphates were observed. Inositol 1,4,5-triphosphate and inositol 1,4-diphosphate showed time-dependent and dose-dependent increases to maximal levels of 225 and 223% of control, respectively. These data indicate that the elaboration of inositol polyphosphates is a biochemical correlate to bradykinin stimulation and may play a role in PGE2 release in renal papillary collecting tubule cells.

Differentiated lines of cells from rabbit renal medullary thick ascending limbs grown on amnion

Previously we grew differentiated primary epithelial tissue cultures from rabbit renal medullary thick ascending limbs but were unable to subculture them into lines. Now, following the use of amnion as a support during the initial passages, two cell lines have grown from single fragments of medullary thick ascending limbs. Cells have now been in culture past 12 passages over more than 2 yr. On confluence they formed morphologically differentiated epithelial monolayers with polarization of the cells visible on electron microscopy. They had apical zonula occludens and microvilli, lateral cellular interdigitations, and basal membranes flat against the support. "Domes" often were visible when the epithelia formed on dishes, indicative of salt and water transport. Other functional differentiation in some passages of one line or the other included presence of Tamm-Horsfall protein (demonstrated by immunofluorescence) or transepithelial voltage oriented apical surface positive. Both the Tamm-Horsfall protein and the voltage are normally expressed by intact medullary thick ascending limbs and are characteristic of this particular nephron segment.

Transmembrane potential of renal papillary epithelial cells: effect of urea and DDAVP

To define how renal papillary epithelial cells respond to wide changes in the ionic and osmotic composition of their environment, measurements were made of the transmembrane potential differences (PD) of rat renal papillary epithelial cells in vitro in media containing 100 mM NaCl, 100 mM KCl, 1.5 mM CaCl2, and 1 mM MgSO4 plus varying amounts of urea and/or sucrose up to 1,400 mM. Glass microelectrodes (resistance 25-75 M Omega) were used. With added sucrose, no change in PD from the initial value of -9.3 +/- 1.3 (SD) mV (n = 29) (cell interior negative) was found. With added urea, alone or while osmolality was maintained nearly constant with sucrose, the PD changed in a triphasic manner, depolarizing to -5.3 mV at 50 mM urea, hyperpolarizing to -20.0 mV at 150 mM urea, and then depolarizing again to -5.5 mV at 1,400 mM urea. When bath potassium was decreased to 10 meQ/liter (choline replacement) the PD hyperpolarized to -46.9 +/- 5.0 (SD) mV (n = 32). DDAVP, a nonpressor vasopressin analogue, and 8-bromo-cAMP depolarized the membrane to -5 mV in the presence of urea but did not change PD when urea was absent. These observations suggest an interaction between urea and ionic movement or conductance in rat renal papillary epithelial cells.

The antihypertensive function of the kidney. Its elucidation by captopril plus unclipping

Unclipping the one-kidney, one-clip hypertensive rat during a free flow of urine caused the blood pressure to return to normal levels within about 3 hours. We found that administration of captopril plus unclipping caused the blood pressure to return to normal in minutes (17 +/- 4). Ureterocaval anastomosis plus captopril plus unclipping also caused the blood pressure to return to normal in minutes (8.8 +/- 2). Thus, the potentiation of the drop in blood pressure does not seem to be due to a volume effect. Administration of indomethacin and aprotinin did not prevent a rapid decline of the blood pressure after unclipping, but the decline was less rapid than that occurring after captopril and unclipping, which suggests that prostaglandin may have some effect on this mechanism. Saralasin administration did not potentiate the antihypertensive action of captopril plus unclipping. Chemical papillectomy prevented the drop in blood pressure after unclipping. The bolus dose of captopril to the hypertensive rat often caused a transient depressor effect resembling that due to the antihypertensive neutral renomedullary lipid, which suggests secretion of this lipid into the blood. The renomedullary interstitial cells accumulated large lipid granules after captopril administration. These cells also degranulated after unclipping. These findings are consistent with the hypothesis that the renal papilla secretes an antihypertensive hormone after unclipping. At present, antihypertensive neutral renomedullary lipid is the main putative hormone.

