Kinetics of drug action in disease states. XXVI: Effect of fever on the pharmacodynamics of theophylline-induced seizures in rats

This investigation was designed to determine the effect of fever on the neurotoxicity of theophylline as reflected by the concentrations of this drug that cause convulsions in experimental animals. Fever was produced in male, inbred, adult Lewis rats (approximately 180 g) by sc injection of brewer's yeast; an elevation of body temperature of 1.2 +/- 0.4 degrees C (mean +/- SD) was achieved at the time of the pharmacodynamic measurements. Theophylline was infused iv at a rate of 1.03 mg/min until the onset of maximal seizures. Drug concentrations in serum, serum water, brain, and cerebrospinal fluid (CSF) at that time were determined by high-performance liquid chromatography. Compared with the control group, the group of febrile rats had statically significantly lower serum protein concentrations, decreased serum protein binding of theophylline, and slightly increased theophylline concentrations in the CSF at the onset of seizures. Inasmuch as theophylline concentrations in the CSF reflect the concentrations of this drug in the biophase, the results of this study show that fever does not increase the sensitivity of the central nervous system to the neurotoxic effects of theophylline in rats. In fact, a statistically significant positive correlation between theophylline concentrations in the CSF and body temperature was found in this investigation, suggesting a decreased sensitivity of the animals to the neurotoxic effects of theophylline at higher body temperature.

Pharmacodynamics of zoxazolamine and chlorzoxazone in rats

Zoxazolamine is used for the pharmacologic assessment of possible changes in oxidative enzyme activity (paralysis time test) in rodents, whereas one of its metabolites, chlorzoxazone, is used clinically as a skeletal muscle relaxant. In this investigation, the pharmacodynamics of the two compounds were characterized in normal adult rats to determine their suitability for studies of the kinetics of drug action in disease states. Upon i.v. infusion 5 min beyond the onset of loss of the righting reflex (LRR) and concomitant blood sampling, serum concentrations of either drug were higher at the onset than at the offset of LRR, suggestive of a distribution disequilibrium. When zoxazolamine was infused at three different rates to onset of LRR, the pharmacologic end point was reached in 10 to 53 min. Drug concentrations in serum and brain at onset of LRR increased with increasing infusion rate, whereas drug concentrations in cerebrospinal fluid (CSF) were infusion rate independent and essentially identical to CSF concentrations at offset of LRR. Similar experiments (five infusion rates) with chlorzoxazone revealed drug infusion rate dependence even of CSF concentrations at the onset of LRR; only at very slow infusion rates (onset of effect in greater than or equal to 50 min) were onset concentrations in CSF essentially equal to offset concentrations. Neither drug produced measurable metabolite concentrations in the CSF. It is concluded that zoxazolamine but not chlorzoxazone distributes rapidly between CSF and the biophase, metabolites of either drug do not contribute measurably to the pharmacologic effect, and neither drug is subject to development of functional tolerance under the experimental conditions.(ABSTRACT TRUNCATED AT 250 WORDS)

Kinetics of drug action in disease states. XXVII. Effect of experimental renal failure on the pharmacodynamics of zoxazolamine and chlorzoxazone

The purpose of this investigation was to determine whether the pharmacodynamics of the centrally acting skeletal muscle relaxants zoxazolamine (ZOX) and chlorzoxazone (CZX) are altered in renal failure. Male Lewis rats with renal failure due to bilateral ligation of ureters and sham-operated controls (ZOX and CZX), as well as rats with uranyl nitrate-induced renal dysfunction and saline-injected controls (ZOX only), received an infusion of ZOX or CZX until onset of loss of righting reflex. Drug concentrations in serum, brain and cerebrospinal fluid at that time were substantially lower in animals with renal failure or dysfunction than in normal controls. The ZOX concentrations in the cerebrospinal fluid correlated negatively with indices of renal function (serum creatinine and urea concentrations). Administration of a concentrated dialyzate of serum from rats with uranyl nitrate-induced renal dysfunction to normal animals also decreased the concentrations of ZOX at onset of loss of righting reflex. Thus, the sensitivity of the central nervous system of rats to the depressant action of ZOX and CZX is significantly increased by renal failure. This effect appears to be mediated, at least in part, by an endogenous, dialyzable substance that accumulates in the blood of rats with impaired renal function.

Rapid development of functional tolerance to caffeine-induced seizures in rats

The concentration and time dependence of caffeine-induced neurotoxicity was determined by infusing rats intravenously with caffeine at a rate of about 5, 12.5, and 25 mg kg-1 min-1 until the onset of generalized seizures which occurred at about 82, 28, and 11 min, respectively. The concentration of caffeine in the serum, brain, and cerebrospinal fluid at onset of seizures increased with decreasing infusion rate; the concentrations of caffeine metabolites were negligible and serum protein binding was not affected by the infusion rate. In another experiment, one group of rats was infused with caffeine for 60 min at about 2.2 mg kg-1 min-1 whereas another group was infused with solvent only. Both groups were then immediately infused with caffeine at about 22 mg kg-1 min-1 until onset of seizures. Caffeine concentrations at that time in serum, brain, and cerebrospinal fluid were significantly higher in the caffeine-pretreated animals than in the solvent-pretreated controls. The same pretreatment 17 hr before the fast infusion of caffeine had no apparent effect on caffeine concentrations at onset of seizures. These results show that functional tolerance to the seizure-inducing effect of caffeine in rats develops within minutes and that it is reversible within hours or less.

