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H Wald

Publications and source records attributed to H Wald.

At least 73 records · Page 4Linked to original sources
PubMed1983

Renal effect of vitamin D metabolites: evidence for the essential role of the 25(OH) group.

The effects of 1 alpha (OH)vitamin D3 [1 alpha (OH)D3] and 24,25(OH)2vitamin D3 [24,25(OH)2D3] on the phosphaturic action of parathyroid hormone (PTH) were studied in two groups of parathyroidectomized (PTX) rats. In group 1, PTX PTH-infused rats received intravenous 1 alpha (OH)D3, and in group 2, PTX PTH-infused rats received intravenous 24,25(OH)2D3. PTX PTH-infused rats served as controls. The effects of both vitamin D metabolites on renal PTH-activated adenylate cyclase (AC) were studied in vitro. In group 1, PTH increased fractional excretion of phosphate (CP/CIn) from 0.045 +/- 0.012 (+/- SE) to 0.263 +/- 0.011 (P less than 0.005). 1 alpha (OH)D3 failed to influence this response. In group 2, PTH increased CP/CIn from 0.055 +/- 0.008 to 0.289 +/- 0.027 (P less than 0.005). 24,25(OH)2D3 reduced the PTH-induced rise in CP/CIn from 0.289 +/- 0.027 to 0.192 +/- 0.021 (P less than 0.01) and decreased the urinary excretion of adenosine 3',5'-cyclic monophosphate. In vitro, 24,25(OH)2D3 blunted the PTH-activated AC, whereas 1 alpha (OH)D3 had no effect. These results show that 24,25(OH)D3, similar to two other 25(OH) metabolites of vitamin D-25(OH)vitamin D3 and 1,25(OH)2vitamin D3-suppresses the phosphaturic action of PTH, whereas 1 alpha(OH)D3, which is devoid of a 25(OH) group, lacks this effect. This suggests that a 25(OH) group is a prerequisite for the antiphosphaturic effect of vitamin D, whereas the 1 alpha (OH) group is not essential for this action.

24,25-Dihydroxyvitamin D 3↗
PubMed1983

Effect of chronic salt loading on renal Na-K-ATPase activity in the rat.

The effect of chronic salt loading in rats fed regular chow diet on renal Na-K-ATPase was studied. The high salt intake was associated with increased filtered load of sodium (control: 126 +/- 3.9 mueq/min, salt loaded: 146 +/- 2.5, mueq/min, P less than 0.001), increased net reabsorption of sodium (control: 125.3 +/- 3.9 mueq/min, salt load: 134.8 +/- 2.4 mueq/min, P less than 0.05), increased urinary excretion of potassium (control: 2.4 +/- 0.09 mueq/min/min; salt loaded: 3.0 +/- 0.1 mueq/min, P less than 0.001) and increase in single kidney weight (control: 0.798 +/- 0.010 g, salt loaded: 0.937 +/- 0.015 g, P less than 0.001). The above mentioned changes were associated with significant increase in renal microsomal and whole homogenate medullary Na-K-ATPase activity in the salt loaded group (microsomes: control 74.1 +/- 4.9 mumole Pi/mg prot/hr, salt loaded 112.7 +/- 6.0 mumole Pi/mg prot/hr, P less than 0.001; whole homogenate: control 22.7 +/- 1.0 mumole Pi/mg prot/hr, salt load 29.4 +/- 1.6 mumole Pi/mg prot/hr, P less than 0.005), while cortical and papillary Na-K-ATPase activity remained unchanged. Taken together, these results show that increased filtered and reabsorbed load of sodium, which follows high salt intake, is associated with an increased renal Na-K-ATPase activity. The preferential rise in medullary enzymatic activity may be interpreted as suggesting that these changes may stem from increased delivery and reabsorption of sodium in the ascending limb of Henle's loop.

Adenosine Triphosphatases↗
PubMed1982

Renal function and Na-K-ATPase in rats after suprarenal ligation of inferior vena cava.

