The effect of the anions, phosphate and sulphate, on normal rates of excretion of potassium in dogs.

Small doses of (NH4)2HPO4 or KH2PO4 by stomach tube caused increase in plasma PO4 and PO4 excretion. Above a threshold of 0-8 mmol. 1(-1), increase of plasma PO4 by 0-5 mmol. 1(-1) caused PO4 excretion to increase by about 35 mumol. min.-1 After KH2PO4 this relationship was not altered by the concurrent increases in plasma K and K excretion. After doses of (NH4)2SO4 or K2SO4, excretion of SO4 was similarly related to plasma SO4 and was independent of plasma K and K excretion. An effect of PO4 on K excretion was observed after doses of (NH4)2HPO4, when increased excretion of PO4 was accompanied by increased excretion of K without change in plasma K. There was also increased excretion of NH4 and a small increase in Na excretion. The changes were similar to those produced by (NH4)2SO4 [O'Connor and Summerill, 1976]. KH2PO4 and K2SO4 produced increase in plasma K and increased excretion of K not significantly different from the changes produced by KCl or KHCO3 [Baylis and O'Connor, 1976]. After KH2PO2 or K2SO4, the urinary anion was PO4 or SO4, instead of Cl and HCO3. Any effect of anions on K excretion was much less than the effect of increase in plasma K. At low rates of excretion of K, increased urinary excretion of impermeant anion can determine increased excretion of K. However, the effect of anion is small in comparison with the effect of increase in plasma K.     

Excretion of electrolytes, free cortisol and aldosterone-18-oxo-glucuronide in 24-hr urines of the Mongolian gerbil (Meriones unguiculatus): effect of lysine-vasopressin and adrenocorticotrophin administration, and of changes in sodium balance

1. Administration of lysine-vasopressin (LVP, 1 IU/animal) strongly reduced electrolyte excretion in 24 hr urines of adult male Mongolian gerbils, but had no effect on free cortisol (C) or aldosterone-18-oxo-glucuronide (Aldo-gluc.) excretion. 2. (1-24) ACTH, given at a dosage of 20 IU/animal, increased C and Aldo-gluc. excretion but did not influence electrolyte excretion. 3. Fluid intake and potassium excretion were decreased in animals offered a control or a sodium-deficient diet; contrasting, excretion of C was stimulated. 4. In contrast to other rodents, Aldo-gluc. excretion showed no changes in Mongolian gerbils offered a sodium-deficient diet, but was diminished in animals either fed a control diet or given saline (154 mmol/l) as drinking water.     

The effect of emersion and handling on the nitrogen excretion rates of Clarias gariepinus

African catfish Clarias gariepinus (=119.9&30.6 g) were exposed to periods of emersion (5, 30, 60, 90 and 180 min) and the ammonia and nitrogen excretion rates measured following re-immersion. Immediately following re-immersion (0–30 min), the ammonia excretion and relative ammonia excretion was greatest for the 5-min emersion gro up. Exposure to extended periods of emersion resulted in a decrease in total nitrogen excretion, notably ammonia excretion, although no significant changes were observed in the non-ammonia component of C. gariepinus .     

Role of the hepatocyte microtubular system in the excretion of bile salts and biliary lipid: implications for intracellular vesicular transport

