enal failure is a common and serious glycosylated protei] complication of longstanding diabetes vasoactive hormon mellitus. Diabetes is now the most common ular hypertension, I cause of end-stage renal failure requiring tors, and cytokines dialysis in the United States, accounting for the pathogenesis c almost 40% of all new dialysis patients (1). (10, 11). Of these, th Moreover, the incidence of renal failure growth factor (TGF caused by diabetes, particularly type II diaing a key role in th betes, is rising dramatically worldwide (2). hypertrophy and ac Compounding the tragedy of the explosive lular matrix in diab growth in the incidence renal failure caused known to have pov by diabetes is the grim reality that the surresulting from bot] vival of patients with renal failure caused by synthesis and inhib: diabetes is much worse than that of patients tion (12). In huma with renal failure resulting from other TGF-P mRNA ane causes. In Germany, for example, Koch et al. nificantly increasec (3) reported a 5-year survival of only 5% tubulointerstitium among patients with type II diabetes underMoreover, short-t( going dialysis. Fortunately, progress is being TGF-3 neutralizing made in our understanding of the pathochemically induced genesis of diabetic renal disease and in our merular enlargeme ability to delay, or even prevent, this devasexpression of gene, tating complication. Two studies appearing matrix components in this issue of PNAS (4, 5) are illustrative of by Ziyadeh et al. (4 this progress. Diabetic nephropathy refers extends these obser to a characteristic set of structural and funcstrongest evidence t tional kidney abnormalities that occur in of TGF-P in the sl patients with diabetes. Although best deabnormalities of di; scribed in patients with type I diabetes (6), Specifically, Ziya similar findings are now known to occur in the effects of long-t the more common type II diabetic patient neutralizing TGF-f (7). Structural abnormalities include hyperfunction and rena trophy of the kidney, an increase in the mice. These mice, t thickness of glomerular basement memhypothalamic leptii branes, accumulation of extracellular matrix obesity caused by ( corrponents in the glomerulus (nodular and tance, and hypergly diffuse glomerulosclerosis), tubular atrothe dbldb mouse phy, and interstitial fibrosis (6, 7). Funcdiabetes mellitus, w tional alterations include an early increase 70-80% of all diab in the glomerular filtration rate with intraure (1). Kidneys fro glornerular hypertension, subsequent proexhibited an increa teinuria, systemic hypertension, and evenpression in glomer tual loss of renal function (8). TGF-3 receptor exi Clinicopathologic studies of diabetic newith nondiabetic c phropathy have established that the extent larly, there was an of matrix accumulation in both the glomerIV collagen al anc uli and the interstitium correlate strongly pression and histol with the degree of renal insufficiency and gial matrix expans proteinuria (9). Accordingly, the factors reFunctional abnorn sponsible for the deposition and accumulaphropathy includet tion of extracellular matrix material within merular filtration r

