Effect of Beta-Adrenergic Stimulation on the Circulatory Lymphocyte Count: Studies in Normals and in Patients with Chronic Airflow Obstruction

In eight non-allergic patients with chronic airflow obstruction (CAO) and eight age and sex matched, healthy control subjects the circadian variation in circulatory lymphocyte count was studied in relation to serum Cortisol and urinary epinephrine levels. In addition, we investigated the effect of the beta-adrenergic agent terbutaline on the lymphocyte count in two ways: as a long-term effect after 8 days of oral slow-release terbutaline with constant diurnal and nocturnal serum levels in patients, and as a short-term effect by a constant rate infusion of 0.2μg/min over 4hr in normals. Both patients and controls showed similar circadian patterns of urinary epinephrine excretion and lymphocyte counts. Patients with CAO, however, had significantly lower epinephrine levels and significantly higher lymphocyte counts at all hours of observation (every 4 hr from 0800 to 0800 hr the next day), as compared with normal controls. After 8 days of slow-release terbutaline the lymphocyte count in the patient group decreased to levels not significantly different from that of normals. The circadian rhythm of the lymphocytes, however, persisted under terbutaline therapy. No correlation existed between the lymphocyte count modulating factor, serum Cortisol and the lymphocyte count over 24 hr. On placebo infusion in the control persons an increase of lymphocytes over 4hr occurred, as a consequence of circadian rhythmicity. On terbutaline infusion a significant increase of lymphocytes after 1hr was follwed by a decrease to levels significantly below those on the placebo day. The same pattern was found in the leucocyte count. From this study it is concluded that beta-adrenergic stimulation corrects the relative lymphocytosis to counts comparable with normals. Other coinciding factors must regulate, however, the circadian rhythmicity.     

Effect of Beta-Adrenergic Stimulation on the Circulatory Lymphocyte Count: Studies in Normals and in Patients with Chronic Airflow Obstruction

In eight non-allergic patients with chronic airflow obstruction (CAO) and eight age and sex matched, healthy control subjects the circadian variation in circulatory lymphocyte count was studied in relation to serum Cortisol and urinary epinephrine levels. In addition, we investigated the effect of the beta-adrenergic agent terbutaline on the lymphocyte count in two ways: as a long-term effect after 8 days of oral slow-release terbutaline with constant diurnal and nocturnal serum levels in patients, and as a short-term effect by a constant rate infusion of 0.2μg/min over 4hr in normals. Both patients and controls showed similar circadian patterns of urinary epinephrine excretion and lymphocyte counts. Patients with CAO, however, had significantly lower epinephrine levels and significantly higher lymphocyte counts at all hours of observation (every 4 hr from 0800 to 0800 hr the next day), as compared with normal controls. After 8 days of slow-release terbutaline the lymphocyte count in the patient group decreased to levels not significantly different from that of normals. The circadian rhythm of the lymphocytes, however, persisted under terbutaline therapy. No correlation existed between the lymphocyte count modulating factor, serum Cortisol and the lymphocyte count over 24 hr. On placebo infusion in the control persons an increase of lymphocytes over 4hr occurred, as a consequence of circadian rhythmicity. On terbutaline infusion a significant increase of lymphocytes after 1hr was follwed by a decrease to levels significantly below those on the placebo day. The same pattern was found in the leucocyte count. From this study it is concluded that beta-adrenergic stimulation corrects the relative lymphocytosis to counts comparable with normals. Other coinciding factors must regulate, however, the circadian rhythmicity.     