Regional myocardial ajmaline concentration and antiarrhythmic activity for ischaemia- and reperfusion-induced arrhythmias in rats

1. Antiarrhythmic actions of ajmaline against ischaemia (left coronary artery occlusion for 15 min) and subsequent reperfusion-induced arrhythmias were investigated in anaesthetized rats. 2. Ajmaline (2 mg kg-1, i.v.) was effective in suppressing ischaemia-induced arrhythmias whether given pre- or post-occlusion. 3. Ajmaline diminished the reperfusion-induced arrhythmias completely when given pre-occlusion but had little effect when given post-occlusion. 4. Reperfusion-induced increases in plasma enzyme activities of lactate dehydrogenase, glutamate-oxaloacetate transaminase and creatine phosphokinase were prevented more effectively when ajmaline was given pre-occlusion rather than post-occlusion. 5. Fifteen min post-occlusion, the ajmaline concentrations in the ischaemic ventricle were 18.42 +/- 1.66 and 1.18 +/- 0.15 micrograms g-1 for pre- and post-occlusion administration, respectively. However, ajmaline concentrations in whole blood and normal ventricle were not significantly different between pre- and post-occlusion administration. 6. We suggest that the beneficial effect of ajmaline against reperfusion-induced arrhythmias is related to the ischaemic myocardial concentration of ajmaline which is markedly affected by the time of drug administration (i.e. pre- and post-occlusion).

Kinetics of drug action in disease states. XIX. Effect of experimental liver disease on the neurotoxicity of theophylline in rats

There are pronounced interindividual differences in the neurotoxicity of theophylline in humans as reflected by the wide range of plasma theophylline concentrations associated with the occurrence of life-threatening, generalized seizures in patients treated with this widely used bronchodilator. The variability indicates that there may be a number of as yet unrecognized risk factors for theophylline neurotoxicity. After the development of an animal model of theophylline-induced seizures, renal failure was identified as one such risk factor. This investigation was designed to determine if experimental liver disease will alter the neurotoxic effect of theophylline. Studies were performed on rats with extrahepatic cholestasis produced by bile duct ligation and with hepatic necrosis induced by carbon tetrachloride administration and on respective controls. Theophylline was infused i.v. at 1.03 mg/min until the onset of maximal seizures. Theophylline and theophylline metabolite concentrations at that time were determined in serum (unbound and total drug), brain and cerebrospinal fluid. Extrahepatic cholestasis was associated with small increases in unbound theophylline concentration in serum, theophylline concentration in brain and serum free fraction in serum at onset of seizures. The concentrations of theophylline metabolites were negligible. There were no apparent effects of extrahepatic cholestasis or hepatic necrosis on theophylline concentrations at onset of seizures in cerebrospinal fluid, the fluid that was shown in a preceding study to be the best indicator of the theophylline concentration at the site of the neurotoxic effect. It is concluded that experimental liver disease had no apparent effect on the neurotoxicity of theophylline under the conditions of this investigation.

Kinetics of ajmaline disposition and pharmacologic response in beagle dogs

Pharmacokinetics and pharmacodynamics of ajmaline were studied in four healthy dogs after intravenous administration of the drug at the infusion rate of 1.0 mg/min for 45 min. Ajmaline exhibited a saturable binding to plasma protein. One kind of binding site was found in the range of observed drug concentrations and its binding capacity showed nearly threefold interindividual difference. The time course of ajmaline concentration in whole blood Cb could be described by the two-compartment open model and the unbound concentration of ajmaline in plasma Pf was estimated from Cb by using the hematocrit value and the parameters of plasma protein binding and erythrocyte partitioning. The pharmacologic responses to ajmaline were assessed by recording ECG, and the changes in PQ and QRS interval were studied in relation to ajmaline disposition. When ECG changes were related to the ajmaline concentration, a significant degree of hysteresis was observed. The relationship between the unbound drug concentration and the pharmacologic effect was analyzed by a combined pharmacokinetic-pharmacodynamic model, where the hypothetical effect compartment is connected to the Pf in the central compartment by a first-order process. This model allows estimation of the changes in PQ and QRS intervals after intravenous administration of ajmaline. By comparing the drug effect on PQ and QRS intervals, it was suggested that ajmaline distributes to the atrial and the ventricular tissue in a similar degree and causes a reduction in the conduction rate in both sites with similar activity.

Blink reflex elicited by auditory stimulation in the rabbit

The pathway of the blink reflex, elicited by auditory stimulation, was investigated electrophysiologically. The reflex was recorded as microvibrations of the eyelid and was named the auditory-evoked eyelid microvibration (AMV). Pharmacophysiological studies suggest that AMV is closely related to the midbrain reticular formation and studies of electrical lesions in the midbrain reticular formation support this. Lesions in several parts of the central nervous system provide evidence that the inferior colliculus has an important role in AMV, and the cerebral cortex may have an inhibitory influence. Studies of brainstem transections indicate that the reflex pathway of AMV exists between the lower midbrain and the upper medulla. Because of its ease and simplicity, AMV is believed to be a useful test for evaluation of the function of the brainstem.

