Relation between renal and hepatic excretion of drugs: I. Phenol red in comparison with p-aminohippurate and indocyanine green

Preparation and properties of polyvinyl alcohol/chitosan-based hydrogel with dual pH/NH3 sensor for naked-eye monitoring of seafood freshness

To address the issue of food spoilage causing health and economic loss, we developed a pH/NH3 dual sensitive hydrogel based on polyvinyl alcohol/chitosan (PVA/CS) containing chitosan-phenol red (CP). The CP was synthesized via Mannich reaction and immobilized it in PVA/CS hydrogel through freezing/thawing method to prepare the final PVA/CS/CP hydrogel. The synthesis of CP was confirmed by 1H NMR, FT-IR, XRD, UV-vis, and XPS. The characteristics of hydrogel were evaluated by FT-IR, XRD, SEM, mechanical properties, thermal stability, leaching, and color stability tests. The PVA/CS/CP hydrogel showed distinctly different color at various pH and NH3 vapor levels (yellow to purple). The hydrogel exhibited obvious color changes (ΔE = 46.95) in response to shrimp spoilage, stored at 4 °C. It showed positive and strong correlation between the ΔE values of the indicator hydrogel and total volatile basic nitrogen (TVB-N) as (R2 = 0.9573) and with pH as (R2 = 0.8686), respectively. These results clearly show that the PVA/CS/CP hydrogel could be applied for naked-eye real-time monitoring of seafood freshness in intelligent packaging.

Does early infusion of red blood cells after trauma and hemorrhage improve organ functions?

OBJECTIVE

Early management of trauma victims includes control of bleeding and rapid restoration of intravascular volume. However, it remains controversial whether infusion of blood products is superior to crystalloids alone. Therefore, it was the aim of the present study to determine whether resuscitation with red blood cells plus lactated Ringer's solution (RL) is more effective than RL alone in improving the cardiovascular and hepatocellular functions after trauma and severe hemorrhage.

DESIGN

Prospective study.

SETTING

Laboratory.

SUBJECTS

Sprague-Dawley rats.

INTERVENTIONS AND MEASUREMENTS

Male adult rats were anesthetized and underwent a laparotomy to induce tissue trauma before hemorrhage. The animals were then bled to and maintained at a mean arterial pressure of 40 mm Hg until 40% of the maximal bleed-out (MB) volume was returned in the form of RL, and were then resuscitated with either four times the volume of MB with RL or washed red blood cells (RBC) (-45% the volume of MB) in three times the volume of RL over 60 mins. Various in vivo heart performance variables, cardiac output, and hepatocellular function (ie, the maximum velocity and the overall efficiency of indocyanine green clearance) were determined at 4 hrs after resuscitation. Hemoglobin, systemic oxygen delivery, circulating blood volume, and plasma levels of interleukin-6 were also measured.

MAIN RESULTS

At 4 hrs after RL resuscitation, heart performance, cardiac output and hepatocellular function were significantly depressed and plasma levels of interleukin-6 were significantly increased. Although infusion of RBC significantly increased mean arterial pressure, hemoglobin, and oxygen delivery compared with animals resuscitated with RL only, infusion of RBC did not further improve the depressed cardiovascular and hepatocellular functions under such conditions.

CONCLUSION

Because infusion of RBC and RL resuscitation do not improve organ functions compared with RL resuscitation without RBC, it appears that pharmacologic agents in addition to fluid resuscitation are needed to restore cardiovascular and hepatocellular functions after trauma and hemorrhage.

Renal handling of amino acids in 5/6-nephrectomized rats: stimulation of renal amino acid reabsorption after treatment with triiodothyronine or dexamethasone under amino acid load