Circadian Rhythm in Gamma Glutamyltranspeptidase and Leucine Aminopeptidase Urinary Activity in Rats

Urinary gamma glutamyltranspeptidase (GGT) and leucine aminopeptidase (LAP), renal tubular brush border enzymes, have been shown to be sensitive indicators of renal tubular functions. This study documents circadian rhythms in the urinary activity of GGT and LAP, statistically validated and quantified by the cosinor method, in 15 male Wistar rats standardized to a LD 12:12 illumination schedule (light from 0800 hr to 2000 hr) and fed ad libitum. The acrophase of the circadian rhythms in urinary GGT and LAP activity occurred at the end of the rest span of the animals: between 1730 and 1915 for GGT (depending on the mode of expression of the activity) and between 1700 and 1910 for LAP. Of striking resemblance in their timing, both these rhythms were also of large amplitude (about 50% of the mesor for urinary GGT activity and about 45% for LAP one). The circadian acrophases of urinary GGT and LAP activity led in timing the circadian rhythms in urine volume and creatinine excretion by about 13hr. Such findings consistent with the circadian variations found by other investigators in GGT in kidney homogenates or in LAP in human urine thus reflect a periodicity in renal tubular function. The reasons for these circadian variations, still unknown at this time, are discussed. The influence recently demonstrated of the hormonal context on protein and enzyme synthesis at the tubule, and its phase relations to urinary enzyme excretion emphasize how much the circadian rhythm in urinary GGT and LAP activity is well included in the murine time structure. Therefore it should be of interest to consider the circadian rhythm in urinary GGT and LAP release as a marker rhythm of predictive value as to the side effects of nephrotoxic drugs.     

Urinary excretion of lead and δ-aminolevulinic acid in workers occupationally exposed to tetraethyl lead

Forty-nine refinery workers and 50 motor mechanics were selected and examined for total lead (PbT), inorganic lead (PbI), and δ-aminolevulinic acid (ALA) in urine. The worker groups were exposed to tetraethyl lead (TEL) mainly by inhalation, but motor mechanics received additional exposure by skin because of hand cleansing with gasoline. The levels of urinary ALA (ALA-U) and urinary PbT (PbT-U) in refinery workers and motor mechanics were found to be significantly higher than the control group (p<0.05). The correlation between the ALA-U and PbT-U was found significant in both worker groups (p<0.001); however, relatively higher positive correlation was found between ALA-U and urinary inorganic lead (PbI-U) in TEL-exposed workers.     

Circadian Rhythm in Gamma Glutamyltranspeptidase and Leucine Aminopeptidase Urinary Activity in Rats

Urinary gamma glutamyltranspeptidase (GGT) and leucine aminopeptidase (LAP), renal tubular brush border enzymes, have been shown to be sensitive indicators of renal tubular functions. This study documents circadian rhythms in the urinary activity of GGT and LAP, statistically validated and quantified by the cosinor method, in 15 male Wistar rats standardized to a LD 12:12 illumination schedule (light from 0800 hr to 2000 hr) and fed ad libitum. The acrophase of the circadian rhythms in urinary GGT and LAP activity occurred at the end of the rest span of the animals: between 1730 and 1915 for GGT (depending on the mode of expression of the activity) and between 1700 and 1910 for LAP. Of striking resemblance in their timing, both these rhythms were also of large amplitude (about 50% of the mesor for urinary GGT activity and about 45% for LAP one). The circadian acrophases of urinary GGT and LAP activity led in timing the circadian rhythms in urine volume and creatinine excretion by about 13hr. Such findings consistent with the circadian variations found by other investigators in GGT in kidney homogenates or in LAP in human urine thus reflect a periodicity in renal tubular function. The reasons for these circadian variations, still unknown at this time, are discussed. The influence recently demonstrated of the hormonal context on protein and enzyme synthesis at the tubule, and its phase relations to urinary enzyme excretion emphasize how much the circadian rhythm in urinary GGT and LAP activity is well included in the murine time structure. Therefore it should be of interest to consider the circadian rhythm in urinary GGT and LAP release as a marker rhythm of predictive value as to the side effects of nephrotoxic drugs.     

