Effect of osmolality on renal medullary Na-K-ATPase activity in the postobstructive kidney.

The aim of this study was to determine the effect of changes in osmolality on the reduced renal medullary Na-K-ATPase (EC 3.6.1.3) activity of the postobstructive kidney. The effect of osmolality on renal medullary Na-K-ATPase activity was studied by incubating tissue slices from sham-operated and bilaterally obstructed rats in media with osmolality varied before enzyme isolation using sodium chloride, choline chloride, or sucrose. Both sham-operated and bilaterally obstructed rat renal medullary enzyme showed a similar increase in activity with increased osmolality due to sodium chloride. Medullary Na-K-ATPase from the postobstructive kidney also showed increased activity with osmotic changes induced by choline chloride or sucrose. It is proposed that the decrease of Na-K-ATPase activity observed after bilateral ureteral obstruction is due, at least in part, to the loss of the solute concentration gradient in the kidney.     

Effect of fasting on Na-K-ATPase activity in rat small intestinal mucosa

The effect of fasting on mucosal Na-K-ATPase activity in various regions of rat small intestine was investigated. Fasting (17--48 h) was associated with a consistent decrease in specific and total activity of Na-K-ATPase in the jejunum, the levels tending to rise more distally. No effect on the specific activities of Mg-ATPase or alkaline phosphatase was found. Fasting was also associated with incresed adrenocortical activity and with decreases in mucosal mass, protein content, and histological dimensions of the jejunum, no similar changes being found in the distal small intestine. Glucose ingestion prevented the decrease in jejunal enzyme activity associated with fasting and elevated levels in the mid and terminal small intestine of fed animals. These effects suggest that Na-K-ATPase activity in small intestinal mucosa may be, in part, inducible.     

Failure of renal dopamine response to salt loading in chronic renal disease.

Eight patients with chronic glomerulonephritis and five age-matched normal volunteers were given additional sodium chloride by mouth under conditions of metabolic balance. Whereas in the normal volunteers plasma renin activity was suppressed and urinary excretion of free dopamine increased, in the patients dopamine was not mobilised and plasma renin activity was not completely suppressed. Abnormal retention of sodium and water in glomerulonephritis may be due partly to a failure to mobilise dopamine in the kidney. Specific renal dopamine agonists may be natriuretic and hypotensive in chronic glomerulonephritis.     

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.     

Effect of norepinephrine on renal tubular Na-K-ATPase and oxygen consumption

Previous studies from this laboratory have demonstrated that norepinephrine (NE) increases sodium dependent phenylalanine uptake by in vitro rat cortical tubules. In the present study, we have examined whether the observed increase in proximal tubular sodium transport, during NE treatment, is related to changes in membrane Na-K-ATPase and cellular oxygen consumption. Treatment of intact tubules with NE increased microsomal Na-K-ATPase activity but had no effect on cellular oxygen consumption or ouabain inhibitable oxygen consumption. The increased Na-K-ATPase activity is consistent with the observed increase in sodium transport while the lack of a detectable effect on oxygen consumption suggests that the increased transport does not require additional oxygen utilization.     

Effect of gangliosides on Na-K-ATPase activity and the conformation of microsomal membranes]

The effect of gangliosides on the activity of Na, K-ATPase and K-dependent nitrophenyl-phosphatase was studied. Low concentrations of gangliosides proved to activate Na, K-ATPase, and high ones to inhibit it. All the concentrations of gangliosides produced only an inhibitory effect on the K-dependent nitrophenyl-phosphatase. Inhibition of the enzyme by gangliosides is reversible and competitive in respect to K+. Calculation of Hill's coefficient demonstrated that both in case of the activating and of the inhibitory action gangliosides acted allosteric effectors. To ascertain the action mechanism of gangliosides on the enzyme their effect on the microsomal membranes was studied by the fluorescent probe method. Gangliosides were found to produce marked conformation shifts in the membranes of the brain microsomes.     