The morphology and antihypertensive effect of renomedullary interstitial cells derived from Dahl sensitive and resistant rats

The renomedullary interstitial cell (RIC) has been implicated in the antihypertensive action of the kidney. This cell has been isolated in tissue culture and shown to have an antihypertensive action in several models of experimental hypertension. Morphometric studies of RIC in vivo from Dahl rats sensitive and resistant to the hypertensive effects of high-salt diets indicate major differences between the RICs. These cells were therefore isolated from salt-sensitive and salt-resistant strains of rat, grown, and maintained in tissue culture. Major morphologic differences between the two cell lines were noted and persisted for multiple tissue culture passages. The cells from resistant animals were larger and had more lipid granules. These differences were similar to those seen in vivo. In short-term experiments these cells were compared for their antihypertensive effect. The two cell lines were injected subcutaneously into two groups of hypertensive recipient rats, one group of Dahl salt-sensitive rats on a high-salt diet and one group of Wistar rats subjected to the one-kidney, one-clip Goldblatt procedure. In both cases differences were noted between the cell lines. These data support the concept that differences between the Dahl salt-sensitive and salt-resistant rats may be related to variations in their RIC.

Chemically induced renal papillary necrosis and upper urothelial carcinoma. Part 1

In the past, renal papillary necrosis (RPN) has been commonly associated with long-term abusive analgesic intake, but over recent years a wide variety of industrially and therapeutically used chemicals have been shown to induce this lesion experimentally or in man. Destruction of the renal papilla may result in: (1) secondary degenerative cortical changes which precede chronic renal failure or (2) a rapidly metastasizing upper urothelial carcinoma, which has a very poor prognosis. This article will briefly review the published data on the morphology, function, and biochemistry of the normal renal medulla and the pathology associated with RPN, together with the secondary changes which give rise to cortical degeneration or epithelial carcinoma. It will then examine in detail those chemicals which have been reported to cause RPN in an attempt to delineate structure-activity relationships. Finally, the many different theories that have been proposed to explain the pathophysiology of RPN will be examined and an hypothesis will be put forward to explain the primary pathogenesis of the lesion and its secondary consequences.

Renotropic stimulation of DNA synthesis of proximal tubules and endothelial cells in the outer medulla

We explored the effects of ovine pituitary-derived renotropin on renal DNA synthesis in castrated hypophysectomized mice. Administration of the preparation at a dose of 47 micrograms for 5 days was followed by significant increases in renal DNA (134% of controls), and in kidney dry weight, protein and RNA. A time course study showed that [3H]-thymidine incorporation into renal DNA peaked at 8-10 h after one injection (60 micrograms) 1.9 times higher than in controls. Autoradiographic studies indicated that labeling indices increased significantly in proximal tubules (17 times) and endothelial cells (4 times) in the outer renal medulla of treated mice compared to controls. Nuclear areas in these cells also increased significantly. Our studies demonstrated a time course of new DNA synthesis stimulated by a renotropin and identified renotropin target cells.

Effect of ageing on cyclic AMP output by renal medullary cells in response to arginine vasopressin in vitro in C57BL/Icrfat mice