Urinary excretion of immunoreactive prostaglandin E: A circadian rhythm and the effect of posture

The excretion of urinary immunoreactive prostaglandin E (iPGE), sodium, potassium, creatinine and volume was studied in 4 hr collections in normal women at normal activity. iPGE exhibited a circadian rhythm with an amplitude of 29% and peak excretion at 4:55 P.M. There were also significant circadian rhythms for sodium, potassium, creatinine, and volume, all peaking in late afternoon. There were no significant changes either in the total excretion or in the circadian rhythms of iPGE, potassium, or creatinine excretion when the subjects remained in bed for an entire day while the circadian rhythms of sodium and volume were significantly modified in amplitude and phase, respectively. Urinary aldosterone excretion decreased significantly when the subjects were at bed rest. iPGE excretion increased 33% when subjects were first recumbent and then erect for consecutive 4 hr periods on the same day (but when subjects were erect 1 day for a 4 hr period, iPGE excretion was lower by 32% than for the same 4 hr period the preceding day when they were recumbent). These data indicate that: 1) the sympathetic nervous system and renin-angiotensin-aldosterone system do not affect the circadian rhythm of urinary iPGE, and 2) short-term experiments of prostaglandin E excretion must be designed to avoid misleading results due to the circadian rhythm.     

Tumour-localizing properties of porphyrins. In vivo studies using free and liposome encapsulated aminolevulinic acid.

1. Using different doses of free and liposome encapsulated aminolevulinic acid (ALA) (between 2 and 8 mg/animal), given i.p., s.c. and intra-tumoural (i.t.), in vivo porphyrin synthesis by tumour, red blood cells (RBC) and different organs from tumour-bearing mice (TBM) and normal mice (NM) at different times, up to 24 hr after ALA administration, was examined. 2. It was found that by giving entrapped ALA, at a dose of 6 mg/animal (or 200 mg/kg wt), after 10 hr, a high level of porphyrin accumulation in the tumour was produced (7 micrograms/g tissue). Low synthesis occurred in muscle, lung, brain, RBC and skin; in spleen, kidney and liver synthesis is significant after 10 hr, but after 24 hr returned to normal values in the spleen and to about 2-3 micrograms/g tissue in the kidney and liver. 3. The tumour/skin porphyrin concentration ratio after 10 hr was nearly 30, the highest so far reported. 4. These results support our previous in vitro findings, indicating that free or encapsulated ALA might be used for early diagnosis of cancer and in photodynamic therapy.     

Urinary corticosteroid excretion patterns in the okapi (Okapia johnstoni)

Stress is known to alter a variety of biological processes, including behavior and reproduction. It is therefore important to understand the stress levels of animals in captivity, especially those for whom captive breeding is a priority, such as the okapi. Levels of stress hormones can be measured from samples collected noninvasively, such as urine or feces, which are preferable with nondomestic species for whom drawing blood might in itself be a considerable stressor. To understand the excretion of cortisol in urine in the okapi, four (1.3) animals were subject to three injections: saline, 200 IU of an adrenocorticotropic hormone (ACTH) analogue, and 300 IU of the analogue. Their 24‐hr urinary corticosteroid levels were compared with 4 baseline days. Injection with the ACTH analogue significantly increased the urinary corticosteroid levels compared with saline injections and baseline. Eight (3.5) okapi were then observed for 24 hr per day for 5 days to determine their normal patterns of corticosteroid production. The mean corticosteroid levels varied significantly by individual. A significant circadian pattern in urinary corticosteroid was apparent independent of individual or gender, with cortisol rising during the daylight hours and decreasing again at night. Zoo Biol 27:381–393, 2008. © 2008 Wiley‐Liss, Inc.     

Studies on the induction of -aminolevulinic acid synthetase iun mouse liver

Administration of 3,5-diethoxy carbonyl-1,4-dihydrocollidine (DDC) to mice resulted in a striking increase in the level of δ-aminolevulinic acid (ALA) synthetase in liver. Although the enzyme activity was primarily localized in mitochondria and postmicrosomal supernatant fluid, a significant level of activity was also detected in purified nuclei. The time course of induction showed a close parallelism between the bound and free enzyme activities with the former always accounting for a higher percentage of the total activity as compared to the latter. Studies with cycloheximide indicated a half-life of around 3 hr for both the bound and free ALA synthetase. Actinomycin D and hemin prevented enzyme induction when administered along with DDC, but when administered 12 hr after DDC treatment Actinomycin D did not lead to a decay of either the bound or free enzyme activity and hemin inhibited the bound enzyme activity but not the free enzyme level. The molecular sizes of the mitochondrial and cytosolic ALA synthetase(s) were found to be similar on sephadex columns.     