The role of the hepatocyte microtubular system in the transport and excretion of bile salts and biliary lipid has not been defined. In this study the effects of microtubule inhibition on biliary excretion of micelle- and non-micelle-forming bile salts and associated lipid were examined in rats. Low-dose colchicine pretreatment had no effect on the baseline excretion of biliary bile salts and phospholipid in animals studied 1 hr after surgery (basal animals), but slightly retarded the excretion of tracer [14C]taurocholate relative to that of lumicolchicine-pretreated (control) rats. However, colchicine pretreatment resulted in a marked reduction in the excretion of 2 mumol/100 g doses of a series of four micelle-forming bile salts of differing hydrophilicity, but had no significant effect on the excretion of the non-micelle-forming bile salt, taurodehydrocholate. Continuous infusion of 0.2 mumol of taurocholate/(100 g.min) following 24 hr of biliary drainage (depleted/reinfused animals) resulted in physiologic bile flow with biliary excretion rates of bile salts, phospholipid, and cholesterol that were markedly inhibited (mean 33, 39, and 42%, respectively) by colchicine or vinblastine pretreatment. Excretion of tracer [14C]taurocholate also was markedly delayed by colchicine in these bile salt-depleted/reinfused animals. In contrast, colchicine did not inhibit bile salt excretion in response to reinfusion of taurodehydrocholate. Thus, under basal conditions, the microtubular system appears to play a minor role in hepatic transport and excretion of bile salts and biliary lipid. However, biliary excretion of micelle-forming bile salts and associated phospholipid and cholesterol becomes increasingly dependent on microtubular integrity as the transcellular flux and biliary excretion of bile salts increases, in both bile salt-depleted and basal animals. We postulate that cotransport of micelle-forming bile salts and lipids destined for biliary excretion, via an intracellular vesicular pathway, forms the basis for this microtubule dependence.     

The effect of gonadectomy and aromatase inhibition on the excretion of 19-nordeoxycorticosterone in rats

19-Nordeoxycorticosterone (19-norDOC) is a powerful mineralocorticoid, which has been postulated to be involved in the pathogenesis of some forms of hypertension. The urinary excretion of 19-norDOC by female rats is up to 20 times that of males. To demonstrate the influence of the gonads on the excretion of 19-norDOC, we measured the excretion of 19-norDOC in intact and gonadectomized male and female rats with and without replacement with testosterone (40 mg testosterone enanthate s.c.) or estrogen (4 mg estradiol valerate s.c.) and in intact animals receiving the aromatase inhibitor, 10-propargyl androstenedione (10-pA) (10 mg s.c.). Orchiectomy produced a significant increase in the urinary excretion of 19-norDOC in males. Testosterone treatment decreased 19-norDOC excretion by castrated males to below intact values, while estrogen administration increased its excretion. Oophorectomy had no consistent effect on 19-norDOC excretion. In oophorectomized females, testosterone administration significantly suppressed 19-norDOC excretion and estrogen replacement increased excretion slightly. 10-pA had little effect on the excretion of 19-norDOC in intact rats of either sex. In conclusion, it appears that 19-norDOC production is inhibited by testosterone, but is affected only slightly by estrogens.     

Effect of parathyroid extract on renal cyclic AMP excretion in patients with normocalciuric nephrolithiasis.

It is uncertain whether normocalcemic, normocalciuric patients with calcium nephrolithiasis have a disorder of calcium metabolism. We studied the effect of a parathyroid extract (PTE) INFUSION (1.4 U/kg body weight) on the urinary cyclic AMP excretion in 16 such patients. For comparison, we investigated groups of normal individuals and patients with primary hyperparathyroidism, renal insufficiency and different gastrointestinal diseases. The increase of cyclic AMP above basal excretion in patients with nephrolithiasis was only 1.2 +/- 0.3 mumol/h (mean +/- SEM), versus 2.5 +/- 0.5 mumol/h in normal subjects (p less than 0.05) although the basal excretion was similar. Patients with renal insufficiency had low basal excretion of cyclic AMP and little stimulation of excretion by PTH (increase, 0.3 +/- 0.06 mumol). Patients with primary hyperparathyroidism had high baseline cyclic AMP excretion but sub-normal stimulation by PTE (increase, 0.46 +/- 0.13); in contrast, patients with different gastrointestinal disease had high baseline excretion and supranormal stimulation of cyclic AMP excretion (increase, 5.2 +/- 0.6). We speculate that an impaired response to PTH might be involved in the slightly increased urinary calcium excretion in normocalcemic stone formers suggested by others.     

Effects of chitosan intake on fecal excretion of bisphenol A and di(2-ethyl)phthalate in rats

We evaluated the effects of chitosan intake on fecal excretion of bisphenol A (BPA) and di(2-ethyl)phthalate (DEHP) in rats. The rats were fed a chitosan diet (CHI group) or a control diet (control group) for 10 d and orally administrated BPA or DEHP (100, 500 mg/kg body weight, respectively) on day 4. Feces were collected and the rates of fecal excretion of BPA and DEHP were calculated. Fecal excretion rates of BPA and DEHP were significantly higher in the CHI group than in the control group. A significant negative correlation was observed between the fecal excretion rates of BPA and DEHP and apparent fat digestibility. Furthermore, the CHI group showed not only increased but also accelerated BPA excretion into the feces. In conclusion, we found that that chitosan intake significantly increased the fecal excretion of BPA, DEHP, and fat, suggesting that it might be useful for reducing adverse effects caused by lipophilic xenobiotics.     