First World Congress of Nephrology October 13, 2001 Colleagues and guests, welcome to this first World Congress of Nephrology in San Franciso. Robert J. Alpern, President of the American Society of Nephrology, will introduce the members of the Council of the American Society of Nephrology and the Program Director: Thomas H. Hostetter, Roland C. Blantz. John B. Stokes, Norman J. Siegel, William E. Mitch, Tomas Berl, Thomas D. DuBose, and Qais Al-Awqati. The members of the Executive Committee of the International Society of Nephrology and the Program Director for this Congress include Robert C. Atkins from Australia, Jan J. Weening from The Netherlands, Rashad S. Barsoum from Egypt, William E. Mitch from the United States, Saulo Klahr from the United States and Editor of Kidney International, and Steven C. Hebert from the United States. Ordinarily, meetings of the International Society of Nephrology or the American Society of Nephrology are academic celebrations laden with high scholarship, festive collegiality, the renewal of old friendships, and the formation of new bonds with colleagues. But our enthusiasm today is muted by the apocalyptic tragedy of September 11, 2001, which has cast a bleak penumbra over our planet. The terrorist acts were directed primarily against the United States, but they assassinated people from more than 60 countries. They are a direct affront to justice and simple decency, two of the key pillars of civilized societies. The acts, in fact, are better termed heinous crimes than terrorist acts. These crimes are a particular affront to those of us assembled here, since our lives are dedicated to healing, not killing. Thus, all of us share jointly in mourning our losses and in mourning what will inevitably be a certain curtailing of all our individual freedoms. In tribute to those people from more than 60 nations who were murdered on September 11, and to people murdered in all such criminal acts, I ask that you stand for a moment of silence. What will happen after we have buried those who fell? There are some who believe that we cannot recover from the tragic events of September 11, 2001. I am certain that we can, and we will. In the past century, we saw unimaginable horrors: Stalin, the Katyn Forest; Hitler and Eichmann, the Holocaust; and Pol Pot and the Khmer Rouge, genocide in Cambodia. But even with these horrors, the vector of humanity moves forward inexorably. There are, after all, more people free on our planet now than in the entire history of the world. I find solace in the last paragraph of William Faulkner's 1950 Nobel Prize Address, written shortly after the end of World War II, at the height of the Cold War, and with the Korean conflict about to occur. The most memorable passage from that paragraph is “I believe that man will not merely endure: He will prevail… He alone among creatures has an inexhaustible voice, a soul, a spirit capable of compassion and sacrifice and endurance.” I hope Faulkner's affirmation of humanity's strengths benefits you as much as it has me. Finally, with regard to September 11, I am happy to announce that the American Society of Nephrology and the International Society of Nephrology will each make a $5000 donation to the American Red Cross to aid that organization in its efforts in New York, Washington, and Pennsylvania. I turn now to more felicitous comments, all related to this first World Congress. The International Society of Nephrology was an outgrowth of the vision of Jean Hamburger, the founder of the Nephrology Unit at the Necker Hospital in Paris. Professor Hamburger organized a series of meetings with international colleagues that began in 1957 and culminated in the first International Congress of Nephrology in Evian-Les-Bains in 1960. Ike Robinson and Gabriel Richet, both Past Presidents of the International Society of Nephrology, have provided a detailed account of the genesis of the International Society of Nephrology in their supplement to the June 2001 issue of Kidney International. This brief excerpt from Hamburger's writings explains his reasoning for forming the International Society of Nephrology: “It is clear to see why there are so many who see in nephrology one of the blossoms … responsible for … revolutionary progress… It is natural that all these lovers of research on healthy and diseased kidneys decided … to establish among themselves a bond of friendship and work—La Société International de Néphrologie.” When the first meeting of the International Society of Nephrology was held in Evian-les-Bains, there were slightly more than 400 participants. At the time, there were only four societies that focused specifically on the study of renal function and renal diseases: La Société de Néphrologie in France, the Renal Association of Great Britain, the Scandinavian Society for Kidney Research, and the Societa Italiana di Nefrologia. When the International Society of Nephrology was formed, Jean Hamburger's concept was of an academically elite organization whose cardinal purpose was to exchange scientific information. And what was nephrology at the time? Hemodialysis for acute renal failure was limited in scope everywhere. Chronic dialysis was nascent, guided by the heroic trials of Belding Scribner in Seattle. Renal transplantation was in its infancy, involving largely living related donor transplantation with cadaveric transplantation in an experimental stage. And the major immunosuppressive modalities available for renal transplantation were azathioprine, prednisone, and radiation. In renal physiology, we had just come to recognize the power of Carl Gottschalk's concepts for countercurrent multiplication. Ideas about the regulation of renal blood flow, glomerular filtration, tubuloglomerular feedback, the proximal nephron, and the prismatic functions of the collecting duct were, to say the least, vague. Renal biopsy was a new discipline. Renal arteriography was hazardous. And ultrasound, CT scans, and MRI scans were nonexistent. With respect to nephropathies, the Dixon models for immune renal injury, either immune complex or antiglomerular basement membrane antibody disease, were the cardinal paradigms for immunologic renal disease. And many believed that as many as 30% of the population had evidence of pyelonephritis at autopsy, a notion later dispelled elegantly by Paul Kimmelsteil. A perusal of the program for this World Congress provides abundant testimony to the fact that, in the last 40 years, nephrology has grown exponentially. We understand many of the subtleties of how nephrons work and many of the complexities of immune renal disease. Renal transplantation and dialysis are now routine. We understand that most forms of hypertension may be renal in origin, a concept first articulated by Richard Bright in the early 1800s. And happily, we now have effective therapeutic strategies for treating hypertension of renal and nonrenal origin. The number of students of nephrology has also grown dramatically. There are now over 95 national and regional societies of nephrology throughout the world, all concerned with the study of renal function and dysfunction, and all committed to improving the lot of patients afflicted with renal disease. Why a World Congress of Nephrology? The answer lies in the remarkable clarity of thought of Ike Robinson, President of the American Society of Nephrology in 1982, and President of the International Society of Nephrology from 1990 to 1993. Ike saw that many national meetings, most notably that of the American Society of Nephrology, had already acquired an international flavor. Ike was therefore concerned that we might be entering an era where few of us had either the time or the resources to attend multiple meetings. He proposed that future International Society of Nephrology meetings might be coupled to meetings of national or regional societies. For these reasons, negotiations between the American Society of Nephrology and International Society of Nephrology for today's meeting began in 1993. Happily, because of the cordiality of Bob and his colleagues, past and present, on the American Society of Nephrology Council, these negotiations have been exceedingly successful and remarkably pleasant. There are over 10,000 registrants representing more than 100 nations in this first World Congress of Nephrology. The number of abstracts submitted, in excess of 5000, is nearly the sum of the total number of abstracts submitted to the 1999 International Society of Nephrology Congress in Buenos Aires and to the 2000 American Society of Nephrology meeting in Toronto. So, at least quantitatively, we have done well. The quality of the meeting, of course, will be judged by you. Finally, with particular respect to the International Society of Nephrology, I return to Hamburger's original view of the International Society of Nephrology as an elitist organization concerned with the exchange of high science. The International Society of Nephrology, like all organizations, is a tapestry which has not been and, I hope, never will be completed. The International Society of Nephrology has, without doubt, academic and scientific elitism, most importantly through our Congresses, through Saulo Klahr's stewardship of Kidney International, and Bob Alpern and Heini Murer's guidance of the Forefronts in Nephrology series, which have brought to nephrology a strong influx of molecular biology and, now, genomics and proteomics. At the same time, the International Society of Nephrology must be egalitarian, both personally and intellectually, genuinely global in scope, and prismatic in content. And the International Society of Nephrology has come to recognize its responsibility for fostering education, clinical growth, and truly global participation. Some examples of the contributions to these ideals include the Committee for the Global Advancement of Nephrology, the so-called COMGAN program, organized splendidly by Barry Brenner and John Dirks; the International Fellowship Program, assembled with characteristic grace and dignity by the late Claude Amiel, and which has now provided training for nearly 300 fellows from 55 countries hosted in 16 countries, and all pledged to return to their native countries; the Renal Sister Center Program, initiated in 1997 by Robert Schrier, is now directed by Rashad Barsoum and Eberhard Ritz, constitutes 146 Sister Centers involving 89 countries. This World Congress of Nephrology also shows that we have become global conceptually. There is something for everyone at this meeting, whether you are a molecular biologist, a physiologist, an immunologist, or a clinical nephrologist concerned particularly with dialysis and transplantation. I, therefore, believe that our two societies are moving in the right direction for achieving an appropriate balance between academic excellence, clinical excellence, and a genuine world presence. I close by expressing my sincere thanks again to Dr. Alpern and his colleagues on the Council of the American Society of Nephrology for joining us in this venture, and for making a potentially difficult set of arrangements remarkably pleasant. I also thank, with genuine gratitude, Qais Al-Awqati, Steve Hebert, and their colleagues on the Program Committee. You will judge the quality of their efforts as the Congress unfolds.