Circadian variations in plasma growth hormone and prolactin in the infant rat: Comparison with the adult pattern

Radioimmunoassayable (RIA) plasma growth hormone (GH) and prolactin (PRL) levels were determined at 3 hr intervals during a controlled 24-hr light-dark cycle in 10-day-old male and female rats; parallel measurements were made of brain monoamines (MA's), dopamine (DA), norepinephrine (NE) and serotonin (5-HT) concentration. Plasma GH and PRL and brain MA levels found in infant rats were compared to the same determinations made during the 24-hr cycle in 50-day-old male rats. GH levels were rather uniform and did not show circadian periodicity in the plasma of infant rats, while PRL levels showed a diurnal surge in the late afternoon hr (1800). In adult rats, GH levels exhibited wide fluctuations during the 24-hr cycle and no circadian periodicity, while PRL levels showed one diurnal (1500–1800) and one nocturnal (2400) surge. A pulsatile GH secretion was found in adult rats sampled at 15 min intervals over a period of 2 hr, which seemed to be lacking in infant rats. In the brain of infant rats, DA and NE levels exhibited circadian patterns which resembled the ones present in the brain of adult rats, whereas no circadian variations were present in 5-HT levels.     

Chronobiological Aspects of Weight Loss in Obesity: Effects of Different Meal Timing Regimens

A series of short- and long-lasting experimental protocols of different meal timing regimes were performed in obese subjects to assess the possible occurrence of (1) a different metabolic fate of nutrients; (2) a phase shift of circadian rhythms of metabolic and hormonal parameters strictly related to nutrition; (3) a different weight loss. (A) In a short-lasting protocol (3 days) IS obese subjects were fed a hypocaloric diet (684 kcal/day) (a) at 10 hr only, (b) at 1800 hr only; (c) at 1000 hr, 1400 hr and 1800 hr, or (d) studied during a 36-hr fasting. Measures of calorimetry (R.Q., CHO and lipid oxidations, energy expenditure), hormones (plasma Cortisol, insulin, HGH, urinary catecholamines), urinary electrolytes (Na, K) and vital parameters (body temperature, heart rate, blood pressure) were carried out at 4-hr intervals for three days. A significantly higher lipid oxidation and a lower CHO oxidation were documented with the meal at 1800 hr, in comparison with the meal at 1000 hr. CHO and lipid oxidation circadian rhythms appeared the most affected by meal timing. (B) In a long-lasting protocol (18 days) 10 obese subjects were fed the same hypocaloric diet (a) at 1000 hr only and (b) at 1800 hr only. Calorimetric measures were performed every other day for 2 hr preceding each meal. Before and after the 18-days single meal period, body temperature, plasma Cortisol, PRL and TSH were recorded (δt = 4 hr). A higher lipid oxidation and a lower CHO oxidation were again demonstrated with the meal at 18 hr. Minimal changes of hormonal circadian rhythms were documented suggesting that the hypothalamus-hypophysis network is scarcely affected by meal timing. Weight loss did not vary in both short- and long-term protocol.     