Regional release of cyclooxygenase products after radiation exposure of the rat

The present study evaluated the regional release of cyclooxygenase products 4 h following 20 Gy gamma irradiation. Thoracic shielding reduced the radiation-induced increase in immunoreactive thromboxane B2 (iTxB2) excretion to control levels while abdominal shielding partially attenuated the altered excretion of this cyclooxygenase product. To assess the role the kidneys play in the radiation-induced increase in iTxB2 excretion, an in situ isolated perfused rat kidney model was developed. The excretion rate of iTxB2 from irradiated isolated perfused kidneys was not significantly different from sham-irradiated perfused kidneys. Radiation exposure did alter renal cyclooxygenase product release in that the excretion of immunoreactive prostaglandin E2 (iPG2) and immunoreactive 6-keto-PGF1 alpha was significantly increased (P less than 0.05) in irradiated isolated perfused kidneys. These data show that radiation-induced increases in iTxB2 excretion are primarily due to altered extrarenal synthesis and/or metabolism of this arachidonate metabolite.     

The influence of ration size and feeding frequency on ammonia excretion by juvenile Atlantic cod, Gadus morhua L.

Small groups of juvenile Atlantic cod, Gadus morhua L., were kept at 14°C in through-flow tanks and were fed known quantities of a compounded diet of natural food. The cod were fed single and multiple meals with ration size in the range 0.5 to 4.1% of total wet fish body weight. Ammonia production in each feeding experiment was monitored continuously.
For single-meal experiments, significant relationships were derived between ration size and (a) total ammonia excreted, (b) total exogenous ammonia excreted above endogenous excretion levels, (c) duration of the elevated phase of ammonia excretion, (d) maximum rate of ammonia excretion, and (e) time delay after feeding to reach maximum rate of ammonia excretion. Relationships between nitrogen loss as ammonia and nitrogen intake were examined and estimates of endogenous excretion rate and maintenance ration made.
Repetitive feeding resulted in cyclical variation in ammonia excretion. At the lowest ration size, ammonia excretion rates had nearly returned to the pre-feeding level within 24 h. At higher feeding levels, the effect of each successive meal tended to be cumulative, resulting in increasingly higher ammonia excretion rates which only stabilized towards the end of the experiments.     

Human parathyroid hormone (1-34) increases urinary excretion of lysosomal enzymes in rats

The kidney is the major target of parathyroid hormone (PTH), and PTH influences the urinary excretion of calcium, phosphate and hydrogen ions. It was previously reported that the urinary, excretion of N-acetyl-beta-D-glucosaminidase (NAG), a lysosomal enzyme, transiently increases after human PTH (hPTH) (1-34) infusion in normal subjects and idiopathic hypoparathyroidism patients, but not in pseudohypoparathyroidism type I patients. Here we report that intravenous infusion of hPTH(1-34) to rats transiently increased the urinary excretion of various lysosomal enzymes, such as beta-glucuronidase and acid phosphatase as well as NAG. However, it did not affect the urinary excretion of tubular brush border membrane enzymes, i.e. alkaline phosphatase, leucine aminopeptidase and gamma-glutamyl transpeptidase. Human PTH(1-34) dose-dependently increased the urinary excretion of NAG in rats with a peak at 30 min, which returned to a baseline within 60 min. The increase in the urinary NAG excretion caused by hPTH(1-34) positively correlated with the increase in the urinary cAMP excretion (r = 0.844, p < 0.01), and infusion of dibutyryl cAMP at a dose of 20 mg/kg similarly increased the urinary excretion of NAG. These results suggested that the increase in the urinary excretion of lysosomal enzymes caused by hPTH(1-34) may be a functional response to hPTH(1-34) occurring in the renal tubules via PTH signaling pathway.     