To assess the effects of altered renal function on Na-K-ATPase, the following groups of rats were studied: 1. rats with suprarenal vena cava ligation (SVCL), la. DOCA-treated rats with SVCL, 2. rats with infrarenal vena cava ligation (IVCL), 3. rats with glycerol-induced acute renal failure, 4. rats with bilateral ureteric ligation, and 5. K-exalate-treated rats with SVCL. In group 1, acute renal failure with hyperkalemia developed and medullary Na-K-ATPase increased from 95 +/- 5 in control to 155 +/- 7 mumol Pi/mg prot/h, P less than 0.001, DOCA did not prevent the increase of Na-K-ATPase. In group 2, medullary Na-K-ATPase decreased from 130 +/- 10 in control to 88 +/- 7, P less than 0.01, in rats with IVCL. In group 3, cortical Na-K-ATPase decreased from 55 +/- 5 to 27 +/- 6, P less than 0.02. In group 4, Na-K-ATPase was unchanged. In group 5, maintenance of normokalemia prevented the rise in Na-K-ATPase. These experiments demonstrated a K-dependent activation of medullary Na-K-ATPase after SVCL but not in other forms of renal failure. Because SVCL diminishes drastically GFR per nephron, the present findings imply that increased loads of Na and K per nephron are not a prerequisite for an increase in medullary Na-K-ATPase. Hyperkalemia in presence of increased renal venous pressure seems to be causally related to the rise in medullary Na-K-ATPase activity.

Adenosine Triphosphatases↗
PubMed1982

Glutamine uptake by rat renal basolateral membrane vesicles.

The presence of a sodium-dependent, saturable uptake process is described in basolateral membranes of rat renal cortex for L-glutamine. Concentration-dependence studies indicate the presence of multiple transport systems with Km1 of 0.032 mM and V1 of 0.028 nmol/mg of protein per min, and Km2 of 17.6 mM and V2 of 17.6 nmol/mg of protein per min. Lysine completely inhibits the high-affinity, low-capacity Km system and partially inhibits the low-affinity, high-capacity system. Cystine and other dibasic amino acids also affect glutamine uptake.

Amino Acids↗
PubMed1982

Homocystine uptake in isolated rat renal cortical tubules.

Isolated rat renal cortical tubules were used to study the nature of homocystine entry into the tubule cell and its transport interactions with cystine and the dibasic amino acids. The uptake of homocystine with time was progressive, reaching a steady state after 60 min. of incubation. Analysis of the intracellular pool after 5 and 30 min. of incubation revealed that virtually all of the transported homocystine had been converted to other metabolites of the transsulfuration pathway. The major metabolite was cystathionine with a somewhat lesser, but still significant amount as S-adenosylhomocysteine. A kinetic analysis showed that two systems for cellular entry of homocysteine existed with a Km1 of 0.17 mM and a Km2 of 7.65 mM. Arginine and lysine inhibited homocystine uptake via the low Km, high affinity system, but appeared not to inhibit the high Km, low affinity system. Cystine inhibited the low Km, high affinity system, but had an indeterminate effect on the high Km, low affinity system. Homocystine inhibited the uptake of cystine, lysine and arginine by isolated rat renal cortical tubules. The inhibition of homocystine on cystine uptake appeared to occur on both the high and low Km system for tubule cell entry of cystine. The data suggest that the low Km system for homocystine transport is shared with cystine and the dibasic amino acids. These data extend the knowledge of homocystine metabolism and provide a rational basis for new approaches to the treatment of homocystinuria.

Amino Acids↗
PubMed1981

Amino acid uptake by isolated renal brush border membrane vesicles in various buffers.

The uptake of amino acids by isolated rat renal brush border membrane vesicles in a modified Krebs-Ringer bicarbonate buffer and a phosphate buffer was compared to the uptake in the standard membrane vesicle buffer, Tris-Hepes-mannitol. The uptake in the modified Krebs-Ringer bicarbonate buffer was similar to that in the Tris-Hepes-mannitol buffer. Removal of the ionic constituents other than NaCl and NaHCO3 in the modified Krebs-Ringer bicarbonate buffer (KCl, CaCl2, KH2PO4 and MgSO4) did not affect the amino acid uptake by the isolated membrane vesicles. The timed uptake of proline under sodium gradient conditions in a phosphate buffer had a markedly dampened overshoot. Kinetic analysis of the initial rate of proline uptake in a phosphate buffer compared to a Tris-Herpes-mannitol buffer showed two entry systems for proline in each buffer with similar Km values, but the maximal rate of transport (V) for each system in the phosphate buffer was much lower than that in the Tris-Hepes-mannitol buffer. From these data, phosphate buffer does not appear to be a suitable medium for the study of amino acid uptake by isolated brush border membrane vesicles.