The effect of age on the cyclic AMP (cAMP) response to increases in the concentration of arginine vasopressin in the presence of isobutyl methylxanthine (100 mumol/l) was studied in an in-vitro renal cell suspension prepared from C57BL/Icrfat mice at 6, 12, 18, 24, 29 and 35 months of age. Comparison of the response of the preparation to vasopressin, calcitonin and parathyroid hormone suggested that it was enriched with renal medullary cells. Basal cAMP output was similar throughout but the threshold dose of vasopressin increased from 1 X 10(-11) mol/l (6, 12 and 18 months of age) to 1 X 10(-10) mol/l (24, 29 and 35 months of age). The dose-response curve in 35-month-old mice was shifted to the right with the concentration of vasopressin required to give half maximal cAMP increased from 9.4 +/- 0.37 X 10(-11) mol/l (6 months) to 3.5 +/- 1.6 X 10(-10) mol/l (35 months). Maximum cAMP output at 1 X 10(-9) mol/l was also reduced in the same animals (stimulated:basal ratio, 51.22 +/- 19.12 at 6 months; 11.50 +/- 6.02 at 35 months). The results suggest that the lack of renal response to vasopressin in terms of cAMP metabolism may play a role in the well-documented age-related decline in urine-concentrating ability in experimental animals and elderly people.

Immunohistochemical localization of a protein fraction derived from rabbit renal papilla

Studies were carried out to define antigenic characteristics of the rabbit renal collecting duct. Renal papillae of adult rabbits were homogenized, centrifuged, and the 600 X g pellet was extracted with 0.5% Triton X-100 in the presence of 1 M NaCl. The crude extract was fractionated on an anion exchange column (DEAE cellulose). A fraction enriched in acidic proteins that co-purified with a radioactive 150 kd glycoprotein from cultured collecting duct cells (Minuth 1982), was used for immunization of guinea pigs. The antiserum shows the following characteristics as revealed by indirect immunofluorescence on the rabbit kidney: 1) Among all tubular epithelial cells only principal cells of the collecting duct and the connecting tubule cell show immunoreactivity. 2) The antiserum decorates the epithelial-interstitial interface of the whole collecting duct as well as of connecting tubule and thick ascending limb of Henle's loop. 3) There is immunoreactivity of interstitial fibers throughout the kidney. 4) Epithelial cells in a variety of other organs in rabbit did not react with the antiserum. Our data demonstrate an antigenic distinction of both, the connecting tubule cell and the principal cell, discriminating these cells from other tubular epithelial cells including the intercalated cells of the collecting duct system. Furthermore, our findings point to a heterogeneity along the distal nephron with respect to the constituents of the epithelial-interstitial interface.

Antihypertensive polar and neutral renopapillary lipids. Which is a hormone?

Two antihypertensive lipids can be derived from the renal papilla, the antihypertensive polar (APRL) and the antihypertensive neutral (ANRL) renomedullary lipid. The renal venous effluent of the unclipped kidney contains both ANRL and APRL. This effluent lowers the arterial pressure (AP) of the normal rat when infused i.v. As it lowers the AP the heart rate (HR) and sympathetic nerve activity (SNA) are depressed. ANRL infused i.v. also lowers HR and SNA as it depresses the AP. Conversely, APRL elevates HR and SNA as it lowers the AP. Thus, of the two lipids in the renal venous effluent after unclipping, ANRL appears to be dominant. APRL, however, in the renal venous effluent could potentiate the action of ANRL. The net effect of these observations is to support the view that ANRL is an antihypertensive hormone liberated by the kidney after unclipping. The renomedullary interstitial cells (RIC) degranulate after unclipping. ANRL can be derived from these cells. Thus, the RIC, cells known to exert an endocrine-type antihypertensive function, may well be the source of ANRL in the renal venous effluent after unclipping. The hormonal action of ANRL appears as a major cause of the lowering of the AP after unclipping. It is not known what factors modulate the RIC endocrine system. There is a suggestion that angiotensin may be one of these factors based on the ineffectiveness of these cells toward retarding hypertension when the circulating plasma angiotensin level is high, and their effectiveness when the circulating plasma angiotensin level is low.