Stimulation of fecal fat excretion and the disposal of protoporphyrin in a murine model for erythropoietic protoporphyria

Erythropoietic protoporphyria (EPP) is characterized by toxic accumulation of the hydrophobic compound protoporphyrin (PP). Ferrochelatase-deficient (fch/fch) mice are an animal model for human EPP. Recently, we have demonstrated that the accumulation of another hydrophobic compound, unconjugated bilirubin, could effectively be treated by stimulation of fecal fat excretion. We investigated whether stimulation of fecal fat excretion enhanced the disposal of PP in fch/fch mice. Fch/fch mice were fed for 8 wk with a high-fat diet (16 wt% fat; control) or with the high-fat diet mixed with either a nonabsorbable fat (sucrose polyester) or the intestinal lipase inhibitor orlistat. The effects of the treatments on fecal excretion of fat and PP and on hepatic PP concentrations were compared with control diets. Fecal fat excretion in fch/fch mice on a high-fat diet was higher than in mice on a low-fat diet (+149%, P < 0.05). Sucrose polyesters and orlistat increased fecal fat excretion even more, up to sixfold of control values. However, none of the different treatments affected fecal PP excretion or hepatic PP concentration. Treatment of fch/fch mice with a high-fat diet, a nonabsorbable fat diet, or with orlistat increased the fecal excretion of fat but did not increase fecal PP excretion or decrease hepatic PP concentration. The present data indicate that accumulation of PP is not amenable to stimulation of fecal fat excretion.     

The possible role of endogenous digitalis-like substance in the regulation of circadian changes in urinary electrolyte excretion in man

The urinary volume (U.V.), Na excretion (UNaV) and K excretion (UKV) have been reported to show a circadian rhythm in man, but the mechanism of this rhythm has not been made clear. To investigate how atrial natriuretic peptide (ANP) and endogenous digitalis-like substance (DLS) participate in the circadian change in urinary electrolyte, the circadian changes in ANP and DLS (digoxin-like immunoactivity: DLI, Na-K-ATPase inhibitor: ATPI, ouabain binding inhibitor to Na-K-ATPase: OBI) were evaluated in 5 normal man. ANP, DLI and OBI showed no significant correlation with urinary electrolyte excretion, but there was a significant positive correlation between plasma ATPI and urinary Na excretion. From these results it is suggested that circulating Na-K-ATPase inhibitor (plasma ATPI) may be involved in the regulation of the circadian rhythm of urinary Na excretion.     

The measurement of leukotrienes in urine as diagnostic option in systemic mastocytosis

Clinical symptoms of patients with mastocytosis may include skin reactions, but also gastrointestinal symptoms with hyperacidity and dysmotility (e.g. ulcer, diarrhea, pain). They are mostly caused by mediators derived from activated mast cells. In order to investigate the impact of leukotrienes on the clinical symptoms excretion of leukotriene B4 (LTB4) and leukotrienes C4-D4-E4 (cysteinyl-leukotrienes) into urine was studied in 9 patients with indolent systemic mastocytosis divided into a group with high and low intensity of symptoms and in 11 healthy volunteers. Leukotriene excretion was determined by ELISA and correlated with methylhistamine excretion. Patients with systemic mastocytosis with high and low intense symptoms showed significantly higher urinary excretion of cysteinyl-leukotrienes than controls. There was a positive correlation of cysteinyl-leukotriene excretion and urinary methylhistamine excretion. LTB4 excretion was also significantly increased in patients with systemic mastocytosis compared to healthy volunteers. No correlation of urinary LTB4 excretion with urinary methylhistamine was observed. The present study demonstrates that urinary excretion of LTB4 and cysteinyl-leukotrienes LTC4-D4-E4 is clearly enhanced in indolent systemic mastocytosis Hence, determination of leukotriene excretion into urine can be used as a tool in the diagnostic and in the therapeutic monitoring of systemic mastocytosis.     

Urinary growth hormone excretion in 657 healthy children and adults: normal values, inter- and intraindividual variations.