In anaesthetized adult female rats, the renal amino acid handling was measured six days after 5/6 nephrectomy (5/6NX). The distinct rise in blood urea nitrogen as well as the significant reduction in urine flow and GFR indicate an impairment of kidney function. In principle, in 5/6NX rats amino acid plasma concentrations were comparable to those of control animals with two intact kidneys, whereas the fractional excretions (FEAA) of most endogenous amino acids measured were significantly enhanced. After bolus injection of leucine or taurine (each 20 mg/100 g b.wt.) or glutamine (90 mg/ 100 g b.wt.), dissolved in 2 ml normal saline per 100 g b.wt., the FEAA of both the amino acids administered and the endogenous amino acids increased as a sign of overloaded amino acid reabsorption capacity. This effect was more pronounced in 5/6NX rats than in controls. As early as one hour after amino acid load, plasma concentrations and FEAA returned to baseline values of 5/6NX rats. A pretreatment with triiodothyronine (20 micrograms/100 g b.wt.) or dexamethasone (60 micrograms/100 g b.wt.), both given intraperitoneally once daily for 3 days, stimulated the renal amino acid transport capacity in 5/6NX rats: the increase in FEAA after amino acid load was significantly lower compared to non-pretreated animals. This stimulation could be shown for the bolus amino acids and the endogenous amino acids and was more distinct in 5/6NX rats than in controls with two intact kidneys.

Epidermal growth factor (EGF) increases the renal amino acid transport capacity in amino acid loaded rats

In anaesthetized adult female rats, the influence of epidermal growth factor (EGF) on renal amino acid handling was investigated in glutamine, arginine (both 50 mg/100 g b.wt. per hour), or alanine (90 mg/100 g b.wt. per hour) loaded animals. Continuous infusions of the three amino acids were followed by an increase in the fractional excretion (FE) of the administered amino acids as well as of the other endogenous amino acids. Under load conditions (alanine, arginine or glutamine), EGF pretreatment (8 micrograms/100 g b.wt. subcutaneously for 8 days, twice daily 8 a.m. and 4 p.m.) was followed by a stimulation of renal amino acid reabsorption. The increase in the fractional excretion of the administered amino acids was significantly lower than in non-EGF-treated rats. These changes in amino acid transport were connected with a significant reduction of GFR after EGF pretreatment (0.96 +/- 0.10 vs. 0.62 +/- 0.07 ml/min x 100 g b.wt.) and a distinct increase in sodium excretion (2.98 +/- 0.55 vs. 4.97 +/- 0.71 muval/100 g b.wt. x 20 min). After loading with p-aminohippurate (PAH; 200 mg/100 g b.wt.), PAH excretion in EGF rats was increased by about 20%, whereas urinary protein excretion was lower in EGF pretreated rats (control: 0.45 +/- 0.04 vs. EGF: 0.18 +/- 0.03 mg/100 g b.wt. x 20 min). The PAH load reduced amino acid reabsorption as a sign of overloading of renal tubular transport capacity, but in EGF pretreated animals the amino acid excretion was only slightly increased under these conditions. Furthermore, EGF pretreatment depressed normal kidney weight gain significantly (874 +/- 18 vs. 775 +/- 32 mg/100 g b.wt.). EGF can improve the renal tubular transport capacity, but, compared to well-known stimulators of renal transport like dexamethasone or triiodothyronine, its effect is only of a moderate degree.

Renal amino acid transport in immature and adult rats during thallium-induced nephrotoxicity

The effect of Tl2SO4 (Tl, 2 mg/100 g b.wt.) on renal amino acid excretion and plasma amino acid composition was investigated in 10- and 55-day-old rats. Tl decreased glomerular filtration rate only in adult rats. On the other hand, the renal fractional excretion (FE) of amino acids was distinctly higher in adult rats as a sign of lower amino acid reabsorption capacity after Tl. In immature animals FE was increased only for a few amino acids. However, in both age groups Tl administration significantly decreased plasma amino acid concentrations, and was more pronounced in immature rats. The investigation of renal amino acid handling (1) confirms that Tl was more nephrotoxic in 55-day-old animals as demonstrated before using other parameters for nephrotoxicity testing and (2) showed that determination of renal amino acid handling is a suitable marker for nephrotoxicity in adult rats.

Functional and morphological aspects of thallium-induced nephrotoxicity in rats

Until now the effect of thallium (Tl) on renal function has not been investigated systematically. Therefore, the dose (5, 10, 15, 20 mg Tl2SO4/kg body wt., intraperitoneally) and time-dependence of renal damage was investigated in diuresis experiments on conscious rats. Morphology was evaluated after perfusion fixation in situ. Morphologic changes were localized in the thick ascending limb of the loop of Henle, mostly expressed at the 2nd day after Tl administration, which were completely normalized again at the 10th day. Other parameters such as Tl concentration, changes in water content and the activity of Na+/K(+)-ATPase as well as the diuretic effect of furosemide confirmed the Tl effect to be localized in the renal medulla. One single Tl administration is followed by a decrease in glomerular filtration rate (GFR) and urine volume and an increase of proteinuria. Electrolyte excretion was only slightly changed. All changes were reversible within the 10-day investigation period.

