Acid excretion by bicarbonate-free perfused rat kidney

1981 ◽  
Vol 240 (4) ◽  
pp. F306-F310
Author(s):  
M. H. Garvey ◽  
D. L. Maude
Keyword(s):  
Carbonic Anhydrase ◽  
Rat Kidney ◽  
Acid Excretion ◽  
Total Acid ◽  
Urine Ph ◽  
Titratable Acid ◽  
Perfused Rat Kidney ◽  
Reduced Rate ◽  
Isolated Rat

We measured titratable acid (TA) and NH4 excretion by isolated rat kidneys perfused either with conventional bicarbonate-containing solutions or with solutions in which bicarbonate was replaced by propionate. Rates of TA excretion by bicarbonate-perfused kidneys were similar to in vivo values, 0.27 +/- 0.04 mueq.ml GF-1 (0.21 mueq.min-1.g-1), and increased significantly under bicarbonate-free conditions to 0.70 +/- 0.12 mueq.ml GF-1 (0.42 mueq.min-1.g-1). At the same time the perfusate/urine pH difference (delta pH) increased significantly, from 0.63 +/- 0.06 to 0.92 +/- 0.06. Carbonic anhydrase inhibition by 5 X 10(-4) M acetazolamide alkalinized the urine of bicarbonate-perfused kidneys, while in the bicarbonate-free preparation the urine remained acid (delta pH = 0.27 +/- 0.04) and titratable acid continued to be excreted, though at a reduced rate, 0.19 +/- 0.04 mueq.ml GF-1. Under these same bicarbonate-free carbonic anhydrase-inhibited conditions, lowering the perfusate pH from 7.4 to 7.1 increased delta pH to 0.36 +/- 0.02 and caused total acid excretion (TA + NH4) to rise from 0.29 +/- 0.04 to 0.45 +/- 0.06 mueq.ml GF-1, and increasing the perfusate [HPO4] from 2.4 to 9.6 mM increased TA to 0.80 +/- 0.09 mueq.ml GF-1.

Dissociation of CO2 hydration and renal acid secretion in the dogfish, Squalus acanthias

1986 ◽  
Vol 250 (2) ◽  
pp. F288-F293 ◽  
Author(s):  
E. R. Swenson ◽  
T. H. Maren
Keyword(s):  
Carbonic Anhydrase ◽  
Acid Secretion ◽  
Hydrogen Ion ◽  
Phenol Red ◽  
Urine Ph ◽  
Urinary Ph ◽  
Bicarbonate Reabsorption ◽  
Acid Urine ◽  
Titratable Acid

Maximal rates of renal hydrogen ion secretion and bicarbonate reabsorption in the dogfish were stimulated by intravascular infusion of acidic and basic buffers: bicarbonate, phosphate, phenol red, dimethadione (DMO), imidazole, and piperazine-N,N'-bis(2 ethanesulfonic acid) (PIPES). There was no difference in titratable acid secretion or urinary pH after bicarbonate infusion despite a sevenfold increase in plasma bicarbonate. Bicarbonate reabsorption was increased 12-fold and showed no evidence of reaching a maximum. This was not altered by methazolamide, as expected, since there is no renal carbonic anhydrase in seagoing fish. Imidazole resulted in the greatest augmentation of renal titratable acid secretion (33----390 mueq . h-1 . kg-1) and did not alter urinary pH. Inhibition of organic base secretion by Darstine had no effect on the imidazole-induced maximal rate of acid secretion. This rate was compared with that of hydrogen ion generation calculated from the uncatalyzed reactions of CO2 and H2O or OH-, maximizing PCO2 and OH- gradients and reaction volumes in vivo. These calculated chemical rates could only account for 9-14% of the measured maximal acidification rate. Thus the powerful process that maintains constant acid urine pH is not only independent of carbonic anhydrase but can function well in a low CO2 environment in which the reactions CO2 + H2O or CO2 + OH- do not furnish enough protons for H+ secretion or HCO3- reabsorption. We conclude that following the cellular protolysis of water, processes other than those involving CO2 buffering of OH- permit H+ to engage in the formation of urine.

scholarly journals Metabolism of glycine- and hydroxyproline-containing peptides by the isolated perfused rat kidney

1985 ◽  
Vol 229 (2) ◽  
pp. 545-549 ◽  
Author(s):  
M Lowry ◽  
D E Hall ◽  
J T Brosnan
Keyword(s):  
Amino Acids ◽  
Rat Kidney ◽  
Isolated Perfused Rat Kidney ◽  
Perfused Rat Kidney ◽  
Rat Kidneys

Isolated perfused rat kidneys removed considerable quantities of glycyltyrosine, glycylhydroxyproline, tetraglycine and prolylhydroxyproline from the perfusate. The component amino acids are released into the perfusate and, in the case of the glycine-containing peptides, there is increased synthesis of serine. Removal of peptides was more than could be accounted for on the basis of filtration, so antiluminal metabolism is indicated. Metabolism of such peptides by the kidney may contribute to renal serine synthesis in vivo.