Calcium loading and renal function in trained subjects during restriction of muscular activity and chronic hyperhydration

It was suggested that negative calcium balance is not based on the shortage of calcium in the diet, but on the decreased tissular capacity of the body to retain calcium during hypokinesia (decreased muscular activity), and that chronic hyperhydration may be used to normalize calcium balance. To evaluate this hypothesis studies were performed on 30 long distance runners aged 23–26 yr, with an average maximum oxygen uptake 65 mL/kg/min during 364 d of hypokinesia (HK). All volunteers were divided into three equal groups: Ten volunteers were placed continuously under an average of 14.9 km/d (control subjects), ten volunteers were subjected continuously to HK (hypokinetic subjects), and ten volunteers were submitted continuously to HK with daily consumption of an additional amount of 26 mL water/kg body wt and 0.16 g sodium chloride (NaCl)/kg body wt (hyperhydrated subjects). For the simulation of the hypokinetic effect, the hypokinetic and hyperhydrated volunteers were kept under an average of 2.7 km/day for 364 d. During the prehypokinetic period and hypokinetic period calcium lactate loading tests (0.55 mEq/kg body wt) were performed. Urinary and blood electrolytes (sodium, ionized calcium, total calcium, magnesium, and phosphate) and blood parathyroid hormone (PTH) were determined. Urinary electrolytes and concentrations in blood thereof decreased in the hyperhydrated and increased significantly in the hypokinetic volunteers. Blood parathyroid hormone content increased in the hyperhydrated and decreased in the hypokinetic volunteers. After calcium lactate loading tests, the hypokinetic volunteers displayed a faster excretion of calcium and a decreased blood PTH content as compared to the control and hyperhydrated groups of volunteers. It was concluded that calcium deficiency during HK is associated with decreased tissular capacity of the body to retain calcium, whereas chronic hyperhydration may be used to prevent calcium deficiency in endurance trained volunteers during prolonged restriction of muscular activity.     

Effect of salt loading on the body water compartments in rats of different ages

In acute experiments on anaesthetized rats from three age groups (15-20, 25-30 days of postnatal life, adult ones), studies have been made on water basins of the organism after peroral injection of hypertonic (2.5-5%) solutions of NaCl (5 and 10 ml per 100 g of the body weight). It was demonstrated that during ontogenesis, total content of water decreases mainly at the expense of extracellular fluid. Infusion of saline solutions into the stomach of rats decreases fluid content in all water basins, especially in the interstitial one. The level of changes depends on the volume of the injected solution and, to a greater extent, on the concentration of the latter and the age of animals. The described response is due to osmotic transport of water into the alimentary tract, as suggested by the decrease of water content in this tract. The role of the digestive tract in osmotic and volume regulation during peroral salt loading is discussed.     

Effect of acute and chronic renal denervation on renal function after release of unilateral ureteral obstruction in the rat.

The role of the renal nerves in determining renal function after relief of 24-h unilateral ureteral obstruction (UUO) was studied using clearance techniques in anaesthetized rats. Acute renal denervation during the first 1--2 h after relief of UUO resulted in a significant increase in glomerular filtration rate (GFR), renal plasma flow (RPF), urine flow, and sodium and potassium excretion, changes which were not seen in the sham-denervated postobstructive kidney. Acute denervation of sham-operated normal kidneys caused a similar natriuresis and diuresis but with no change in GFR or RPF. Chronic renal denervation 4--5 days before UUO denervated postobstructive controls, while chronic denervation alone was associated with a significantly higher urine flow and sodium excretion rate from the denervated kidney. The effectiveness of renal denervation was confirmed by demonstrating marked depletion of tissue catecholamines in the denervated kidney. It was concluded that renal nerve activity plays a significant but not a major role in the functional changes present after relief of UUO. Chronic renal denervation did not protect against the functional effects of unilateral ureteral obstruction.     

Sodium excretion rates and renal responses to acute salt loading in the European starling

Summary Renal clearance studies were performed in European starlings (Sturnus vulgaris) in order to determine the extent of ureteral sodium excretion under control conditions and during an acute, hyperosmotic salt stress. These experiments also estimated the contribution of the lower intestine (colon and cloaca) to postrenal solute reabsorption by making both cloacal and ureteral urine collections in the same birds. A comparison of ureteral vs cloacal excretion rates found significantly higher sodium (9.09±1.30 vs 1.03±0.38 Eq·kg^–1·min^–1) and chloride (4.15±0.56 vs 1.00±0.38 Eq·kg^–1·min^–1) excretion rates during the ureteral collections. Fractional excretion of sodium was also significantly higher during ureteral collections, but this value did not exceed 1% of the filtered sodium load during either collection series. Urine flow rate was significantly higher during cloacal collections, suggesting osmotic back-flux of water across the cloacal wall. Infusion of a 1M NaCl solution resulted in rapid increases in glomerular filtration rate (GFR), urine flow rate, and urine osmolality. Fractional sodium and water reabsorption decreased by 11% and 4%, respectively. Glomerular counts and size distribution profiles, measured by in vivo alcian blue labelling, provided no evidence for a reduction in the number of filtering glomeruli during hyperosmotic saline loading. We conclude that renal sodium excretion rates for the starling are similar to those seen in other avian species and in mammals. These studies also provide direct evidence for postrenal modification of urine in this species, even under conditions of continuous flow. Acute hyperosmotic salt stress can, under some conditions, cause increased rather than decreased GFR, indicating multiple regulatory pathways. Finally, there was no evidence in these studies for glomerular shutdown in response to salt loading.     