Proliferation-stimulating effect of phenacetin on the urothelium and papillary epithelium of rats

In the present autoradiographic study, the effect of phenacetin (PH) on the proliferative activity of the urothelium and epithelium lining the renal papilla of rats was tested. The median 3H-thymidine-labeling index (3H-TdR index) of the bladder urothelium of rats daily fed PH for 2 years was twofold increased compared to untreated or initially partially cystectomized rats. The median 3H-TdR index of the papillary epithelium was 2-3 times higher than in untreated controls. The transitional epithelium of the renal pelves showed an approximately 2 times, and the urothelium of the ureters a 3 times increased median 3H-TdR index only when PH administration was combined with an initial one-third resection of the urinary bladder. Since after PH treatment the highest DNA synthesis consistently occurred in all rats with a resected bladder, it can be concluded that partial cystectomy increases the ability of the urothelium and the papillary epithelium to proliferate in response to the drug. The proliferation-stimulating effect of PH can be reconciled with a cocarcinogenic or promoting activity of the drug.

Morphometric studies of the renomedullary interstitial cells of Dahl hypertension-prone and hypertension-resistant rats

Two strains of rats, one genetically sensitive (the Dahl S rat) and the other resistant (the Dahl R rat) to the hypertensive effect of a high-salt diet were studied morphometrically for determination of whether any anatomic differences were present in the renomedullary interstitial cells (RICs) that might help explain these strain differences. The rats resistant to the hypertensive effects of sodium chloride had more RIC than those from the sensitive strain. In addition, they were more heavily granulated. These findings may be related to the known antihypertensive function of the RICs and may help explain observed differences in the prostaglandin metabolism of the Dahl S and R rats.

Altered cyclic AMP responsiveness to vasopressin in rat renal medullary dispersed cells by acute elevation of endogenous vasopressin

Medullary and cortical tubular cells were prepared from rat kidneys with collagenase treatment. Arginine vasopressin (AVP) stimulated cyclic AMP production both in medullary and cortical cells with a dose-response relationship at concentrations ranging from 10 microU/ml to 10 mU/ml, whereas parathyroid hormone (PTH) and calcitonin did only in the latter. Using this medullary cell system, effects of acute changes in endogenous plasma AVP levels in vivo on its cyclic AMP responsiveness to AVP (10 mU/ml) in vitro were examined. Acute elevation of plasma AVP levels induced by ip injection of 20% (w/v) polyethylene glycol-isotonic saline solution 3 h prior to sacrifice resulted in a 33% decrease in cyclic AMP responsiveness to AVP (desensitization). More prolonged elevation of plasma AVP levels by water restriction for 48 h, on the other hand, increased the responsiveness by 38 to 81%, which was restored to basal levels by ad libitum intake of water for another 48 h (positive feedback regulation). These maneuvers did not alter the cyclic AMP responsiveness to PTH (10 micrograms/ml) in cortical cells. The results suggest that AVP-stimulated adenyl cyclase in rat renal medulla may be regulated by changes in endogenous AVP levels even within the physiological range.

Immunocytochemical localization of Na+, K+-ATPase in the rat kidney

To determine if rat kidney Na+, K+-ATPase can be localized by immunoperoxidase staining after fixation and embedding, we prepared rabbit antiserum to purified lamb kidney medulla Na+, K+-ATPase. When sodium dodecylsulfate polyacrylamide electrophoretic gels of purified lamb kidney Na+, K+-ATPase and rat kidney microsomes were treated with antiserum (1:200), followed by [125I]-Protein A and autoradiography, the rat kidney microsomes showed a prominent radioactive band coincident with the alpha-subunit of the purified lamb kidney enzyme and a fainter radioactive band which corresponded to the beta-subunit. When the Na+, K+-ATPase antiserum was used for immunoperoxidase staining of paraffin and plastic sections of rat kidney fixed with Bouin's, glutaraldehyde, or paraformaldehyde, intense immunoreactive staining was present in the distal convoluted tubules, subcapsular collecting tubules, thick ascending limb of the loops of Henle, and papillary collecting ducts. Proximal convoluted tubules stained faintly, and the thin portions of the loops of Henle, straight descending portions of proximal tubules, and outer medullary collecting ducts did not stain. Staining was confined to basolateral surfaces of tubular epithelial cells. No staining was obtained with preimmune serum or primary antiserum absorbed with purified lamb kidney Na+, K+-ATPase, or with osmium tetroxide postfixation. We conclude that the basolateral membranes of the distal convoluted tubules and ascending thick limb of the loops of Henle are the major sites of immunoreactive Na+, K+-ATPase concentration in the rat kidney.