Degradation of acetaldehyde produced by the nonalcohol dehydrogenase pathway

Acetaldehyde (Ac-CHO) is produced via the oxidation of ethanol by two different pathways; alcohol dehydrogenase (ADH) and non-ADH systems. However, degradation of Ac-CHO in the liver, especially with respect to the relative amounts produced by the two pathways, remains unclear. In order to clarify the metabolic fates of Ac-CHO produced by the two pathways, the ethanol metabolic rate (EMR) and hepatic Ac-CHO levels in the rats fed an alcohol-containing or control diet for 4 weeks were determined after a single administration or constant infusion of ethanol, with or without 4-methylpyrazole pretreatment. The EMR was increased in chronic alcoholic rats and decreased by treatment with 4-methylpyrazole. Consequently, blood and hepatic Ac-CHO levels were low in the pyrazole-treated rats in both the single dose and infusion experiments. Hepatic Ac-CHO levels and EMR were well correlated in both experiments. However, the correlations were curve linear and the slopes of the regression lines in the pyrazole-treated rats were steeper than those in the nontreated rats. When the ratios of hepatic Ac-CHO (subtracted by a constant which was obtained from the correlation equations for the curvilinear fit of hepatic Ac-CHO levels and EMR) to EMR were calculated, they were significantly higher in the pyrazole-treated rats than in the nontreated rats of the perfusion experiment, without relation to chronic alcohol ingestion. These results suggest that Ac-CHO produced by the non-ADH pathway degrades more slowly than that produced by the ADH pathway in the liver.

Pharmacokinetics and antiarrhythmic activity of ajmaline in rats subjected to coronary artery occlusion

The pharmacokinetics and the antiarrhythmic action of intravenous ajmaline were investigated in anaesthetized rats subjected to coronary artery occlusion. Ajmaline (0.125-2 mg kg-1, i.v. given just after occlusion) suppressed arrhythmias in a dose-dependent manner, judged by the reduction of premature ventricular complexes. The incidence of malignant arrhythmias (ventricular tachycardia and fibrillation) was preferentially suppressed at the higher doses of ajmaline (1 and 2 mg kg-1). Coronary occlusion induced a change in pharmacokinetics of ajmaline (2 mg kg-1) and its total body blood clearance was significantly decreased from 56.6 ml min-1 kg-1 in sham-operated rats to 43.1 ml min-1 kg-1 in rats after coronary occlusion. Ajmaline exhibited a significantly increased negative dromotropic action (increased PQ interval) in rats after coronary occlusion compared with that in sham-operated rats. The difference seems to be due to the pharmacokinetic change since the concentration-effect relationship was similar in the two groups of rats. We suggest that the measurement of drug levels is important in the assessment of antiarrhythmic agents.

Mechanisms of pharmacokinetic interaction between ajmaline and quinidine in rats

In order to elucidate the mechanism of ajmaline-quinidine interaction previously observed in humans, the effects of quinidine on pharmacokinetics of ajmaline were investigated in rats. Concurrent oral administration of 10 mg/kg of quinidine markedly increased the plasma concentration of ajmaline at a dose of 2 mg/kg. On the other hand, it did not affect the pharmacokinetics of ajmaline after intravenous dose. The availability of ajmaline after oral dose showed an increase from 13% to nearly 100% by the presence of quinidine, which suggests a change in the presystemic clearance of ajmaline. In fact, when ajmaline was administered into the intestinal loop, its concentration in mesenteric venous plasma increased approximately 5-fold by the combination with quinidine. Furthermore, quinidine delayed the elimination rate of ajmaline from the perfused rat liver. These results indicate that quinidine prevents presystemic elimination of ajmaline in the intestine and liver, and increases the systemic availability of ajmaline.

An analysis program MULTI(ELS) based on extended nonlinear least squares method for microcomputers

An analysis program MULTI(ELS) was developed for population pharmacokinetics on a microcomputer. The program based on the extended least squares (ELS) is written in the Microsoft minimum BASIC command alone. ELS simultaneously estimates not only the population pharmacokinetic parameters but also the variances of inter-individual variabilities around the population parameters and of intra-individual variabilities for the plural time courses, whereas the ordinary least squares estimates the pharmacokinetic parameters of each time course. Two least squares algorithms (i.e. quasi-Newton and simplex methods) are provided in MULTI(ELS). MULTI(ELS) was compared with NONMEM (Version I, Level 3) developed by Sheiner and Beal for several time course data. It was shown that MULTI(ELS) gave the same results as NONMEM. MULTI(ELS) calculates the Akaike's information criterion (AIC) for the extended least squares. It was also shown that the AIC is effective in comparing the population characteristics of time courses in a group with those in another group and in verifying the model structures of population means, inter-individual variations and intra-individual variations.

Effect of altered plasma protein binding on pharmacokinetics and pharmacodynamics of propranolol in rats after surgery: role of alpha-1-acid glycoprotein

The pharmacokinetics and pharmacodynamics of propranolol in rats 2 days after laparotomy were compared to control animals. The apparent volumes of distribution and the systemic clearance of propranolol were decreased to about 20 to 40 and 70% of control values, respectively. The area under the blood concentration-time curve (AUC) of propranolol after p.o. administration showed a marked elevation after surgery and its availability increased about 2-fold at doses of 5.0 and 12.5 mg/kg. These changes were associated with a decreased plasma unbound fraction of propranolol after surgery. Immunological determination of alpha-1-acid glycoprotein (AGP) revealed a marked increase after laparotomy and a linear relationship was found between the plasma AGP concentration and the binding capacity of high-affinity binding site for propranolol in plasma (r = 0.961, P less than .001). AUC of p.o. administered propranolol was also correlated with plasma AGP concentration. The beta-blocking activity of propranolol assessed by the reduction in the isoproterenol-induced tachycardia was decreased in rats after laparotomy when it was evaluated in terms of the total plasma concentration of propranolol. In contrast, its activity evaluated by the unbound plasma concentration showed no difference between control and laparotomized rats, suggesting the dependence of the pharmacological activity of propranolol on its unbound level in plasma. Thus, laparotomy-induced changes in both pharmacokinetics and pharmacodynamics could be considered largely due to an increase in its binding to the increased plasma level of AGP.