Effects of Prolonged Administration of Diamox on Excretion of Acid and Carbonic Anhydrase and Glutaminase Activities in the Kidney

1957 ◽  
Vol 189 (3) ◽  
pp. 551-556 ◽  
Author(s):  
Donald W. Seldin ◽  
Floyd C. Rector ◽  
H. C. Teng
Keyword(s):  
Carbonic Anhydrase ◽  
Enzyme System ◽  
Chronic Administration ◽  
Carbonic Anhydrase Activity ◽  
Prolonged Administration ◽  
Urine Ph ◽  
Alkaline Urine ◽  
Titratable Acid ◽  
Load Effects ◽  
Renal Carbonic Anhydrase

Diamox inhibits renal carbonic anhydrase activity as effectively when given chronically as when given acutely. The persistently high urine ph, low titratable acid and high bicarbonate excretion in the urine of rats receiving Diamox chronically were the result of the alkaline load effects of sodium Diamox, rather than effects from the inhibition of carbonic anhydrase. The chronic administration of Diamox activated the renal glutaminase enzyme system, resulting in the excretion of normal or increased amounts of ammonia into an alkaline urine. The activation of glutaminase was potentiated by the restriction of dietary NaCl. An unexplained hypernatremia developed during the course of prolonged administration of Diamox.

Reversal of renal and smooth muscle actions of the thromboxane mimetic U-44069 by diltiazem

1986 ◽  
Vol 250 (4) ◽  
pp. F619-F626 ◽  
Author(s):  
R. Loutzenhiser ◽  
M. Epstein ◽  
C. Horton ◽  
P. Sonke
Keyword(s):  
Smooth Muscle ◽  
Rat Kidney ◽  
Tension Development ◽  
45Ca Uptake ◽  
Aortic Smooth Muscle ◽  
Control Value ◽  
Potent Vasoconstrictor ◽  
Isolated Rat

U-44069 is a stable prostaglandin (PG) H2 analogue and a potent vasoconstrictor. Its in vivo and in vitro actions mimic those of thromboxane A2. We have studied the effects of the calcium antagonist diltiazem upon the vasoconstriction induced by U-44069 using isolated rat aortic smooth muscle and isolated perfused rat kidney (IPRK). The administration of 10(-6)M U-44069 elicited maximally effective contractions in isolated aortic rings and increased 45Ca uptake from a control value of 285 +/- 6 mumol/kg to 344 +/- 8 mumol/kg. Diltiazem reduced U-44069-induced tension development and 45Ca uptake of isolated aortic smooth muscle 73 +/- 2 and 91 +/- 3%, respectively. The dose dependency of each of these effects of diltiazem was similar (EC50 = 369 nM and 334 nM for tension and 45Ca flux, respectively). When administered to the IPRK, 10(-6) M U-44069 caused a 82 +/- 3% decrease in glomerular filtration rate (GFR) and a 80 +/- 4% decrease in filtration fraction but reduced renal perfusate flow (RPF) only 13 +/- 8% (P less than 0.005). Diltiazem completely reversed the actions of U-44069 on the IPRK (EC50 = 288 nM and 323 nM for GFR and RPF, respectively). Diltiazem thus inhibited U-44069-induced tension development and 45Ca uptake by vascular smooth muscle and increased GFR within identical dose ranges. The contractile response of isolated rat glomeruli was also assessed. U-44069 reduced the volume of isolated glomeruli, but this action was neither prevented nor reversed by diltiazem. These results are consistent with the hypothesis that diltiazem increased GFR by inhibiting U-44069-induced Ca influx at preglomerular vessels.

Renal sulfate secretion is carbonic anhydrase dependent in a marine teleost, Pleuronectes americanus

1999 ◽  
Vol 276 (2) ◽  
pp. F288-F294 ◽  
Author(s):  
J. Larry Renfro ◽  
Thomas H. Maren ◽  
Cristina Zeien ◽  
Erik R. Swenson
Keyword(s):  
Carbonic Anhydrase ◽  
Pleuronectes Americanus ◽  
Marine Teleost ◽  
Sulfate Transport ◽  
Urine Ph ◽  
Primary Monolayer ◽  
Almost All ◽  
Primary Monolayer Cultures