Urinary growth hormone (u-GH) excretion was measured in 547 healthy children and 110 adults by ELISA with a detection limit of 1.1 ng/l u-GH after prior concentration of the urine samples (20- to 30-fold). u-GH excretion values were significantly dependent on the pubertal stage (p less than 0.0001) with maximum values in Tanner stage 3 for girls and 4 for boys. This corresponded to a peak in u-GH excretion between 11.5-14.5 years in girls and 12.5-16 years in boys. Additionally, u-GH excretion in adults was significantly higher than in prepubertal children (p less than 0.001). The day/night ratio of u-GH excretion (pg/h) was significantly higher in females than in males (p less than 0.01). In Tanner stages 1-4, u-GH excretion during the day was lower than that at night, whereas the opposite was true in late puberty and in adult women. The interindividual variation of u-GH excretion within the same Tanner stage was considerable and approximately double the intraindividual variation. The day-to-day variation could be further reduced by collection of three consecutive urine samples. The variations were larger if night samples instead of 24-hour samples were considered. The expression of u-GH excretion in nanograms per gram creatinine did not diminish the observed variation and blunted the pubertal increase in u-GH excretion. In conclusion, (1) u-GH excretion depends significantly on age, sex and pubertal maturation as does the day/night ratio of u-GH excretion. (2) The interindividual variation in u-GH excretion is considerable.(ABSTRACT TRUNCATED AT 250 WORDS)     

Urinary prostaglandin E excretion: Effect of chronic alterations in sodium intake and inhibition of prostaglandin synthesis in the rabbit

On the basis of acute experiments in animals, a role for prostaglandin E (PGE) in the regulation of urinary sodium excretion has been suggested. Limited information is available, however, concerning the possible role of PGE in chronic adjustments to sodium intake. These studies were designed to determine whether chronic changes in sodium balance would modify renal PGE excretion and whether partial inhibition of prostaglandin synthesis would after the ability of the kidney to adjust to an alteration in sodium intake. Thus, we measured sodium and PGE excretion in rabbits on chronic high and low salt diets before and after inhibition of prostaglandin synthesis with indomethacin or meclofenamate. Although the alterations in salt intake resulted in large changes in sodium excretion there was no significant change in urinary PGE excretion. After administration of either indomethacin or meclofenamate for several days there was a significant fall in PGE excretion, but no significant change in sodium excretion. These results suggest that in the rabbit 1) chronic changes in sodium excretion can occur without modifying PGE excretion (and presumably renal PGE synthesis) and 2) inhibition of PGE synthesis does not impair the kidney's ability to adjust to a chronic high or low sodium intake.     

The influence of endogenous mineralocorticoids on the composition of fetal urine

Experiments were carried out in 10 chronically catheterised fetal sheep aged 121-128 days. In 3 animals infusion of aldosterone (5 micrograms/h) caused a fall in fetal urinary Na/K ratio; an effect that was reversed by spironolactone 2.5 mg/kg followed by an infusion of 100 micrograms/h per kg. In 9 fetal sheep which had no previous treatment the same doses of spironolactone had no effect on fractional sodium excretion although the fractional excretion of potassium decreased (P less than 0.05) and the urinary sodium potassium (Na/K) ratio rose (P less than 0.05). Amiloride had a variable effect on sodium excretion but the fractional excretion of potassium decreased markedly (P less than 0.05). Thus in chronically catheterised fetal sheep, endogenous mineralocorticoid activity altered urinary potassium excretion and the urinary Na/K ratio. However this activity was low, as distal blockade with amiloride further decreased the fractional excretion of potassium and increased the urinary Na/K ratio.     

Increased excretion of bile acids by genetically hyperlipoproteinemic Zucker rat

Fecal excretion of neutral sterols and bile acids was measured in age-matched hyperlipoproteinemic Zucker obese rats and their lean litter mates. The bile acid excretion (mg/day ± SEM) in Zucker rats was significantly higher (p<0.01) when compared to lean controls (Zucker obese rats 41.68 ± 2.86; lean controls 29.85 ± 1.50). Neutral sterol excretion in both the groups of rats was similar. Total fecal steroid excretion (mg/day ± SEM) in Zucker rats was significantly higher (p<0.01) than in lean controls (Zucker obese rats 52.33 ± 3.50; lean controls 39.23 ± 2.16. The Zucker rat thus mimics the increased bile acid excretion noted previously in human Type IV hyperlipoproteinemia and could serve as an ideal animal model for studying the interrelationship between bile acid excretion and very low density lipoprotein metabolism.     