Effect of chronic ethanol consumption on basic carboxypeptidase activity in regions of the rat brain

It is discovered that chronic consumption of ethanol induced decrease of carboxypeptidase H activity in striatum by 27%; increase of carboxypeptidase M activity in hippocampus by 67% and decrease in cerebral hemispheres by 34%; phenylmethylsulfonyl fluoride-inhibited carboxypeptidase activity increase in hypothalamus by 141%, in striatum by 60% and in optic and lamina quadrigemina by 34%. The role of basic carboxypeptidases in mechanisms of ethanol influence on the peptidergic systems are discussed.     

Osmolality and volume factors in salt gland control of pekin ducks after adaptation to chronic salt loading

Summary Pekin ducks were adapted to permanent osmotic stress by rearing them on a NaCl solution of increasing concentration up to 2% as drinking water. Their salt and water balance was compared with that of non-adapted ducks maintained on tap water. Amounts and osmolalities of salt gland secretion and cloacal discharges, plasma osmolality and electrolytes were measured during stepwise osmotic loading by intravenous infusion of NaCl solution of about 740 mosm·kg^–1, at rates of 0.25, 0.45 and 0.65 ml·min^–1. Before loading, the plasma osmolality of the adapted ducks was about 22 mosm·kg^–1 higher than in non-adapted animals. The initial step of loading induced salt gland secretion in the adapted ducks after an average rise of plasma osmolality of 3.6 mosm·kg^–1 and in the non-adapted animals after a rise of 7.8 mosm·kg^–1. The method of osmotic loading enabled both groups of animals to balance their water input and output. However, only the adapted ducks were able to balance NaCl input and output, predominantly by salt gland secretion, thus maintaining a stable plasma osmolality. The nonadapted ducks retained 42% of the salt load which resulted in a rise of plasma osmolality of 49 mosm·kg^–1, more salt being excreted by the kidneys than by the salt glands.In the salt-adapted ducks, salt gland activity, plasma osmolality and Na⁺ concentration did not correlate during balanced states of salt input and output. The involvement of tonicity receptors in salt gland control was confirmed by the stimulating effects of various hypertonic solutions. On the other hand, continuous loading by a constant infusion of NaCl solution of 1,300 mosm·kg^–1 induced a steady salt gland secretion at a rising plasma osmolality and thus suggested that a volume factor is involved in salt gland control. Inhibition of salt gland activity by withdrawing blood and activation by blood infusion confirmed this assumption. While a direct cause and effect relationship between volume changes and salt gland secretion cannot be demonstrated, the results indicate that volume changes in one or more extracellular compartments do affect salt gland secretion.Supported by Deutsche Forschungsgemeinschaft (Si 320/2)     