Effect of chronic administration of phenobarbital on the hepatobiliary transport of phenol red: assessment by statistical moment analysis

The effect of enzyme induction on the hepatobiliary transport of phenol red (PR) in rats was investigated by application of a new analytical system to determine local drug disposition based on statistical moment theory (T. Kakutani et al., J. Pharmacokin. Biopharm. 13:609-631, 1985). Employing the moment parameters obtained from the time courses of plasma and biliary concentrations of PR and its metabolite after intravenous injection, the hepatobiliary transport of PR was theoretically assessed by separating it into component subprocesses such as hepatic uptake, hepatobiliary transfer, and intrahepatic metabolism. The results demonstrated that the acceleration of plasma disappearance of PR caused by pretreatment with phenobarbital (PB), known to induce hepatic enzyme systems, could be attributed to elevation of both hepatic and extrahepatic clearances. While PB did cause bile flow elevation (choleresis) and increased metabolism, these effects were shown to make little contribution to accelerated plasma disappearance of PR, since it was shown that the hepatobiliary excretion of PR was rate-limited by the intrahepatic transfer process, which was unaffected by PB treatment. From the results of this study, this experimental/analysis methodology seems to be useful in obtaining detailed information about hepatobiliary transport of the drug from in vivo data.

Pharmacokinetics and excretion of phenol red in the channel catfish

1. Disposition of phenol red was examined in channel catfish (Ictalurus punctatus) after oral or intravascular (i.v.) dosing at 10 mg/kg body weight. 2. Phenol red was not detectable in plasma, urine, or bile after oral administration. 3. After i.v. dosing, plasma concentrations of phenol red were best described by a two-compartment pharmacokinetic model with distribution and elimination half-lives of 2.3 and 21 min, respectively. The apparent volume of distribution at steady state (Vss) was 225 ml/kg and total body clearance (Clb) was 658 ml/h per kg. Plasma protein binding was 19%. 4. Biliary excretion was the primary route of elimination of phenol red; in 24 h, 55% of the i.v. dose was excreted in bile compared with 24% in urine. No metabolites were detected in these fluids. 5. The use of anaesthesia during dosing had no effect on the quantitative excretion of phenol red by renal or biliary routes.

Relation between renal and hepatic excretion of drugs. XIV. Elimination of ioglycamic acid after nephrectomy, bile duct ligation, and after treatment with hormones or xenobiotics in young and adult rats

Ioglycamic acid (IGA) is effectively eliminated in young and adult rats via urine and bile. After administration of low doses hepatic excretion dominates whereas following high supply renal elimination surpasses biliary excretion. Hepatic transport of IGA is active, indicated by the occurrence of a transport maximum in vivo and by a distinct accumulation of this drug within liver slices in vitro. Renal removal of IGA is preferentially caused by glomerular filtration. A tubular reabsorption obviously does not occur because forced diuresis (mannitol, furosemide) does not increase renal excretion of this substance. As calculated from our clearance data and as a result of accumulation experiments in vitro on renal cortical slices the active tubular secretion of this organic anion can be excluded. In principle there are no qualitative changes in IGA elimination between the 20th and 55th day of life, but active hepatic transport of the drug is significantly lower in young, immature rats. After bile duct ligation, renal excretion of IGA increases distinctly in both age groups, whereas in adult rats bilateral nephrectomy (NX) is followed by a significant decrease in its hepatic excretion in dependence on time after kidney removal. In young rats NX is without consequences on hepatic excretion of IGA. It is possible to stimulate renal and/or hepatic excretion of IGA by repeated administration of T3, dexamethasone, or phenobarbital. The effect of stimulation is different in kidney and liver and depends on age, too.