A metabolic theory of ecology applied to temperature and mass dependence of N and P excretion by common carp

Our study used a metabolic theory of ecology (MTE) to explore scaling of metabolic rates by body size and temperature, and to predict nutrient excretion by common carp (Cyprinus carpio). At high biomasses, common carp have negative impacts on water quality, and one mechanism is excretion of the nutrients N and P. We measured whole-body and mass-specific excretion rates during summer and winter for fish of different sizes (wet mass range 28–1,196 g) to produce an allometric scaling model capable of predicting excretion at different temperatures. We found positive relationships between both dissolved and total nutrient concentrations and fish wet mass in summer and winter, with greater excretion rates in summer (mean water temperature 24.2°C) than in winter (mean water temperature 9.2°C). Mass-specific excretion rates decreased with increasing fish size, consistent with the MTE, and the temperature-adjusted model explained more variation for N excretion than for P. The proportion of dissolved nutrients (NH₄ and PO₄) to total nutrients increased with increasing fish size. The significance of these models is that they can be used to predict population-based nutrient excretion by common carp when thermal history, fish density and size distribution in a water body are known.     

Factors influencing nitrogen and phosphorus excretion rates of fish in a shallow lake

Summary 1. Fish excretion can be an important source of nutrients in aquatic ecosystems. Nitrogen (N) and phosphorus (P) excretion rates are influenced by many factors, including fish diet, fish growth rate and fish size. However, the relative influence of these and other factors on community‐level excretion rates of fish is unknown. 2. We used bioenergetics modeling to estimate excretion rates of eight fish species in a shallow, Minnesota (U.S.A.) lake over four months in both 2004 and 2005. Excretion rates of each species were summed for community‐level N and P excretion rates, as well as the N : P ratio of excretion. We then used a model‐selection approach to assess ability of independent variables to predict excretion rates, and to identify the most parsimonious model for predicting N : P excretion ratios and P and N excretion rates at the community scale. Predictive models were comprised of the independent variables water temperature and average fish density, fish size, fish growth rate, nutrient content of fish and nutrient content of fish diets at the community scale. 3. Fish density and nutrient content of fish diets (either N or P) were the most parsimonious models for predicting both N and P excretion rates, and explained 96% and 92% of the variance in N and P excretion, respectively. Moreover, fish density and nutrient models had 1400‐fold more support for predicting N and 21‐fold more support for predicting P excretion relative to models based on fish density only. Water temperature, fish size, fish growth rates and nutrient content of fish showed little influence on excretion rates, and none of our independent variables showed a strong relationship with N : P ratios of excretion. 4. Past work has focused on the importance of fish density as a driver of fish excretion rates on a volumetric basis. However, our results indicate that volumetric excretion rates at the community scale will also change substantially in response to changes in relative abundance of fish prey or shifts in relative dominance of planktivores, benthivores, or piscivores. Changes in community‐scale excretion rates will have subsequent influences on algal abundance, water clarity, and other ecosystem characteristics.     

Effects of a chitosan intake on the fecal excretion of dioxins and fat in rats

We evaluated the effects of the intake of various dietary fibers on the fecal excretion of dioxins in rats. The rats were fed five types of dietary fiber diets, including a chitosan diet and control diet, for 20 d and then dioxins (120 ng/rat) were orally administered on day 15. The excretion of fecal dioxins was significantly higher in the chitosan group than in the control group, and dioxin excretion was positively correlated with fecal fat excretion. A comparison of the different types of chitosan showed that the efficacy of chitosan for fecal fat excretion was partly related to its viscosity. The chitosan intake promoted fecal dioxin excretion when the rats were exposed to highly toxic dioxins, and this excretion of fecal dioxins was related to the fecal fat excretion, suggesting that chitosan might be useful for reducing the adverse effects caused by lipophilic xenobiotics.