Atrial peptides inhibit oxygen consumption in kidney medullary collecting duct cells

1986 ◽  
Vol 251 (2) ◽  
pp. F379-F383 ◽  
Author(s):  
M. L. Zeidel ◽  
J. L. Seifter ◽  
S. Lear ◽  
B. M. Brenner ◽  
P. Silva
Keyword(s):  
Oxygen Consumption ◽  
Collecting Duct ◽  
Rabbit Kidney ◽  
Thick Ascending Limb ◽  
Direct Inhibition ◽  
Kidney Medulla ◽  
Inner Medullary Collecting Duct ◽  
Duct Cells ◽  
Collecting Duct Cells ◽  
Medullary Collecting Duct

Atrial natriuretic peptides (ANP) stimulate renal Na+ excretion by poorly understood mechanisms, perhaps involving direct inhibition of Na+ transport in the kidney medulla. To examine the effects of ANP on renal cells directly, we prepared highly purified cell suspensions derived from inner and outer medullary collecting duct and thick ascending limb of rabbit kidney and monitored ouabain-sensitive oxygen consumption (QO2). Human ANP diminished QO2 by 27.4 +/- 1.6% (mean +/- SE) in inner medullary collecting duct cells but had no effect in cells derived from outer medullary collecting duct or thick ascending limb. The inhibitory effect of ANP was not additive with either amiloride or ouabain. ANP was without effect in the presence of amphotericin. These results indicate that ANP inhibited Na+ entry in inner medullary collecting duct cells. ANP-mediated inhibition of QO2 was dose dependent (Ki = 5.5 X 10(-10) M) and exhibited selectivity for peptide structure. These results suggest that atrial peptides enhance renal sodium excretion partly by direct inhibition of medullary collecting duct sodium transport.

Response of rat inner medullary collecting duct to epidermal growth factor

1989 ◽  
Vol 256 (6) ◽  
pp. F1117-F1124 ◽  
Author(s):  
R. C. Harris
Keyword(s):  
Growth Factor ◽  
Binding Sites ◽  
Collecting Duct ◽  
Affinity Binding ◽  
Inner Medullary Collecting Duct ◽  
Duct Cells ◽  
Epidermal Growth ◽  
Collecting Duct Cells ◽  
Medullary Collecting Duct

Urine is an abundant source of epidermal growth factor (EGF) and prepro-EGF has been localized to the thick ascending limb and distal convoluted tubule of the kidney. However, the functional role of EGF in the kidney is poorly understood. Determination of EGF receptors and functional responses to EGF in intrarenal structures distal to the site of renal EGF production may prove critical to our understanding of the role of this peptide. These studies were designed to investigate the response to EGF of rat inner medullary collecting duct cells in culture and in freshly isolated suspensions. Primary cultures of inner medullary collecting duct cells demonstrated equilibrium binding of 125I-labeled EGF at 4 and 23 degrees C. At 23 degrees C, there was 89 +/- 1% specific binding (n = 30). Scatchard analysis of 125I-EGF binding suggested the presence of both high-affinity binding with a dissociation constant (Kd) of 5 X 10(-10) M and maximal binding sites (Ro) of 2.7 X 10(3) binding sites/cell and low-affinity binding, with Kd of 8.3 X 10(-9) M and Ro of 1.8 X 10(4) binding sites/cell. Bound EGF, 68 +/- 3%, was internalized by 45 min. EGF binding was not inhibited by antidiuretic hormone, atrial natriuretic peptide or bradykinin at 23 degrees C, but there was concentration-dependent inhibition of binding by transforming growth factor-alpha. Incubation with phorbol myristate acetate decreased 125I-EGF binding in a concentration-dependent manner. 125I-EGF binding was also demonstrated in freshly isolated suspensions of rat inner medullary collecting duct cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Heat stress protein-associated cytoprotection of inner medullary collecting duct cells from rat kidney

1993 ◽  
Vol 265 (3) ◽  
pp. F333-F341 ◽  
Author(s):  
S. C. Borkan ◽  
A. Emami ◽  
J. H. Schwartz
Keyword(s):  
Heat Stress ◽  
Thermal Injury ◽  
Collecting Duct ◽  
Rat Kidney ◽  
Metabolic Effects ◽  
Lactate Dehydrogenase Activity ◽  
Inner Medullary Collecting Duct ◽  
Duct Cells ◽  
Collecting Duct Cells ◽  
Medullary Collecting Duct

Although heat stress proteins (HSPs) mediate thermotolerance, the cellular targets of thermal injury and mechanisms of acquired cytoprotection are unknown. To describe the metabolic effects of hyperthermia and the potential mechanisms of thermotolerance, the following were measured in inner medullary collecting duct cells after a 43 degrees C and/or a 50 degrees C thermal insult: 1) state III mitochondrial respiration (SIII MR), 2) glycolytic rate, 3) lactate dehydrogenase activity, 4) membrane permeability, and 5) HSP 72 content. Compared with controls incubated at 37 degrees C, cells heated to 50 degrees C showed a 30 and 50% reduction in glycolysis and SIII MR, respectively. After heating to 50 degrees C, the cell membrane remained intact and immunoreactive HSP 72 was not detected. In contrast, heating to 43 degrees C induced accumulation of HSP 72 and transiently increased both SIII MR and glycolysis. In addition, prior exposure to 43 degrees C completely prevented the fall in SIII MR and glycolysis anticipated with a subsequent 50 degrees C insult. Cytoprotection gradually diminished over several days and correlated with the disappearance of HSP 72. Preservation of oxidative and anaerobic metabolism associated with HSPs may be important in developing resistance to thermal injury.

Functional upregulation of H+-ATPase by lethal acid stress in cultured inner medullary collecting duct cells

1997 ◽  
Vol 273 (4) ◽  
pp. C1194-C1205 ◽  
Author(s):  
Hassane Amlal ◽  
Zhaohui Wang ◽  
Manoocher Soleimani
Keyword(s):  
Collecting Duct ◽  
Acid Stress ◽  
Northern Hybridization ◽  
Mrna Levels ◽  
Inner Medullary Collecting Duct ◽  
Duct Cells ◽  
Acid Load ◽  
Collecting Duct Cells ◽  
Medullary Collecting Duct ◽  
Mutant Cells

The response of H+-ATPase to lethal acid stress is unknown. A mutant strain (called NHE2d) was derived from cultured inner medullary collecting duct cells (mIMCD-3 cells) following three cycles of lethal acid stress. Cells were grown to confluence on coverslips, loaded with 2′,7′-bis(carboxyethyl)-5(6)-carboxyfluorescein, and monitored for intracellular pH (pHi) recovery from an acid load. The rate of Na+-independent pHi recovery from an acid load in mutant cells was approximately fourfold higher than in parent cells ( P < 0.001). The Na+-independent H+ extrusion was ATP dependent and K+ independent and was completely inhibited in the presence of diethylstilbestrol, N, N′-dicyclohexylcarbodiimide, or N-ethylmaleimide. These results indicate that the Na+-independent H+ extrusion in cultured medullary cells is mediated via H+-ATPase and is upregulated in lethal acidosis. Northern hybridization experiments demonstrated that mRNA levels for the 16- and 31-kDa subunits of H+-ATPase remained unchanged in mutant cells compared with parent cells. We propose that lethal acid stress results in increased H+-ATPase activity in inner medullary collecting duct cells. Upregulation of H+-ATPase could play a protective role against cell death in severe intracellular acidosis.

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