Acidification adaptation in cultured inner medullary collecting duct cells

1993 ◽  
Vol 264 (5) ◽  
pp. F765-F769 ◽  
Author(s):  
R. Mankus ◽  
J. H. Schwartz ◽  
E. A. Alexander
Keyword(s):  
Lucifer Yellow ◽  
Collecting Duct ◽  
C Cells ◽  
Inner Medullary Collecting Duct ◽  
Pump Activity ◽  
Collecting Duct Cells ◽  
Medullary Collecting Duct ◽  
New Protein

Chronic acid feeding stimulates the rat inner medullary collecting duct (IMCD) to increase acid secretion in vivo (acidification adaptation), but the mechanism for this phenomenon is unknown. Our purpose was to determine whether IMCD cells undergo adaptation in vitro and to explore the mechanism of this response. Confluent cultured rat IMCD cells were exposed to incubation media supplemented with 10(-7) M deoxycorticosterone acetate, pH 7.0 [acid incubated (AI)] or 7.7 [control (C)], for 48 h, and cell pH (pHi) was determined using 2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein. Resting pHi was 7.46 +/- 0.05 for AI and 7.25 +/- 0.04 for C (P < 0.05). N-ethylmaleimide-sensitive pHi recovery after an acute acid pulse was 0.030 +/- 0.002 for AI and 0.020 +/- 0.002 pH U/min for C (P < 0.05). However, when AI and C cells were incubated with 7 x 10(-6) M cycloheximide, the increment in pHi and enhanced proton pump activity was abolished. In addition, exocytic function, as measured by Lucifer yellow release, was increased significantly in AI cells. In summary, incubation of IMCD cells in acid medium stimulates acidification adaptation by a mechanism dependent on new protein synthesis.

Prostaglandin E2 inhibits Na+-K+-ATPase activity in the inner medullary collecting duct

1989 ◽  
Vol 257 (3) ◽  
pp. F424-F430 ◽  
Author(s):  
K. Jabs ◽  
M. L. Zeidel ◽  
P. Silva
Keyword(s):  
Atpase Activity ◽  
Prostaglandin E2 ◽  
Collecting Duct ◽  
Inner Medullary Collecting Duct ◽  
Activity Inhibition ◽  
Duct Cells ◽  
Pump Activity ◽  
Natriuretic Effect ◽  
Collecting Duct Cells ◽  
Medullary Collecting Duct

Prostaglandin E2 (PGE2) is natriuretic and inhibits collecting duct sodium transport by poorly defined mechanisms. To determine the mechanism of this inhibition, we have studied the effect of PGE2 on ouabain-sensitive (transport-dependent) oxygen consumption (QO2), ouabain-sensitive 86Rb+ uptake and ouabain-sensitive ATPase activity in fresh suspensions of rabbit inner medullary collecting duct cells, as well as Na+-K+-ATPase activity in inner medullary membranes. PGE2 (10(-5) M) reduced total QO2 by 21.6 +/- 2.3% (mean +/- SE) and reduced the ouabain-sensitive component of QO2 in IMCD cells. PGE2 failed to inhibit QO2 in the absence of sodium or in the presence of ouabain and blunted the increase in QO2 in response to amphotericin B. These results suggested that PGE2 inhibited Na+-K+-ATPase activity. Inhibition of pump activity was confirmed by measurements of 86Rb+ uptake: PGE2 (10(-5) M) reduced ouabain-sensitive 86Rb+ uptake by 57% at 10 s without altering equilibrium uptake. Furthermore, PGE2 (10(-6) M) reduced ouabain-sensitive ATPase activity by 46% in permeabilized inner medullary collecting duct cells. PGF2 alpha (10(-5) M) did not significantly alter QO2, 86Rb+ uptake, or Na+-K+-ATPase activity. These results demonstrate that PGE2 inhibits inner medullary collecting duct Na+-K+-ATPase activity and suggest a role for this inhibition in the natriuretic effect of PGE2.

HGF-mediated chemotaxis and tubulogenesis require activation of the phosphatidylinositol 3-kinase

1995 ◽  
Vol 268 (6) ◽  
pp. F1211-F1217 ◽  
Author(s):  
M. P. Derman ◽  
M. J. Cunha ◽  
E. J. Barros ◽  
S. K. Nigam ◽  
L. G. Cantley
Keyword(s):  
Collecting Duct ◽  
Collagen Matrix ◽  
Phosphatidylinositol 3 Kinase ◽  
Process Formation ◽  
High Affinity Receptor ◽  
Collecting Duct Cells ◽  
Medullary Collecting Duct ◽  
Phosphatidylinositol 3

The association of hepatocyte growth factor (HGF) with its high-affinity receptor, c-met, has been shown to induce mitogenesis, motogenesis, and morphogenesis in renal epithelial cells (L. G. Cantley, E. J. G. Barros, M. Gandhi, M. Rauchman, and S. K. Nigam. Am. J. Physiol. 267 (Renal Fluid Electrolyte Physiol. 36): F271-F280, 1994), suggesting that HGF may be critical to the orchestration of both renal development and regeneration following injury. Although signal transduction pathways activated by c-met include the phosphatidylinositol 3-kinase (PI-3-kinase), phospholipase C gamma, ras, and others, the activation of PI-3-kinase has been the most striking in vivo. We therefore investigated whether the pathways that mediate phenotypic changes in inner medullary collecting duct cells are altered by inhibition of PI-3-kinase with the fungal metabolite, wortmannin. In these cells, the mean inhibitory concentration for in vitro wortmannin inhibition of PI-3-kinase was approximately 0.2 nM. At this low concentration, motogenesis (quantified by chemotaxis) and morphogenesis (by branching-process formation within collagen matrix) were inhibited in a striking and parallel fashion, while mitogenesis was inhibited to a lesser degree. These experiments suggest that activation of PI-3-kinase is critical for c-met-mediated chemotaxis and tubulogenesis.