Phenol red mimics biological actions of estradiol: enhancement of osteoblast proliferation in vitro and of type I collagen gene expression in bone and uterus of rats in vivo

Since osteoblasts are direct targets for estradiol in vitro, and Phenol Red has been reported to bear estrogen-like bioactivity, we investigated whether the pH indicator also mimicked the biological effects of estradiol on bone cells in vitro. We then asked whether estrogenic effects of Phenol Red could be observed in vivo, firstly on the uterus, and if so, whether Phenol Red could also effect bone in vivo. The proliferation of calvarial osteoblasts was stimulated by commercially available preparations of Phenol Red in a dose-dependent manner at 1.5-50 microM. This effect was not abolished in the presence of an antibody against insulin-like growth factor I. In addition, Phenol Red increased alpha 1 (I) collagen mRNA levels of osteoblasts in vitro. 17 beta-estradiol (1.5 micrograms) or Phenol Red (10 mg) administration to immature female rats (45-50 g) resulted in a weight gain of the uterus, and alpha 1(I) procollagen transcripts were more abundant in RNA prepared from uterus of drug-treated rats than observed in the control rats. Similarly, higher procollagen mRNA steady-state levels were observed in RNA prepared from parietal bones of Phenol Red or estradiol-treated rats compared to RNA from control rats. The data extend previous findings in vitro by demonstrating that Phenol Red also exerts estrogen-like effects in vivo. Moreover, we show that Phenol Red stimulates bone cells and, therefore, is likely to interfere at least in experiments designed to investigate estrogen effects on osteoblasts.

Sex-related differences in the hepatobiliary transport of phenolsulfonphthalein in the rat

Sex-related differences in the hepatobiliary transport of phenolsulfonphthalein (PSP) were investigated in male and female Wistar rats. Maximal biliary excretion of unconjugated PSP was significantly higher in females while the excretion of the conjugated dye and liver UDP-glucuronosyltransferase activity toward PSP were higher in male animals. Orchidectomy decreased enzyme activity and excretion of the conjugate, whereas ovariectomy produced the opposite effect. Both in gonadectomized males and females maximal biliary excretion of the unconjugated dye was significantly reduced. Testosterone treatment increased the excretion of both conjugated and unconjugated PSP and transferase activity in orchidectomized males. Combined treatment of gonadectomized females with estradiol plus progesterone led to excretions of both conjugated and unconjugated PSP and UDP-glucoronosyltransferase activities similar to those found in control rats. These data indicate the existence of sex-related differences in the conjugation and biliary excretion of PSP in the rat and its modulation by sex hormones.

Relation between renal and hepatic excretion of drugs: XIII. Pharmacokinetics of new antiarrhythmic drug Bonnecor in rats with normal and impaired excretory functions

The clearance of 14C-Bonnecor, a weak organic cation, was measured in anaesthetized rats during 6 h after administration. The drug and its labelled metabolites are excreted both via kidney and liver. The renal excretion dominates especially following high doses. After bile duct ligation the renal excretion of Bonnecor increases significantly whereas in nephrectomized rats the biliary excretion of this substance is distinctly reduced. Plasma protein binding ratios amount to 60-70%. Renal removal of Bonnecor and the formed metabolites is in part a result of glomerular filtration. Increased urinary excretion of 14C-Bonnecor-activity under conditions of forced diuresis indicates the involvement of tubular reabsorption in renal handling of the drug and its metabolites. These in vivo results could be confirmed in experiments on renal cortical slices indicating a distinct tubular transport of the drug and its metabolites. In the kidney the aerobic accumulation of Bonnecor is very effective. Surprisingly, under anaerobic incubation conditions, uptake of Bonnecor into renal tissue remains relatively high indicating a distinct binding of Bonnecor within the tubular cells. In the liver the accumulation of Bonnecor is lower compared to the kidney. Furthermore, enterohepatic circulation of Bonnecor and its metabolites was checked. In animals with intact biliary tract, renal removal of 14C-Bonnecor-activity from the organism is significantly higher than in rats with bile duct cannulation. Reinfusion of bile increased renal excretion of 14C-Bonnecor-activity additionally. Both results indicate an effective intestinal reabsorption and enterohepatic circulation of this drug.