Though chemical assays indicate that carbonic anhydrase (CA) activity is present in marine teleost nephrons, CA inhibitors have no effect on urine pH or bicarbonate excretion, parameters typically CA dependent in almost all vertebrate groups. Because marine teleost renal sulfate secretion is associated with bicarbonate anion exchange, we investigated the effect of CA inhibition on transepithelial sulfate transport by flounder renal tubule primary monolayer cultures (PTC) and on renal sulfate secretion (Q˙so 4) by intact flounder. Both methazolamide and ethoxzolamide (10 μM) inhibited PTC secretory flux by ∼50%; reabsorptive sulfate flux, Na-dependent glucose transport, and transepithelial electrical resistance were unaffected. A CA inhibitor restricted to the extracellular space (10 μM polyoxyethylene-aminobenzolamide, 3.7 kDa) had no effect on PTC sulfate transport. Intravenous administration of methazolamide reducedQ˙so 4almost 40% and had no effect on glomerular filtration rate (GFR), urine flow rate, or Pi excretion rate. Serum pH was significantly reduced 0.2 units, whereas urine pH was unchanged. Together, the in vitro and in vivo results indicate that CA facilitates renal sulfate secretion in the seawater teleost.

Transamination of branched-chain keto acids by isolated perfused rat kidney.

1978 ◽  
Vol 235 (1) ◽  
pp. E47
Author(s):  
W E Mitch ◽  
W Chan
Keyword(s):  
Amino Acids ◽  
Rat Kidney ◽  
Branched Chain Amino Acids ◽  
Keto Acid ◽  
Branched Chain Amino Acid ◽  
Keto Acids ◽  
Perfused Rat Kidney ◽  
Branched Chain ◽  
Branched Chain Keto Acids ◽  
Isolated Rat

Isolated rat kidney perfused without substrate released serine, glycine, and taurine, and substantially smaller amounts of other amino acids. When branched-chain keto acids were added, the corresponding amino acids were released at rates amounting to 15-25% of keto acid disappearance. Perfusion with 2 mM alpha-keto-isovalerate or alpha-keto-beta-methylvalerate caused an increased glucose release amounting to 18-23% of keto acid disappearance. The activity of branched-chain amino acid transferase (BATase) was significantly stimulated by perfusion with the analogue of leucine, but not by perfusion with alpha-ketoglutarate, the analogues of valine or isoleucine, or with leucine itself. These findings document that the kidney converts branched-chain keto acids in part to the corresponding amino acids and suggest that the keto analogue of leucine may be involved in the control of renal BATase activity, thereby indirectly regulating the metabolism of branched-chain amino acids.

Functional evaluation of isolated perfused rat kidney

1963 ◽  
Vol 18 (6) ◽  
pp. 1239-1246 ◽  
Author(s):  
Arthur W. Bauman ◽  
Thomas W. Clarkson ◽  
Ellen M. Miles
Keyword(s):  
Rat Kidney ◽  
Tubular Secretion ◽  
Functional Evaluation ◽  
Normal Limits ◽  
Glucose Reabsorption ◽  
Potassium Lactate ◽  
Perfused Rat Kidney ◽  
Filtered Load ◽  
Tubular Dilatation

A technique for perfusing the isolated rat kidney with heparinized whole blood is described. Numerous aspects of renal function are evaluated. Blood and urine flows approximated normal limits occasionally but diminished and increased, respectively, with time. The reabsorption rates of osmoles, sodium, chloride, potassium, lactate, and phosphate were proportional to the filtered loads. Variations in filtered load were due mainly to changes in glomerular filtration rate (GFR). Tubular secretion of p-amino hippuric acid varied with the GFR, and TmPAH per milliliter GFR was 60% of in vivo values. Glucose reabsorption was practically complete. Urine osmolalities, initially in the range 400–1,000 mosmoles/liter, fell during a perfusion, often to values well below plasma levels. Postperfusion histologic studies usually showed slight to moderate tubular dilatation. It was concluded that: 1) The handling of individual ions approximated in vivo function. 2) Changes in GFR and in the rate of excretion of PAH represented changes in the number of active nephrons. 3) Low urine osmolalities were due to decreasing ability of the nephrons to reabsorb water. blood and urine flow; electrolyte excretion Submitted on February 25, 1963

Nitric oxide enhancement of erythropoietin production in the isolated perfused rat kidney

1995 ◽  
Vol 269 (4) ◽  
pp. C917-C922 ◽  
Author(s):  
K. Yoshioka ◽  
J. W. Fisher
Keyword(s):  
Nitric Oxide ◽  
Rat Kidney ◽  
Mrna Levels ◽  
Isolated Perfused Rat Kidney ◽  
Intracellular Cgmp ◽  
Perfused Rat Kidney ◽  
Arterial Po2