Kinins inhibit conductive Na+ uptake by rabbit inner medullary collecting duct cells

1990 ◽  
Vol 258 (6) ◽  
pp. F1584-F1591 ◽  
Author(s):  
M. L. Zeidel ◽  
K. Jabs ◽  
D. Kikeri ◽  
P. Silva
Keyword(s):  
Initial Rate ◽  
Collecting Duct ◽  
Physiological Effect ◽  
Na Transport ◽  
Inner Medullary Collecting Duct ◽  
Transport Effects ◽  
Collecting Duct Cells ◽  
Medullary Collecting Duct ◽  
Na Uptake

Kinins promote natriuresis in vivo, at least in part by altering Na+ transport in the collecting duct. Using freshly prepared suspensions of rabbit inner medullary collecting duct (IMCD) cells, we have examined the effects of kinins on Na+ transport using measurements of oxygen consumption (QO2) and isotopic Na+ uptake. Bradykinin (BK) inhibited IMCD cell QO2 by 24.7 +/- 0.9% without significantly reducing QO2 in cells derived from the outer medullary collecting duct. BK and kallidin half-maximally inhibited QO2 at concentrations in the 10(-12)-10-(-11) M range; beta 1-receptor agonists did not alter QO2, and beta 1-receptor antagonism did not reduce the effect of kinins. These observations indicate that the actions of kinins on IMCD cells are mediated by beta 2-receptors or a distinct subclass. Several observations indicate that kinins reduce QO2 by inhibiting Na+ entry: in the absence of Na+, BK did not reduce QO2; BK inhibition of QO2 was not additive with ouabain, amiloride, atrial natriuretic peptide (ANP), or 8-bromoguanosine 3',5'-cyclic monophosphate and was abolished in the presence of the cation ionophore amphotericin B. Measurements of isotopic Na+ uptake demonstrated that BK reduced the initial rate of Na+ entry by 58%; BK inhibited the amiloride-sensitive component of conductive Na+ uptake. Because ANP inhibits conductive Na+ entry in IMCD cells via stimulation of cGMP accumulation, the effect of BK on cGMP levels was determined. Unlike ANP, BK did not increase cGMP levels, indicating that transport effects of kinins in IMCD are not mediated by cGMP. Thus kinins directly inhibit conductive Na+ entry in IMCD cells at concentrations suggestive of a physiological effect.(ABSTRACT TRUNCATED AT 250 WORDS)

Is the function of the renal papilla coupled exclusively to an anaerobic pattern of metabolism?

1979 ◽  
Vol 236 (5) ◽  
pp. F423-F433 ◽  
Author(s):  
J. J. Cohen
Keyword(s):  
Oxidative Metabolism ◽  
Aerobic Glycolysis ◽  
Collecting Duct ◽  
High Rate ◽  
O2 Uptake ◽  
Duct Cells ◽  
Collecting Duct Cells ◽  
Mitochondrial Oxidative Metabolism

It is widely accepted that in vivo the function of the papilla of the mammalian kidney is supported primarily by anaerobic metabolism. As a result, the major source of energy for support of function in the papilla is considered to be derived from glycolysis. This orientation originates from two concepts: 1) that in vivo the gaseous environment of the papilla has such a low PO2 that O2 availability limits O2 consumption, and 2) that papillary tissue has a high rate of glycolysis when compared with either cortical tissue or extrarenal tissues. It has also been tacitly assumed that papillary tissue has a "low" O2 uptake. Review of the measurements of PO2 of papillary tissue and of urine PO2 indicates that the PO2 of papillary tissue should not limit its aerobic mitochondrial oxidative metabolism. While the rate of aerobic glycolysis in papillary tissue is high, simultaneously papillary tissue has a rate of O2 uptake similar to that of liver and higher than that of muscle. The major (two-thirds) source of energy for papillary tissue in vitro is from O2 uptake. That papillary tissue is not exclusively dependent on glucose for its energy requirements is indicated by the greater stimulation of papillary tissue QO2 by succinate than by glucose. Thus, papillary tissue has both a high aerobic mitochondrial oxidative metabolism and a high aerobic glycolytic metabolism. It is suggested that the mechanism for the high rate of aerobic glycolysis in the presence of an adequate O2 supply is due to the relatively small mass of mitochondria in papillary tissue in relation to the amount of work done by the tissue. As a result of the limited rate of ATP production by the mitochondrial electron transport chain, the phosphorylation state ([ATP]/[ADP][Pi]) is reduced and the cytoplasmic redox state ([NAD+]/[NADH]) of the papillary collecting duct cells also becomes more reduced; changes in both ratios enhance the rate of glycolysis. This limited metabolic capacity of the collecting duct cells may permit an excess volume of solute and water to be excreted during volume expansion diuresis. The metabolic characteristics of the papilla, when compared to cortex, also provide a basis for the observed differences in substrate selectivity of cortex and medulla with respect to utilization of glucose and lactate. The experimental approaches that may provide information bearing on the suggested mechanisms for regulation of papillary metabolism in relation to tubular work functions are indicated.

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