Cl- channels in basolateral TAL membranes. XVI. MTAL and CTAL cells each contain the mRNAs encoding mmClC-Ka and mcClC-Ka.

AbstractThe sections in this article are:The Water‐Repletion ReactionCell‐Volume RegulationThe NeurohypophysisStructureHormone Biosynthesis, Transport, and MetabolismControl of Antidiuretic Hormone ReleaseOsmotic RegulationNonosmotic RegulationChemical MediatorsIntranuclear SecretionOxytocinThirstOsmotic RegulationVolume‐Mediated ThirstSatiation of ThirstRenal Contribution to Osmotic HomeostasisRenal Countercurrent MechanismsEffects of Filtration Rate and Solute ExcretionCollecting TubuleMedullary Thick Ascending Limb of HenleIntegration of Antidiuretic Hormone Actions with the Urinary Concentrating MechanismSelected Clinical Derangements of Water BalanceHypertonic SyndromesHypotonic Syndromes

A unique property of basolateral membrane Cl- channels from the mTAL is that the Cl- concentration facing the intracellular aspects of these channels is a determinant of channel open time probability (Po). The K1/2 for maximal activation of Po by Cl- facing intracellular domains of these channels is 10 mM Cl-. The present experiments evaluated the nature of these Cl(-)-interactive sites. First, we found that the impermeant anion isethionate, when exposed to intracellular Cl- channel faces, could augment Po with a K1/2 in the range of 10 mM isethionate without affecting conductance (gCl, pS). Second, pretreatment of the solutions facing the intracellular aspects of the channels with either 1 mM phenylglyoxal (PGO), an arginine-specific reagent, or the lysine/terminal amine reagent trinitrobenzene sulfonic acid (TNBS, 1 mM), prevented the activation of Po usually seen when the Cl- concentration of solutions facing intracellular channel domains was raised from 2 to 50 mM. However, when the Cl- channel activity was increased by first raising the Cl- concentration bathing intracellular channel faces from 2 to 50 mM, subsequent addition of either PGO or TNBS to solutions bathing intracellular Cl- channel faces had no effect on Po. We conclude that the intracellular aspects of these Cl- channels contain Cl(-)-interactive loci (termed [Cl]i) which are accessible to impermeant anions in intracellular fluids and which contain arginine- and lysine-rich domains which can be inactivated, at low ambient Cl- or isethionate concentrations, by interactions with PGO or TNBS.