Cellular swelling in slices of rat renal outer medulla incubated in the presence of bovine serum albumin

1. Cells in slices of rat renal outer medulla incubated for up to 100 min in modified phosphate-bicarbonate Ringer undergo reversible, concentration-dependent swelling (increase in water content) in the presence of bovine serum albumin (b.s.a). 2. Swelling also takes place in the presence of dextran sulphate, but neutral dextran or polyvinylpyrrolidone are without effect. 3. Swelling due to b.s.a. is pH-dependent, decreasing (relative to cell volume in the absence of b.s.a.) as pH is reduced. 4. Swelling due to b.s.a. is associated with the net cellular gain of Na+, the magnitude of which increases at pH is raised. 5. There is an accompanying pH-independent net loss of cellular K+; at pH greater than about 6.20 this loss is smaller than the uptake of Na+, and cells thus show net gain of monovalent cation. 6. The relationships between pH and percentage increase in cell water content and between pH and percentage increase in cell osmotic content due to net gain of cation in the presence of 8% b.s.a. are coincident within the range pH 6.15--7.60. 7. Studies on the volume of distribution of [125I]b.s.a. within slices suggests that more may bind to cells at low pH than at high pH.

Immunohistochemical characterization of renin-containing cells in the human juxtaglomerular apparatus during embryonal and fetal development

Thirty kidneys from nine embryos, 20 fetuses, and one full-term baby were examined for their renin content by immunofluorescence and the peroxidase antiperoxidase method, using an antihuman renin antiserum. Renin-containing cells were found in the early metanephros (5-week-old fetuses). Most of them were located in the wall of well-developed renal arteries in the vicinity of the prospective vascular pole of the glomeruli. In the poorly differentiated peripheral renal cortex, intracellular fluorescence was seen in nearby arterioles of pocket-like s-shaped tubules. Rarely, labeled cells were found in the wall of major branches of renal arteries. In all locations, the renin-containing cells appear to be clearly linked to the development of the renal vascular system.

New ideas on the anatomy of the kidney

Images

Degranulation of renomedullary interstitial cells during reversal of hypertension

It was demonstrated earlier that the renal venous effluent of one-kidney, one clip hypertensive rats contained a vasodepressor lipid resembling the antihypertensive neutral renomedullary lipid (ANRL), following unclipping and as the arterial pressure (MAP) was lowered. Consequently, the sham-unclipped (clip-intact) and the unclipped kidney (CK and UCK) were studied by electronmicroscopy and morphometrically (Weibel's techniques). Renomedullary interstitial cells (RIC) of the CK had abundant granules. The collecting duct (CD) had tall lining cells containing pale granules and displayed intercellular channels. Following unclipping, the RIC degranulated and the CD cells became flattened, lost their pale granules, and the intercellular channels disappeared as the MAP decreased. These changes were evident by EM appearance and volume density measurements. The renopapillary changes occurred as the kidney secreted the ANRL-like substance into the blood.

Studies on the relationship between rat renal medullary cell volume and external anion concentration in hyperosmolal media