Identification of the major binding protein of salmon calcitonin in the rat

The major serum binding protein of salmon calcitonin (sCT) in the rat was identified. High-molecular-weight (HMW) forms of sCT, produced by the incubation of radioactive sCT in rat serum, were isolated by gel filtration and analysed by chromatofocusing. The major radioactive peak was eluted at the region of albumin in gel filtration, and this peak had a slightly higher pI than albumin on chromatofocusing. Immunoreactivity of the radioactive peak fraction in chromatofocusing, examined by immunodiffusion, showed that the major protein in the fraction was albumin. Immunoreactivity of the radioactive HMW fraction isolated by gel filtration was studied by immunoprecipitation, indicating that a large portion of the fraction reacted with anti-rat albumin antiserum. These results suggested that the radioactive peak in chromatofocusing represents the complex of sCT and rat albumin. Further, HMW forms of sCT were analysed by immunoelectrophoresis and autoradiography, and most of the radioactivity was found on the precipitation line of albumin. These results demonstrate that the major binding protein of sCT in rat serum is albumin.

Reduced hepatic uptake of propranolol in rats with acute renal failure

The effect of acute renal failure (ARF) on the hepatic uptake and metabolism of propranolol was investigated in relation to the hepatic clearance of the drug. ARF was induced by the subcutaneous injection of uranyl nitrate to rats. The uptake rate of propranolol in the isolated perfused liver was determined by the multiple-indicator dilution method and was found to decrease from 43.6 +/- 2.0 min-1 (mean +/- S.E.) in control to 29.4 +/- 1.7 min-1 in ARF (P less than 0.001). The recovery fraction of propranolol in effluent venous blood increased about twofold in ARF compared to control (P less than 0.05). The metabolic activity for propranolol was examined using the hepatic microsomal fraction prepared from control and ARF rats. There was no significant difference in the kinetics of oxidative metabolism of propranolol between two groups. These results suggest that the previously reported decrease in the hepatic clearance of propranolol in ARF is due to decreased hepatic uptake of the drug from the blood into the liver cells.

Comparison between ballooned hepatocytes occurring in human alcoholic and nonalcoholic liver diseases

To establish clearly what the pathogenetic differences are in the hepatocytic ballooning between human alcoholic and nonalcoholic liver diseases, hepatic microtubules were examined by morphometric and biochemical methods, and staining of transferrin was carried out on liver sections immunohistochemically. Microheterogeneity of serum transferrin was also detected by immunofixation after isoelectric focusing. Hepatic microtubules were significantly decreased in alcoholic liver disease, and transferrin was clearly stained in the ballooned hepatocytes of alcoholic liver disease but not in nonalcoholic liver disease. The degree to which transferrin was stained was related to hepatic microtubular contents and also related to the appearance of the microheterogeneity of serum transferrin in alcoholic liver disease. These findings indicate that ballooning of hepatocytes in alcoholic liver disease, but not in nonalcoholic liver disease, is caused by the accumulation of exportable proteins due to impairment of microtubular polymerization. This accumulation might be related to the inhibition of glycosylation and secretion of glycoproteins by the impairment of microtubular functions. From these results, it was determined that staining of transferrin in the liver may be useful for differentiation of the etiology of liver diseases.

Influence of acute renal failure on pharmacokinetics of phenolsulfonphthalein in rats: a comparative study in vivo and in the simultaneous perfusion system of liver and kidney

The effect of acute renal failure (ARF) on the disposition of phenolsulfonphthalein (PSP) after intravenous administration was investigated in rats. ARF was induced by the subcutaneous injection of uranyl nitrate to rats. Renal excretion of PSP decreased significantly in ARF compared to that in normal controls. On the other hand, rats with ARF showed an increased biliary excretion of PSP to compensate for reduced renal excretion of the drug. Consequently no significant change was found in total body clearance of PSP between control and ARF. The in vitro binding experiment showed that the binding fraction of PSP to ARF plasma was significantly lower than that to control plasma. In order to clarify the regulatory mechanisms of PSP excretion between liver and kidney in ARF, we developed a simultaneous perfusion system of rat liver and kidney, which could control the flow rate and the constituent of the perfusate. In this perfusion system, neither biliary excretion nor the protein binding of PSP differed significantly between control and ARF, though its renal excretion decreased in ARF in a similar manner as in vivo. These results suggest that alterations in plasma protein binding as well as renal excretory function are determinants of PSP disposition in ARF.

[So-called "carcinoid tumor of the breast"--a case report]

A 70-year-old woman underwent modified radical mastectomy following excisional biopsy of a right breast mass. The excised tumor was 1.4 cm in diameter. The mastectomy specimen and lymph nodes were negative for malignancy. Histologically, the tumor cells were mainly oval and had formed solid nests in the thick fibrous stroma. The cytoplasm was fine granular and contained many argyrophilic granules. The argentaffin reaction was negative. Electron microscopy revealed oval-shaped light cells and stellate-shaped dark cells. Both types of tumor cells contained abundant filaments, well-developed rough surfaced endoplasmic reticulum and many neurosecretory-type granules measuring 190 approximately 360 nm in diameter. Intracytoplasmic lumina were not discerned. The relationship between carcinoid and conventional breast carcinoma was discussed.