Cl− channels from basolaterally-enriched rabbit outer renal medullary membranes are activated either by increases in intracellular Cl− activity or by intracellular protein kinase A (PKA). Phosphorylation by PKA, however, is not obligatory for channel activity since channels can be activated by intracellular Cl− in the absence of PKA. The PKA requirement for activation of Cl− channels in certain secretory epithelia is, in contrast, obligatory. In the present studies, we examined the effects of PKA and intracellular Cl− concentrations on the properties of Cl− channels obtained either from basolaterally-enriched vesicles derived from highly purified suspensions of mouse medullary thick ascending limb (mTALH) segments, or from apical membrane vesicles obtained from two secretory epithelia, bovine trachea and rabbit small intestine. Our results indicate that the Cl− channels from mTALH suspensions were virtually identical to those previously described from rabbit outer renal medulla. In particular, an increase in intracellular (trans) Cl− concentration from 2 to 50 mm increased both channel activity (Po) and channel conductance (gCl, pS). Likewise, trans PKA increased mTALH Cl− channel activity by increasing the activity of individual channels when the trans solutions were 2 mm Cl. Under the latter circumstance, PKA did not activate quiescent channels, nor did it affect gCl. Moreover, when mTALH Cl− channels were inactivated by reducing cis Cl− concentrations to 50 mm, cis PKA addition did not affect Po. These results are consistent with the view that these Cl− channels originated from basolateral membranes of the mTALH.

The sections in this article are: 1 Theoretical Foundations of Water Transport in Epithelia 2 Volume Absorption in the Proximal Tubule 3 Water Permeability of the Proximal Tubule 3.1 Measurement of Water Permeability 3.2 Importance of the Osmotic Water Permeability 4 Location of the Osmotic Gradient 4.1 Luminal Hypotonicity Produced by Solute Absorption 4.2 Absorbate Hypertonicity 5 “Passive” Driving Forces for Volume Absorption 5.1 NaCl Diffusion in Volume Absorption 5.2 Reflection Coefficient Differences 6 Models of Solute-Solvent Coupling in Proximal Volume Absorption 7 Routes of Volume Movement in the Proximal Nephron 7.1 Measurement of Cell Membrane Osmotic Water Permeabilities 8 Consequences of Transcellular Volume Flow 9 The ADH-Sensitive Distal Nephron 9.1 Measurement of Permeability Changes Produced by ADH 9.2 Wafer Permeability of ADH-Sensitive Nephron Segments in Vivo and in Vitro 10 Site of the Change in Water Permeability with ADH 11 Evaluation of the Pf/PDw Ratio 11.1 Large Pore Hypothesis 11.2 Unstirred Layer Effects 12 The Narrow Channel Hypothesis: Single-File Diffusion Through Small Aqueous Channels 13 ADH Increases the Number of Narrow Aqueous Channels in Apical Plasma Membranes 14 The Apparent EA for Water Transport in Cortical Collecting Tubules 14.1 The Raw Data 14.2 Correction for Diffusion Constraints in Series with Apical Membranes 14.3 The “True” EA for Water Transport 15 Pseudo-“Breaks” in EA Measurements 16 Comparison of ADH-Dependent Apical Membrane Water Channels with Gramicidin A Channels 17 Parallel Paths for Water and Solute Permeation 18 Morphologic Studies 19 Intracellular Mediators of ADH Action 19.1 Modulation of ADH Action—α-Adrenergic Agents 19.2 Atrial Natriuretic Peptide 20 Prostaglandins 20.1 Calcium 20.2 Protein Kinase C 21 Summary