Acetylcholinesterase activity in chronic renal failure

Twenty healthy subjects and 39 Chronic Renal Failure patients (CRF-patients) maintained on chronic hemodialysis were used in this investigation to study the changes in acetylcholinesterase (AChE) activity of red blood cells (RBCs). The CRF-patients were all undergoing hemodialysis treatment. AChE activity from the CRF-patients was determined before and after dialysis. An additional objective was to study the effect of chronic renal failure on human red blood cell aging. Blood samples were drawn from controls and CRF-patients in tubes containing EDTA or sodium heparin as an anticoagulant. Red blood cells were purified to avoid interference with monocytes, reticulocytes and leukocytes. The purified RBCs were subfractionated into young (y) (1.08-1.09), mid (m) (1.09-1.11) and old (o) (1.11-1.12) percoll density (g/mL) fractions using a discontinous percoll gradient. The mean +/- SD AChE per gram hemoglobin (U/g Hgb) activities in whole blood (WB), purified human red blood cells (PRBCs), young human red blood cells (y-RBCs), mid age human red blood cells (m-RBCs) and old human red blood cells (o-RBCs) in CRF-patients were 31.2+/-3.43, 29.3+/-3.26, 30.4+/-3.91, 25.1+/-5.25, 17.1+/-6.02 in females and 29.8+/-5.39, 28.8+/-5.29, 28.7+/-5.29, 23.7+/-5.39 and 16.0+/-5.60 in males. AChE activity from CRF-patients were higher than that found in the control subjects. The aging of human RBCs in both the controls and CRF-patients showed a progressive reduction in AChE activity. AChE activity of RBCs from female CRF-patients were significantly higher (p < 0.05) than that of the female control subjects. The RBCs isolated from male CRF-patients showed a higher AChE activity than control males, but a significant difference was only observed with the mid-age-cells. These studies further indicate that AChE activity remained insignificantly different in the various density based age subfractions of RBCs of both CRF-patients and controls.     

Effect of chronic resistive loading on inspiratory muscles in rats

The development of animal models of respiratory muscle training would be useful in studying the physiological effects of training. Hence, we studied the effects of chronic resistive loading (CRL) for 5 wk on mass, composition, and mechanics of inspiratory muscles in laboratory rats. CRL was produced by means of a tracheal cannula (loaded animals) and results were compared with sham-operated controls. Acutely, upper airway obstruction led to a doubling of inspiratory pleural pressure excursion and 25% decrease in respiratory rate. We observed no changes in lung pressure-volume curves, nor in the geometry of the respiratory system in loaded compared with control animals. Muscle mass normalized for body mass increased in the diaphragm (DI) and the wet weight-to-dry weight ratio increased in the sternomastoid (SM) in loaded compared with control animals. Loaded animals demonstrated a decrease in ether extractable (fat) content of the DI and SM muscles but not the gastrocnemius. For the DI there was no change in length at which active tension was maximal (Lo), but there was an increase in maximum tension at lengths close to Lo in loaded compared with control rats. Endurance did not change, although twitch tensions remained higher in loaded compared with control rats. We conclude that 1) alteration of inspiratory muscle structure and function occurs in rats with CRL; 2) the DI and SM demonstrate different adaptive responses to CRL; and 3) although maximum tension increases, endurance does not.     

Effect of salt on the activity of Streptomyces prolyl aminopeptidase

A salt-tolerant prolyl aminopeptidase from Streptomyces aureofaciens TH-3 (TH-3PAP) was purified from a culture supernatant. The gene encoding TH-3PAP was cloned and sequenced. The primary structure of TH-3PAP showed 65% identity with that of PAP from Streptomyces lividans (SLPAP) and possessed a conserved catalytic motif, GxSxGG, which is conserved in the alpha/beta hydrolase fold family. The characterization of the recombinants TH-3PAP and SLPAP indicated a difference: in 4.0 M NaCl, TH-3PAP showed enzyme activity, whereas SLPAP was inactive. Next, we constructed chimeras between TH-3PAP and SLPAP using an in vivo DNA shuffling system and a sandwich chimera (sc-PAP), whose region from 63 to 78 amino acids of TH-3PAP was substituted with that of SLPAP. Comparison of the biochemical properties between TH-3PAP and the salt-sensitive sc-PAP suggested that the fine tuning of the N-terminal conformation of TH-3PAP by hydrophobic interaction is important for the salt tolerance mechanism of the enzyme.     

Effect of salt stress on the respiratory activity ofAspergillus sydowii

Respirometric studies with mitochondrial, fractions and whole cells revealed the presence of a more actively functioning respiratory system inAspergillus sydowii grown under salinity conditions. Oxidation of substrate, i.e., succinate, by the mitochondrial fraction was inhibited by the addition of rotenone, antimycin A, and cyanide. Electron microscopic observations ofAsp. sydowii grown in the presence of 2M NaCl indicated a comparatively larger size of mitochondria than in the control grown culture. A relatively larger fraction of the total cytoplasmic volume was occupied by the mitochondria in theAsp. sydowii grown in the media containing 2M NaCl. Levels of respiratory enzymes like succinate dehydrogenase. NADH dehydrogenase, cytochrome oxidase, NADH oxidase, and succinoxidase were higher in the culture grown in the presence of 2 M NaCl than in that grown in the absence of NaCl.