We have previously reported that nitric oxide (NO) and guanosine 3',5'-cyclic monophosphate (cGMP) may be involved in the regulation of erythropoietin (Epo) production in response to hypoxia both in vivo and in vitro (20). In the present studies, we have used the isolated perfused rat kidney to assess the role of NO in oxygen sensing and Epo production. When arterial PO2 was reduced from 100 mmHg (normoxemic) to 30 mmHg (hypoxemic) in the perfusate of this system, perfusate levels of Epo were significantly increased. This hypoxia-induced increase in Epo production was significantly decreased by the addition of NG-nitro-L-arginine methyl ester (L-NAME; 1 mM) to the perfusates. Hypoxemic perfusion also produced a significant increase, and L-NAME significantly inhibited this increase, in intracellular cGMP levels in the kidney when compared with normoxemic perfused kidneys. Quantitative reverse transcription-polymerase chain reaction also revealed that hypoxemic perfusion produced significant increases in Epo mRNA levels in the kidney, which was blocked by L-NAME. Our findings further support an important role for the NO/cGMP system in hypoxic regulation of Epo production.

Effects of atrial natriuretic peptides on metabolism of arginine vasopressin by isolated perfused rat kidney

1992 ◽  
Vol 263 (2) ◽  
pp. R273-R278
Author(s):  
M. R. Lebowitz ◽  
A. M. Moses ◽  
S. J. Scheinman
Keyword(s):  
Arginine Vasopressin ◽  
Rat Kidney ◽  
Fractional Excretion ◽  
Metabolic Clearance ◽  
Isolated Perfused Rat Kidney ◽  
Perfused Rat Kidney ◽  
Clearance Receptor ◽  
Atrial Natriuretic

Atrial natriuretic peptide (ANP) antagonizes the release and action of arginine vasopressin (AVP) both in vivo and in vitro. We have reported that ANP increases the urinary and metabolic clearances of AVP in normal subjects (A. M. Moses et al. J. Clin. Endocrinol. Metab. 70: 222-229, 1990). To clarify this effect, we perfused isolated rat kidneys in vitro and measured the clearances of AVP for 30 min after the addition of rat ANP [rANP-(1-28), 10(-7) M]. In the perfused kidney, rANP increased the urinary clearance of AVP (UCAVP) from 321 +/- 19 to 417 +/- 20 microliters/min (P less than 0.01) and increased the glomerular filtration rate (GFR) from 558 +/- 28 to 696 +/- 28 microliters/min (P less than 0.01). Fractional excretion of AVP was unchanged. Rates of AVP reabsorption were directly related to filtered AVP, and this relationship was not altered by ANP. ANP did not affect the total organ clearance or the renal metabolic clearance of AVP. The increase in GFR was associated with increases in renal vascular resistance (P less than 0.05), filtration fraction (P less than 0.01), and sodium excretion (P less than 0.001). UCAVP also increased when GFR was raised without ANP by perfusing at higher pressures. The rat ANP clearance receptor agonist [cANP- (4-23), 10(-7) M] did not change GFR or UCAVP. ANP increases UCAVP in the isolated perfused rat kidney. This appears to be a hemodynamic effect of ANP, acting through its biological receptor and not the clearance receptor.(ABSTRACT TRUNCATED AT 250 WORDS)

Cystine and lysine reabsorption in the isolated perfused rat kidney

1989 ◽  
Vol 256 (5) ◽  
pp. F901-F908
Author(s):  
K. A. Roby ◽  
S. Segal
Keyword(s):  
Transport System ◽  
Brush Border ◽  
Rat Kidney ◽  
Isolated Perfused Rat Kidney ◽  
Transport Studies ◽  
Perfused Rat Kidney ◽  
Renal Tubular Reabsorption ◽  
Renal Tubular

Renal tubular reabsorption of cystine and lysine were studied in the isolated perfused rat kidney to bridge the gap between in vivo clearance studies, and in vitro transport studies of tubule fragments, cells, and brush-border membranes. Lysine was reabsorped by a saturable transport system shared by the dibasics. Cystine was also reabsorbed by a saturable transport system, which was shared in part by the dibasics (maximum inhibition 30%). The lysine threshold (Fmin) was 0.9 mumol.min-1.g-1, with a tubular maximum (TM) of 2.4 mumol.min-1.g-1. The cystine Fmin was 0.06 mumol.min-1.g-1; the TM could not be estimated because it was above the limit of cystine solubility. There was no evidence of cystine ,secretion.- The gamma-glutamyltransferase inhibitor, AT-125, decreased cystine excretion, but only in the presence of glutathione, glycine, glutamate, and the diabasic amino acids. This suggests that cystine from glutathione degradation at the brush border may contribute to urinary cystine (an explanation of the phenomenon of cystine secretion), but only under certain conditions.

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