A nonlinear multiple regression program, MULTI2 (BAYES), based on Bayesian algorithm for microcomputers

A nonlinear multiple regression analysis program MULTI2(BAYES) was developed for microcomputers. The Bayesian algorithm which is incorporated in MULTI2 (BAYES) combines the insufficient individual patient data (individual data) with the pharmacokinetic parameters published in literatures (population parameters) to predict the plasma time course of the patient. The program is written in the minimum Microsoft BASIC commands alone to be executable on many personal computers without any modification. The numbers of parameters to estimate, independent variables and dependent variables are not restricted in use of MULTI2(BAYES). The pharmacokinetic models are defined as one pleases by the user. The four nonlinear least squares algorithms, i.e. Gauss-Newton method, damping Gauss-Newton method, modified Marquardt method by Fletcher and simplex method can be selected at user's option. MULTI2(BAYES) calculates the confidence limits of time courses at 95% significant level.

Comparison of ballooned hepatocytes in alcoholic and non-alcoholic liver injury in rats

Ballooned hepatocytes are commonly observed in alcoholic and sometimes in non-alcoholic liver diseases. To clarify whether pathogenesis of this change is different in alcoholic and non-alcoholic liver diseases, changes of the livers in rats fed alcohol with pyrazole for 12 weeks were compared with those of CCl4 treated rats. Both groups of rats showed marked ballooning of the hepatocytes in the centrolobular area. Immunohistochemically, the ballooned hepatocytes in alcohol-pyrazole treated rats reacted strongly with transferrin and albumin staining. However, staining reaction of the ballooned hepatocytes in the CCl4 treated rats was slight. In alcohol-pyrazole treated rats, hepatic microtubules were significantly decreased. Retention of transferrin and albumin were found only in the ballooned hepatocytes of alcohol-pyrazole treated rats. However, in the CCl4 treated rats, neither microtubular alteration nor retention of the exportable proteins was observed. These findings indicate that the pathogenesis of ballooning of hepatocytes is different in alcoholic and non-alcoholic liver injuries. In alcoholic liver injury, microtubular alteration may lead to retention of protein and ballooning of hepatocytes by interfering with the hepatic secretion of proteins.

High molecular weight derivative of salmon calcitonin with prolonged hypocalcemic activity

A new method preparing a long-acting formula of salmon calcitonin, which possesses high specific activity, has been developed. This method consists of two processes: (a) preparation of a high molecular weight derivative of salmon calcitonin and (b) preparation of a zinc suspension of the derivative. The derivative was prepared by the incubation of reduced salmon calcitonin with bovine serum albumin. Although it retained almost the same biological activity as the original calcitonin, it was not longer acting. Addition of zinc to the solution of the derivative resulted in a suspension with biological activity significantly longer than the original calcitonin. This procedure is described for obtaining a sustained-release preparation of salmon calcitonin, which might be useful for other peptide drugs.

Distribution of patients' test values and applicability of "average of normals" method to quality-control of radioimmunoassays

Applicability of the Hoffmann's average of normals (Mn) method was evaluated in quality control (QC) of radioimmunoassays (RIA) for thyroxine, 3,5,3'-tri-iodothyronine, thyrotropin, and insulin--assays that are performed routinely in the authors' laboratory. In the first three RIAs, the patterns of the distributions were almost constant and Mn showed significant correlations with values of QC sera and intercepts of the dose-response curve. In insulin RIA, the patterns varied appreciably and Mn showed correlations with parameters that reflect a disturbance in the distribution. Exclusion of assays with abnormal distributions, however, resulted in better correlations of Mn with other QC parameters. These results suggest that average of normals method can be a very useful adjunct to conventional QC methods for RIA. The possibility that the method may be affected by a disturbance in the distribution can be monitored by computation of parameters reflecting such disturbance.

In vivo conversion of peptide drugs into high molecular weight forms

Following injection of 125I-porcine insulin, 125I-aprotinin, 125I-salmon calcitonin, or 125I-(Asu1,7)-eel calcitonin into rats, high molecular weight (HMW) forms of these peptides were detected in serum or plasma when analyzed by gel chromatography. The conversion into HMW forms occurred after 1) intravenous bolus injection of insulin, aprotinin, or calcitonins, 2) intravenous infusion of insulin or aprotinin, and 3) subcutaneous injection of insulin, indicating that HMW forms were produced in the general circulation not in the subcutaneous tissue. Rechromatography of HMW forms produced in vivo from insulin or aprotinin showed the release of lower molecular weight component which was eluted at the same position of parent peptide, the immunoreactivity of the released component derived from insulin was almost the same as for insulin. These results suggest that the conversion of peptide drugs into HMW forms is generally occurred in vivo and they play a role as a depot in circulation.

Characterization of high molecular weight forms of peptide drugs in vivo

Studies were undertaken to investigate the site and conversion mechanism of exogenous peptides into high molecular weight (HMW) forms when administered in vivo. Functional nephrectomy reduced the conversion of aprotinin into HMW form in circulation whereas incubation of aprotinin in kidney homogenate in vitro resulted in an increase in HMW component, indicating that the kidney participates in conversion of aprotinin into HMW form. Incubation of aprotinin in rat serum showed that HMW forms can be produced in blood. Analysis of molecular weight of the components produced in vivo and in serum in vitro demonstrated that they consist of heterogeneous mixture and that the components produced in vitro resemble those produced in vivo. Incubation of (Asu1,7)-eel calcitonin, which lacks intramolecular disulfide bonds, in serum did not result in the production of HMW form, whereas incubation of three other peptides having intramolecular disulfide bonds did, suggesting that conversion mechanism of peptide drugs into HMW forms in blood is mainly by thiol-disulfide interchange reaction between peptides and serum protein.