Influence of bile acids on the biliary transport maximum of phenolsulfonphthalein in the rat

1. The effect of changes in bile acid secretion induced by cholestyramine treatment or taurocholate infusion on the biliary transport maximum (Tm) of phenolsulfonphthalein (PSP) was studied in Wistar rats. 2. Five hours after oral administration of cholestyramine (1.5 g/kg bodyweight) the biliary output of bile acids decreased to 51% and bile flow to 76% of control values. The percentage of conjugated and unconjugated PSP excreted into bile and the Tm of the dye were not significantly modified by cholestyramine pretreatment. 3. Administration of sodium taurocholate at increasing rates (60-480 nmol/100 g bodyweight per min) enhanced bile flow and the biliary output of bile acids in a linear dose-related fashion. The Tm of PSP increased progressively until a maximum of 29% above the control values was reached at a taurocholate dose of 240 nmol/100 g bodyweight per min). The enhancement corresponded mainly to the unconjugated dye, the excretion of conjugated PSP not being significantly modified by the infusion of the bile acid. 4. The results indicate that bile acids can influence to some extent biliary excretion of PSP in the rat, although this component is of minor importance at low bile acid secretory rates.

Phenolsulphonphthalein conjugation and biliary excretion in the rat: influence of phenobarbital and 3-methylcholanthrene

The effect of phenobarbital and 3-methylcholanthrene pretreatment on the biliary excretion of phenolsulphonphthalein (PSP) was investigated in male Wistar rats. The dye was injected at a single dose of 200 mumol/kg body wt. About 20% of the compound was excreted as a glucuronide in the controls, the liver UDP-glucuronyltransferase activity toward PSP being 0.064 +/- 0.005 nmol.min-1.mg protein-1. Treatment for two weeks with phenobarbital (354 mumol.kg body wt-1.day-1) caused a transient increase in conjugated and unconjugated PSP excretion, but glucuronyltransferase activity was not modified. 3-Methylcholanthrene pretreatment for 4 days (75 mumol.kg body wt-1.day-1) also enhanced biliary excretion of the dye, but the increase corresponded only to the glucuronide and glucuronyltransferase activity was significantly enhanced by 20%. Our data indicate that not only the rate of biotransformation but also other factors could be responsible for increased PSP biliary excretion following administration of microsomal enzyme inducers.

Relation between renal and hepatic excretion of drugs: X. Excretion of nalorphine in young and adult rats pretreated with hormones or xenobiotics

Different processes are involved in renal and hepatic excretion of organic anions and cations. In contrast to our knowledge of anion excretion, information about cation transport in kidney and liver is relatively scarce. In this study, the elimination of nalorphine was investigated to characterize the relation between renal and hepatic excretion of organic cations. Nalorphine is excreted effectively both via kidney and liver. However, its hepatic excretion dominates in adult rats. In young, 20-day-old animals biliary nalorphine elimination is immature and the excreted amounts are significantly lower. Renal excretion of nalorphine is quite similar in rats of both ages. After bile duct ligation renal excretion of nalorphine increases significantly in adult rats whereas it remains unchanged in young ones. Remarkably, after bilateral nephrectomy hepatic elimination of nalorphine is even diminished in both age groups. In further experiments renal excretion of nalorphine could be stimulated in adult rats after repeated administration of trometamol, triiodothyronine, or dexamethasone; these treatments had no consequences on biliary secretion of nalorphine.

Relation between renal and hepatic excretion in drugs. VIII. Influence of triiodothyronine on maturation of phenol red excretion in rats

Experiments were performed on 10-, 20-, and 55-day-old female rats. Administration of triiodothyronine (T3; 10 or 20 micrograms/100 g b.wt. for 3 days, once daily) was followed by a significant increase in renal phenol red excretion in 20-day-old and older rats. In 10-day-old rats there was no stimulatory effect of T3 on renal excretion of the dye. On the other hand, biliary excretion of phenol red was significantly diminished in all age groups. Surprisingly, in nephrectomized rats there was a significant increase in hepatic dye excretion in 20- and 55-day-old rats after T3. This increase in transport capacity via liver was connected with a distinct rise of bile flow. In experiments on tissue slices phenol red accumulation was investigated at different medium concentrations. In renal cortical slices there was no significant influence of T3 on specific accumulation of phenol red per 1 g organ wet weight, whereas aerobic accumulation of the dye seems to be diminished in liver tissue after T3 treatment. But in all age groups kidney weight increased significantly. Calculation of total accumulation (= specific accumulation x organ wet weight) resulted in a significantly enhanced renal transport capacity for phenol red in all age groups. In contrast, total hepatic accumulation was reduced independently of age.