1. The volumes of cells in slices of rat renal outer medulla have been examined following incubation or 25 min in hyperosmolal media (650 and 950 m-osmole/kg H2O) containing independently variable concentrations of Cl (70-325 mM) and HCO3 (10-60 mM) (gas phase 95% O2/5% CO2). 2. For any given level of external Cl concentration cell volumes were reduced by increasing the external HCO3 concentration. These reductions were accompanied by net loss of cellular K and Cl. In confirmation of earlier findings, cell volumes were also reduced by increasing external Cl concentration. 3. Experiments in which the HCO3 concentration and pH of the incubation media were independently varied by the use of N-2-hydroxyethylpiperazine-N'-2-ethanesulphonic acid (HEPES)/100% O2 showed that it is the HCO3 anion per se which influences cell volume. 4. The anion exchange inhibitor 4-acetamido-4'-isothiocyanatostilbene-2,2'-disulphonic acid (SITS, disodium salt, 1 mM) abolished the dependence of cell volume upon HCO3 but not upon Cl. 5. Acetazolamide (1 mM) influenced (reduced) cell volumes only in the presence of low (10 mM) HCO3. 6. CNS (25 mM) also markedly reduced cell volumes in media containing 10mM-HCO3 and, to a lesser extent, 25 mM-HCO3. It was without effect on cell volume when external HCO3 was 60 mM. 7. The presence of CNS was associated with the significant cellular net accumulation of Cl in media in which either Cl or HCO3 concentration (or both) was low (70 or 130 mM and 19 mM respectively). 8. The outer medullary [35S]CNS space at 25 min, determined for slices incubated in a representative selection of the various media employed in this study, exceeded the [14C]inulin space by 1.77 microliters/10 mg wet weight.

The effect of arginine vasopressin and its analogs on the synthesis of prostaglandin E2 by rat renal medullary interstitial cells in culture

Arginine vasopressin (AVP) stimulates renal prostaglandin (PG) production which is thought to inhibit vasopressins' antidiuretic action. Using rat renal medullary cells in culture (RMIC), we compared the ability of the following peptides which possess different biological activities to stimulate prostaglandin biosynthesis: AVP (high antidiuretic and pressor activities); 1-desamino-8-D-arginine vasopressin (a synthetic peptide with high antidiuretic and no pressor activity); and oxytocin (intermediate pressor, low antidiuretic activity). Radiometric thin-layer chromatography of supernatant media from cells incubated with octatritiated or [14C]arachidonic acid revealed only one radiolabeled peak which co-migrated with PGE2. Radioimmunoassay confirmed that PGE2 was the only prostaglandin synthesized by RMIC. Incubation of cells with AVP (1 nM to 3 microM) increased PGE2 synthesis measured by radioimmunoassay in a concentration-dependent fashion up to 2 1/2-fold over control; 1-desamino-8-D-arginine did not increase PGE2 synthesis. Oxytocin stimulated PGE2 synthesis, but was less potent than AVP. Preincubation of RMIC with [1-(beta-mercapto-beta, beta-cyclopentamethylene propionic acid)-4-valine, 8-D-arginine]vasopressin, a synthetic nonpressor, nonantidiuretic antagonists of AVP's pressor activity, completely blocked the ability of AVP to stimulate PGE2 synthesis. We conclude that the ability of AVP to stimulate PGE2 synthesis in RMIC is related to its pressor, not its antidiuretic, activity.

Renomedullary deficiency in partial nephrectomy-salt hypertension

Partial nephrectomy-salt hypertension (PN-SH) of the rat is associated with Na volume loading. As the hypertensive state evolves, the renomedullary interstitial cells (RIC) of the renal nubbin undergo major changes, decreasing significantly in number while the remaining ones exhibit degenerative changes. The antihypertensive action of the RIC in the renal nubbin, as measured by transplants of fragmented papillae into hypertensive recipients, virtually disappears as the hypertension develops. The changes in the RIC occur whether vascular disease of the kidney is or is not overtly present. It is suggested that deficiency of the antihypertensive action of the RIC allows the prohypertensive effects of Na volume loading to operate without proper control. Thus, the sustained hypertensive state of this model does not appear to be due solely to volume expansion. Rather, it appears due to a combination of the effects of Na and volume and a renomedullary deficiency of hormonal type. The specific cause(s) of the changes in the RIC was not determined. It seems evident that it is related to the high salt intake since the partial nephrectomy procedure without the added salt load did not alter the appearance of the RIC.