Drug elimination function of rat small intestine: metabolism and intraluminal excretion

The metabolic and excretory function of the small intestine was investigated after oral and intravenous administration of drugs having an aromatic amino group to rats. After administration of drugs into the intestinal loop at the initial concentration of 0.1 mM, significant excretion of their N-acetylated forms into the lumen was observed. The amount of N-acetyl forms excreted in the lumen were 39.3 +/- 3.5, 63.5 +/- 20.9 and 18.0 +/- 13.8% of disappeared drugs from the lumen for p-aminobenzoic acid (PABA), p-aminosalicylic acid and sulfanilic acid, respectively. The excretion of p-acetamidobenzoic acid (Ac-PABA) after the absorption of PABA was reduced by the coadministration with salicylic acid, benzoic acid and 2,4-dinitrophenol. Salicylic acid noncompetitively inhibited the acetylation of PABA by the intestinal N-acetyltransferase. A good correlation was found between the intestinal N-acetyltransferase activities for drugs and the intraluminal excretion of N-acetyl derivatives after intestinal absorption of drugs. These results indicate that a drug having a higher susceptibility to intestinal N-acetyltransferase would undergo a greater excretion into the lumen in its N-acetyl form after intestinal absorption. After intravenous administration of PABA at a dose of 100 mumole/kg, 4.02 +/- 0.51% of dose was excreted in the lumen as Ac-PABA in 30 min. On the other hand, a significantly smaller fraction (2.72 +/- 0.68% of dose) was excreted in the lumen after intravenous injection of 100 mumole/kg of Ac-PABA. The larger excretion of Ac-PABA after administration of PABA indicates the contribution of intestinal metabolism on the transfer of PABA not only after oral, but also after intravenous administration.

Increased availability of propranolol in rats with uranyl nitrate-induced acute renal failure

The effect of acute renal failure (ARF) on the pharmacokinetics of propranolol was investigated. The model of ARF was produced by the subcutaneous injection of uranyl nitrate to rats (10 mg/kg) and was used 3 d after treatment. Uranyl nitrate-treated rats showed significantly higher plasma concentrations of propranolol after oral administration and the area under the plasma concentration-time curve increased about 3-fold compared to control rats. The plasma disappearance of propranolol after intravenous administration did not differ significantly between control and ARF. The mean availability of propranolol after oral administration increased from 0.120 in control to 0.215 in ARF (p less than 0.005). Absorption of propranolol was almost complete and no significant difference was found between two groups. No changes in plasma protein binding of propranolol and hepatic blood flow were observed in ARF. On the other hand, hepatic clearance of propranolol determined by liver perfusion studies showed a significant reduction in ARF and the calculated intrinsic clearance of unbound propranolol at a dose of 6.25 mg was 26.8 +/- 2.3 ml/min in control and 16.0 +/- 2.3 ml/min in ARF (p less than 0.01). These results demonstrate that the oral availability of propranolol increased in ARF due to a reduction in the hepatic presystemic elimination as compared to healthy control rats.

Quinidine-induced rise in ajmaline plasma concentration

A high-performance liquid chromatographic method is described for the simultaneous determination of ajmaline and quinidine in human plasma. With 0.5 ml plasma sample of a ajmaline and quinidine, concentrations as low as 0.001 and 0.01 micrograms ml-1, respectively, could be detected and the technique could be used to investigate the effect of quinidine on the pharmacokinetics of ajmaline. Four healthy subjects were given oral ajmaline (50 mg) alone or in combination with quinidine sulphate (200 mg) on separate occasions. When ajmaline was administered alone, its plasma concentrations were less than 0.03 micrograms ml-1. Quinidine induced a marked increase to give a mean peak concentration of ajmaline which increased from 0.018 micrograms ml-1 after a single administration to 0.141 micrograms ml-1 in combination with quinidine. the area under the ajmaline concentration-time curves was increased 10 to 30-fold by the concurrent administration of quinidine. According to the one compartment open model, the absorption rate constant of ajmaline did not change appreciably, but the elimination rate constant was reduced to approximately 50% of the value in the absence of quinidine. The results indicate the existence of a significant interaction between oral ajmaline and quinidine.

Automated enzymatic determination of serum and urine creatine using the Abbott ABA-200

A new enzymatic method is described for the determination of creatine in serum and urine with Abbott ABA-200. The measurement is accomplished by transforming creatine to formic acid in a reaction catalyzed by creatinase (creatine amidinohydrolase), sarcosine oxidase and formaldehyde dehydrogenase (see Figure 1). The assay takes less than 20 minutes. The standard response is linear for creatine concentrations up to 10 mg/dL (serum) and 80 mg/dL (urine). The coefficients of variation at 0.69 mg/dL (serum) and 4.93 mg/dL (urine) for within-day determination were less than 4% and, for between-day determination, were less than 5%. Results obtained by this procedure on one hundred serum and urine samples conformed well with a manual enzymatic method and the Folin method. The method is useful for the automated measurement of creatine in serum and urine.

Effects of TRH-T and DN-1417 on the central nervous system: an electrophysiological study of arousal reaction and evoked muscular discharges

For the purpose of elucidating the effects of TRH and DN-1417 on the CNS, electrophysiological experiments were performed and the following observed. 1. TRH and DN-1417 exerted threshold-decreasing action not only on the threshold for arousal reaction but also on the threshold for evoked muscular discharges, which occur on stimulation of the brainstem reticular formation. 2. The threshold decreasing effect of DN-1417 was stronger than that of TRH, not only for the arousal reaction but also for the evoked muscular discharges. 3. Both TRH and DN-1417, with facilitating effects on the brainstem reticular formation, increased the number of spontaneous unit discharges. DN-1417 increased the number of reticular units, to the same degree as TRH with a smaller dose. These results indicate that both TRH and DN-1417 act on the nerve cells in the brainstem reticular formation, awaken consciousness and facilitate the function of the motor system.