Relation between renal and hepatic excretion of drugs: VII. Hepatic and renal excretion of phenol red in thioacetamide-induced acute and chronic liver damage

Acute and chronic liver damage was induced in rats by thioacetamide (TAA). Centrilobular liver cell damage associated with an accumulation of lipid droplets was produced by a single high dose (10 mg TAA/100 g b.m.). Liver fibrosis, micronodular and macronodular liver cirrhosis were induced by chronic TAA treatment (300 ml/l drinking water for 1.5, 3 or 6 months). Acute administration of TAA caused a significant decrease of hepatic phenol red excretion but no compensatory increase of its urinary excretion. In contrast, 24 h after bile duct ligation renal excretion of the dye increased by about 50%. After chronic exposure to TAA for three months hepatic phenol red excretion remained reduced and renal excretion raised significantly. This compensatory increase of urinary excreted phenol red amounts did not occur after 6 months of TAA treatment, probably as a result of additional nephrotoxicity of TAA. Two weeks after cessation of TAA exposure for 3 months, hepatic and renal phenol red excretion returned to normal. Bile flow per animal increased significantly after 3 months of TAA exposure. Apparently this is due to a reduced intrahepatic reabsorption of canalicular bile in TAA-damaged liver.

Relation between renal and hepatic excretion of drugs: III. Comparison of various methods reducing the renal or hepatic excretory capacity of rats

In previous investigations bilateral nephrectomy (NX) and bile duct ligation (DL) were used to interrupt the renal or biliary excretion route, respectively. But competent doubt arose concerning the comparability of both interferences. In the case of DL the liver could influence the possible compensatory increase of renal excretion capacity; after removal of both kidneys such feedback on the liver is impossible. Therefore the corresponding operations were tested: bilateral ureter obstruction (UO) and so-called functional hepatectomy (fHX) caused by ligation of the porta hepatis. The time courses of a compensatory intensification of the excretory function of liver or kidney have been demonstrated. The following general conclusions can be drawn: fHX is characterized by some drawbacks because of its severe negative systemic effects. Thus DL should be preferred because the compensatory renal excretion capacity can be investigated without a significant reduction of the animal's vital forces. In contrast, NX seems to be the method of choice interrupting renal excretion. It is possible to remove both kidneys without a disturbance of other organ functions and the unpredictable effects of the hydronephrotic kidneys after UO on the whole organism are excluded. At least it is optimal to perform clearance studies approximately 24 h after both NX/UO or DL, because already at this time the phenomena of compensation have become maximal.

Relation between renal and hepatic excretion of drugs. II. Age-dependence of phenol red excretion in comparison with those of p-aminohippurate and indocyanine green

The excretory functions of kidney and liver do not develop simultaneously during the maturation of an individual. Therefore age related differences in the relation between renal and hepatic drug excretion could be expected. In this study the excretion of p-aminohippurate (PAH) and indocyanine green (ICG) as model substances for nearly exclusive excretion via kidney or liver, respectively, have been compared with that of phenol red eliminated both via kidneys and liver (3:1). Experiments were performed on rats between the 10th and 105th days of life. For PAH and ICG the typical age courses of renal or hepatic excretion have been confirmed. Both urinary and biliary phenol red excretion show an influence of age, however, renal elimination reaches adult values as early as at the 20th day of life. Furthermore the age relation concerning compensation of the loss of kidney or liver excretory functions has been studied. Neither after nephrectomy (NX) nor after bile duct ligation (DL) the PAH or ICG elimination via the alternative pathway, respectively, were quantitatively increased. Thus a compensation of the interruption of the main elimination route does not occur in all ages. In contrast, phenol red excretion into urine and bile increases distinctly after DL or NX. This increase becomes even significant after administration of suitable doses of phenol red saturating transport capacities of liver or kidney. The compensation is first of all caused by passive pharmacokinetic changes. Active compensatory mechanisms have not been proved.