Amino Acids↗
PubMed1981

Evidence for interference of 25(OH)vitamin D3 with phosphaturic action of glucagon.

The effect of 25(OH)vitamin D3 [25(OH)D3] on the phosphaturic action of glucagon was studied using clearance techniques in the following groups of rats: group 1, parathyroidectomized (PTX) glucagon-infused rats receiving intravenous 25(OH)D3; group 2, PTX 25(OH)D3-pretreated rats receiving intravenous glucagon; and group 3, the thyroparathyroidectomized glucagon-infused rats receiving intravenous 25(OH)D3. The effect of 25(OH)D3 on glucagon-induced increase of cAMP in kidney slices and glucagon-activated adenylate cyclase (AC) in kidney membrane fractions was studied in vitro. In group 1, 25(OH)D3 suppressed the glucagon-induced phosphaturia by reducing fractional excretion of phosphorus (CP/CIn) from 0.175 +/- 0.02 (mean +/- SE) to 0.112 +/- 0.12 (P less than 0.05); this was associated with a reduction of urinary cAMP from 1,830 +/- 230 to 660 +/- 120 pmol/min (P less than 0.01). In group 2, pretreatment with 25(OH)D3 reduced CP/CIn from 0.221 +/- 0.025 to 0.108 +/- 0.012 (P less than 0.005). In group 3, 25(OH)D3 reduced CP/CIn from 0.165 +/- 0.012 to 0.075 +/- 0.011 (P less than 0.005). In vitro, 25(OH)D3 blunted the glucagon-induced activation of the AC/cAMP system by reducing AC from 570 +/- 30 to 325 +/- 28 pmol cAMP.mg protein-1.h-1 (P less than 0.01) and the cAMP level from 11.2 +/- 0.9 to 8.5 +/- 0.7 pmol cAMP/g wet tissue (P less than 0.05). These results show that 25(OH)D3 blunts the phosphaturic action of glucagon and suggest that this response may be mediated through suppression of the AC/cAMP system.

Animals↗
PubMed1977

Effect of salt loading in the rat on adenylate cyclase and phosphodiesterase activity in kidney cortex, medulla and papilla.

Adenylate cyclase (AC) and phosphodiesterase (PDE) activities were studied in the cortex, medulla and papilla of the rat kidney. Sodium loading in vivo for 14 days resulted in a decrease of AC activity in the cortex, a small increase in the medulla and a substantial increase of AC activity in the papilla. Sodium loading caused reciprocal effects on PDE activity: an increase in kidney cortex and a decrease in kidney papilla. Loading of glucose in vivo or chronic administration of antidiuretic hormone in vivo did not cause the changes in AC or PDE observed after sodium loading. The possible significance of these findings is discussed.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1977

Microsomal ATPase of kidney papilla: sensitivity to diuretics and other inhibitors.

Microsomal ATPase isolated from rat kidney papilla was compared to that from kidney medulla. Microsomal Na, K-ATPase from papilla was more sensitive to inhibition by ouabain, Cad N-ethyl-maleimide, Hg++, Thiomerin, ethacrynic acid and Furosemide than the enzyme from the medulla. Mg-ATPase of the papilla was less sensitive than the medullary enzyme to inhibition by Ca++, Cd++, N-ethyl-maleimide, Hg++, ethacrynic acid and Furosemide. Papillary Mg-ATPase was less sensitive than papillary Na, K-ATPase to all the inhibitors mentioned. Medullary Mg-ATPase was more sensitive than medullary Na, K-ATPase to inhibition by ethacrynic acid and Furosemide but less sensitive than medullary Na, K-ATPase to all the other inhibitors. Papillary Na, K-ATPase is the most sensitive to inhibition and papillary Mg-ATPase is the most resistant to inhibition by various diuretic drugs. The possible significance of these characteristics is discussed.

Adenosine Triphosphatases↗