We examined the interactions of cAMP-dependent protein kinase and varying aqueous Cl- concentrations in modulating the activity of Cl- channels obtained by fusing basolaterally enriched renal outer medullary vesicles into planar lipid bilayers. Under the present experimental conditions, the cis and trans solutions face the extracellular and intracellular aspects of these Cl- channels, respectively. Raising the trans Cl- concentration from 2 to 50 mM increased the channel open-time probability, raised the unit channel conductance, and affected the voltage-independent determinant (delta G) of channel activity but not the gating charge (Winters, C.J., Reeves, W.B., Andreoli, T.E. 1990. J. Membrane Biol. 118:269-278). With 2 mM trans KCl, trans addition of the catalytic subunit of PKA (C-PKA) plus ATP increased channel open-time probability and altered the voltage-independent determinant of channel activity without affecting either unit channel conductance or gating charge. The effect was ATP specific, did not occur with (C-PKA plus ATP) addition to cis solutions, and was abolished by denaturing C-PKA. Finally, (C-PKA plus ATP) activation of channel activity was not detected with relatively high (50 mM) trans Cl- concentrations. These data indicate that (C-PKA plus ATP) might modulate Cl- channel activity by phosphorylation at or near the Cl(-)-sensitive site on the intracellular face of these channels.

This paper provides the results of studies which characterized conductive36Cl− flux in basolaterally enriched membrane vesicles prepared from rabbit renal outer medulla. Conductive36Cl− uptake was studied under two different experimental conditions. In the first,36Cl− flux was driven by an inside positive voltage created with oppositely directed Cl− and gluconate gradients. In the second, an inwardly direct K+ gradient was used to drive36Cl− uptake. By these two methods, voltage-sensitive36Cl− uptake was shown to comprise about 45 and 65%, respectively, of the initial rates of total36Cl− flux. Separate paired studies demonstrated that the conductive36Cl− uptake was inhibited by the Cl− channel blocker diphenylamine-2-carboxylate (DPC) with an IC50 for DPC of 154 μm. The voltagedependent36Cl− uptake had an activation energy of 6.4 kcal/mole. This36Cl− conductance had an anion selectivity sequence of I−>Cl−≧NO 3 − ≫gluconate.

We evaluated the effects of vawrying aqueous Cl− concentrations, and of the arginyl- and lysyl-specific reagent phenylglyoxal (PGO), on the properties of Cl− channels fused from basolaterally enriched renal medullary vesicles into planar lipid bilayers. The major channel properties studied were the anion selectivity sequence, anionic requirements for, channel activity. and the efects of varying Cl− concentrations and/or PGO on the relation between holding voltageV H -mV) and open-time probability (Po).

ADH, acting through cAMP, increases the potassium conductance of apical membranes of mouse medullary thick ascending limbs of Henle. The present studies tested whether exposure of renal medullary apical membranes in vitro to the catalytic subunit of cAMP-dependent protein kinase resulted in an increase in potassium conductance. Apical membrane vesicles prepared from rabbit outer renal medulla demonstrated bumetanide-and chloride-sensitive22Na+ uptake and barium-sensitive, voltage-dependent86Rb+-influx. When vesicles were loaded with purified catalytic subunit of cAMP-dependent protein kinase (150 mU/ml), 1mm ATP, and 50mm KCl, the barium-sensitive86Rb+ influx increased from 361±138 to 528±120pm/mg prot · 30 sec (P<0.01). This increase was inhibited completely when heat-stable protein kinase inhibitor (1 μg/ml) was also present in the vesicle solutions. The stimulation of86Rb+ uptake by protein kinase required ATP rather than ADP. It also required opening of the vesicles by hypotonic shock, presumably to allow the kinase free access to the cytoplasmic face of the membranes. We conclude that cAMP-dependent protein kinase-mediated phosphorylation of apical membranes from the renal medulla increases the potassium conductance of these membranes. This mechanism may account for the ADH-mediated increase in potassium conductance in the mouse mTALH.

The specialized transport properties of the thick ascending limb of Henle's loop (TALH) enable this segment of the nephron to dissociate salt and water absorption. Sodium chloride absorption by the cortical (cTALH) and medullary (mTALH) thick ascending limb accounts for urinary dilution, since each of these segments is virtually water–impermeable. Salt absorption by the mTALH also contributes to medullary interstitial hypertonicity, supplies the energy for the single effect of countercurrent multiplication, and hence modulates urinary concentrating mechanisms. The medullary (mTALH) and cortical (cTALH) portions of the TALH are clearly heterogeneous, and can be distinguished on the basis of morphological [1, 2], biochemical [3–6] and functional [7] differences. This article will focus particularly on the transport functions of the medullary segment. The specific issues discussed will include the mechanism of NaCl absorption by the mTALH, the enhancement of this salt absorptive process by antidiuretic hormone (ADH), at least in certain mammalian species, and the major factors that appear to regulate or modulate both ADH-dependent and -independent NaCl transport processes. Sufficient information is currently available which indicates that these modulating factors provide feedback loops which sense interstitial osmolality and serve as a means of controlling the magnitude of interstitial hypertonicity, and hence concentrating power.