Transport characteristics of p-acetamidobenzoic acid in brush border membrane of rat small intestine

Brush border membrane vesicles of rat small intestinal mucosa were prepared by the modified calcium precipitation method in order to investigate the intestinal secretion mechanism of p-acetamidobenzoic acid (Ac-PABA). The release rate of [14C]-Ac-PABA from preloaded vesicles was much faster than that of p-aminobenzoic acid (PABA) and was enhanced by the addition of unlabelled Ac-PABA in the outer medium. In contrast, the membrane transfer rate of Ac-PABA across the egg lecithin liposomes was slower than that of PABA. The contribution of a carrier-mediated transport mechanism in the brush border membrane to the intestinal secretion of Ac-PABA was suggested.

Potential changes and eyelid microvibration elicited by flash stimulation

The photopalpebral reflex evoked in the upper eyelid of the rabbit by flash stimulation was studied in terms of potential change (PPR) and microvibration (MV) and the following conclusions drawn. (1) Of the PPR components, the early components from PPR1 to PPR4 are mainly ERG components, while PPR5 to PPR9 and MV are components appearing via the central nervous system. (2) Excitation of the brainstem reticular formation is involved in the appearance of the central PPR components and MV. Components PPR6 to PPR8 and MV originate in excitation of the same nervous tissue, but PPR9 occurs by excitation of different nervous tissue. (3) Contraction of the extraocular muscles, as well as the orbicularis oculi muscles, is involved in the appearance of MV. (4) Unit discharge takes place in the brainstem reticular formation coinciding with the occurrence of MV and an increase in discharge takes place later. The relation of the increase in this late discharge to PPR9 must be further investigated.

A new enzymatic method to determine creatine

A new enzymatic method is described for the determination of creatine in serum and urine using creatine amidinohydrolase (EC 3.5.3.3), sarcosine oxidase (EC 1.5.99.1) and formaldehyde dehydrogenase (EC 1.2.1.1). The principle of the method is as follows. Creatine is degraded to sarcosine and urea, and the sarcosine formed is measured with sarcosine oxidase in the presence of formaldehyde dehydrogenase and NAD+. The NADH + H+ produced is measured at 340 nm. Creatine concentration can be calculated directly from the absorptivity of NADH + H+ generated in the reaction or from creatine standard solutions. The assay takes less than 20 min. The standard curve is linear up to 50 mg creatine/1 (serum) and 800 mg creatine/1 (urine). Fifty random samples were assayed by this method (y) and simultaneously by the Folin method (x). The correlation coefficients were 0.995 for serum samples, 0.994 for urine samples, and the regression equations were y = 0.979x - 0.01 (serum) and y = 0.978x - 0.01 (urine).

Effects of hyperosmolality on the central nervous system and intracranial hemorrhage

The relationship between hyperosmolality and intracranial hemorrhage as well as brain dysfunction was studied. Hyperosmolality was induced by continuous infusion of hyperosmotic solutions, such as 7% sodium bicarbonate (1,666 mOsm/1), 4.64% sodium chloride (1,666 mOsm/1), 20% glucose (about 1,200 mOsm/1), 20% mannitol (about 1,200 mOsm/1), and 10% glycerol with 0.9% sodium chloride and 5% fructose (about 2,000 mOsm/1). 1) Intracranial hemorrhage was observed without exception after the rabbits had died of hyperosmolality due to the infusion of these agents. The intracranial hemorrhage was mostly subdural hemorrhage in the subtentorial region. 2) The plasma osmolality just before death varied according to the agents administered and was lowest in the case of 7% sodium bicarbonate with a level of 441 mOsm/1. 3) The plasma osmolality in the case of 10% glycerol was higher than the case of 20% mannitol at the death. 4) The arousal reaction was suppressed by hyperosmotic solutions which contain sodium ions, and when the plasma osmolality surpassed 320 mOsm/1, dysfunction of the CNS began to appear. 5) The evoked muscular discharges caused by stimulation of the midbrain reticular formation were suppressed only by the administration of 7% sodium bicarbonate, so this result is related to alkalosis.

Continuous-flow enzymic determination of creatine in urine

A new enzymic method is described for the determination of creatine in urine by continuous-flow analysis. The measurement is accomplished by transforming creatine to formaldehyde in reactions catalyzed by creatinase (creatine amidinohydrolase) and sarcosine dehydrogenase. The formaldehyde is reacted with 4-amino-3-hydrazino-5-mercapto-1,2,4-triazole to form a purple product, which is measured colorimetrically. The method gives a linear standard curve for creatine concentrations up to 100 mg/L. Precision and analytical recovery are excellent, and results correlate well with those by the more-difficult Folin method, which currently is most often used for this analysis.

Continuous-flow enzymic determination of creatine in urine

A new enzymic method is described for the determination of creatine in urine by continuous-flow analysis. The measurement is accomplished by transforming creatine to formaldehyde in reactions catalyzed by creatinase (creatine amidinohydrolase) and sarcosine dehydrogenase. The formaldehyde is reacted with 4-amino-3-hydrazino-5-mercapto-1,2,4-triazole to form a purple product, which is measured colorimetrically. The method gives a linear standard curve for creatine concentrations up to 100 mg/L. Precision and analytical recovery are excellent, and results correlate well with those by the more-difficult Folin method, which currently is most often used for this analysis.

Occurrence of bile alcohol glucuronides in bile of patients with cerebrotendinous xanthomatosis

Using thin-layer chromatography, bile alcohol glucuronides were found with taurine- and glycine-conjugated bile acids in the bile of four patients with cerebrotendinous xanthomatosis. The concentration of the bile alcohol glucuronides was 1.7-5.2 times higher than that of the conjugated bile acids. Detectable amounts of unconjugated bile alcohols were not found in the bile of these patients. The bile alcohol glucuronides were isolated from the bile of one of the patients by means of preparative thin-layer chromatography. Treatment with beta-glucuronidase of the bile alcohol glucuronides liberated glucuronic acid and a mixture of bile alcohols. More than 90% of the liberated bile alcohols was 5 beta-cholestane-3 alpha, 7 alpha, 25-tetrol, and lesser amounts of 5 beta-cholestane-3 alpha, 7 alpha, 12 alpha, 23-tetrol, 5 beta-cholestane-3 alpha, 7 alpha, 12 alpha, 24-tetrol, 5 beta-cholestane-3 alpha, 7 alpha, 12 alpha, 23, 25-pentol, and 5 beta-cholestane-3 alpha,-7 alpha, 12 alpha, 24 alpha, 25-pentol were also obtained. The bile alcohol glucuronides were not oxidized by the treatment with 3 alpha-hydroxysteroid dehydrogenase, indicating that the glucuronide moiety was at 3 alpha-hydroxyl position of the bile alcohols. Comparison of the mass spectra of the acetylated and methylated derivatives of the natural glucuronides and the synthetic 7 alpha, 12 alpha, 25-triacetoxy-5 beta-cholestan-3 alpha-O-(methyl 2,3,4-tri-O-acetyl-beta-D-glucopyranosyluronate) also indicated that the bile alcohol glucuronides consisted of mainly 5 beta - cholestane - 3 alpha, 7 alpha, 12 alpha, 25 - tetrol - glucuronide.

The use of liposomes as a model for drug absorption: beta-lactam antibiotics

Liposomes were prepared from egg phosphatidylcholine-cholesterol-diacetylphosphate (80:20:5) and total lipid extracts of rat intestinal mucosa, and the permeabilty of the liposomal membrane to eight beta-lactam antibiotics was studied by using a dynamic dialysis method. Although all the antibiotics used here are ionized and poorly lipid-soluble at pH 6.5, some of them are orally active and efficiently absorbed from the small intestine. The release rate constants from the aqueous dispersion of drug-entrapped liposomes were approximately in the order of their absorbability. Intestinal lipid liposomes were more permeable to the antibiotics than egg lecithin liposomes and the release rate constants for the drugs from intestinal lipid liposomes were strongly correlative with their absorption rate constants, except for cephalothin and ampicilin, the deviations of which could be explained by their surface activity. It is suggested that lipid components of the intestinal mucosa and the bilayer structure may play an important role in the absorption process of the antibiotics. The validity of liposomes as a model for the intestinal absorption of drugs is also discussed.

Bile salts of frogs: a new higher bile acid, 3 alpha, 7 alpha, 12 alpha, 26-tetrahydroxy-5 beta-cholestanoic acid from the bile Rana plancyi

Bile salts of ten species of frogs of the family Ranidae were examined by means of thin-layer chromatography, gas-liquid chromatography, and gas-liquid chromatography-mass spectrometry. Their major bile alcohols were ranol, cyprinol, or bufol. Four species of frogs contained lesser amounts of higher bile acids, and in two species C24 bile acids were present. A higher bile acid that has not been previously described was detected in Rana plancyi. On the basis of the spectral data and the direct comparison with a synthetic sample, the chemical structure of the new bile acid was established to be 3 alpha, 7 alpha, 12 alpha, 26-tetrahydroxy-5 beta-cholestanoic acid.

The effects of metabolism improving agents: an electrophysiological study

The effects of ATP, cytochrome C, meclofenoxate and CDP-choline on the central nervous system were studied electrophysiologically in rabbits. The threshold of arousal reaction and evoked muscular discharges following stimulation of the brainstem reticular formation, evoked muscular discharges in the fore- and hindlimbs on stimulation of the cerebral cortex and the hippocampus, afferent average evoked potential due to stimulation of the sciatic nerve and unit discharges of nerve cells in the brainstem reticular formation were examined. The results indicate that ATP facilitated the sensory system, cytochrome C facilitated the motor system and meclofenoxate and CDP-choline acted on both systems, but meclofenoxate had activity more like ATP, and CDP-choline had activity more closely allied to that of cytochrome C.

Identifications of 5 beta-cholestane-3 alpha, 7 alpha, 12 alpha, 23 beta-tetrol, 5 beta-cholestane-3 alpha, 7 alpha, 12 alpha, 24 alpha-tetrol, and 5 beta-cholestane-3 alpha, 7 alpha, 12 alpha, 24 beta-tetrol in cerebrotendinous xanthomatosis

The bile alcohols present in the feces of a patient with cerebrotendinous xanthomatosis were studied. Three bile alcohols which are different from any known natural bile alcohol were isolated as minor components of the fecal bile alcohol fraction. The structures of these compounds were established as 5 beta-cholestane-3 alpha, 7 alpha, 12 alpha, 23 beta-tetrol, 5 beta-cholestane-3 alpha, 7 alpha, 12 alpha, 24 alpha-tetrol, and 5 beta-cholestane-3 alpha, 7 alpha, 12 alpha, 24 beta-tetrol by comparison with synthetic samples.