Biochemical characterization of porphobilinogen deaminase-deficient mice during phenobarbital induction of heme synthesis and the effect of enzyme replacement

Acute intermittent porphyria (AIP) is a genetic disorder caused by a deficiency of porphobilinogen deaminase (PBGD), the 3rd enzyme in heme synthesis. It is clinically characterized by acute attacks of neuropsychiatric symptoms and biochemically by increased urinary excretion of the porphyrin precursors porphobilinogen (PBG) and 5-aminolevulinic acid (ALA). A mouse model that is partially deficient in PBGD and biochemically mimics AIP after induction of the hepatic ALA synthase by phenobarbital was used in this study to identify the site of formation of the presumably toxic porphyrin precursors and study the effect of enzyme-replacement therapy by using recombinant human PBGD (rhPBGD). After 4 d of phenobarbital administration, high levels of PBG and ALA were found in liver, kidney, plasma, and urine of the PBGD-deficient mice. The administration of rhPBGD intravenously or subcutaneously after a 4-d phenobarbital induction was shown to lower the PBG level in plasma in a dose-dependent manner with maximal effect seen after 30 min and 2 h, respectively. Injection of rhPBGD subcutaneously twice daily during a 4-d phenobarbital induction reduced urinary PBG excretion to 25% of the levels found in PBGD-deficient mice administered with only phenobarbital. This study points to the liver as the main producer of PBG and ALA in the phenobarbital-induced PBGD-deficient mice and demonstrates efficient removal of accumulated PBG in plasma and urine by enzyme-replacement therapy.     

Sleep and Circadian Rhythms of Temperature and Urinary Excretion on a 22.8 hr “Day”

Two groups of subjects (total N = 6) were studied in an isolation chamber for a period of 3 weeks whilst living on a 22.8 hr “day”. Regular samples of urine were taken when the subjects were awake, deep body temperature was recorded continuously and polygraphic EEG recordings were made of alternate sleeps. The excretion in the urine of potassium, sodium, phosphate, calcium and a metabolite of melatonin were estimated.

Measurements of the quantity and quality of sleep were made together with assessments of the temperature profiles associated with sleep. In addition, cosinor analysis of circadian rhythmicity in urinary variables and temperature was performed.

The 22.8 hr “days” affected variables and subjects differently. These differences were interpreted as indicating that the endogenous component of half the subjects adjusted to the 22.8 hr “days” but that, for the other three, adjustment did not occur. When the behaviour of different variables was considered then some (including urinary potassium and melatonin, sleep length and REM sleep) appeared to possess a larger endogenous component than others (for example, urinary sodium, phosphate and calcium), with rectal temperature behaving in an intermediate manner. In addition, a comparison between different rhythms in any subject enabled inferences to be drawn regarding any links (or lack of them) that might exist between the rhythms. In this respect also, there was a considerable range in the results and no links between any of the rhythms appeared to exist in the group of subjects as a whole.

Two further groups (total N=8) were treated similarly except that the chamber clock ran at the correct rate. In these subjects, circadian rhythms of urinary excretion and deep body temperature (sleep stages and urinary melatonin were not measured) gave no evidence for deterioration. We conclude, therefore, that the results on the 22.8 hr “day” were directly due to the abnormal “day” length rather than to a prolonged stay in the isolation chamber.     

Ultradian, circadian and seasonal variations of plasma progesterone and LH concentrations during the luteal phase

The circadian variations in plasma progesterone (P) and LH concentrations were investigated in six women, aged 23-40 years. All were studied in the mid-luteal phase (7 +/- 2 days after LH mid-cycle surge). Experiments were conducted in autumn and in spring. Blood samples were obtained every 15 min for 24 hr. Plasma P and LH concentrations were measured by RIA. Each subject's time-series was analysed using three methods; visual inspection (chronogram), spectral analysis to estimate component periods of rhythms (tau) and cosinor analysis to quantify the rhythms parameters. Marked temporal variations in plasma P concentration were observed in each subject. The maximal variations over a 24-hr period, ranged between 13-58.5 mmol/l. Differences related to sampling time were statistically validated by ANOVA (p less than 0.00001). Significant harmonic periods were detected by spectral analysis but differed among subjects. In all subjects but one, a circadian rhythm was detected. The acrophase location was similar (about 0700 hr) in the four subjects studied in autumn, but ranged from 1940 to 0320 hr in those studied in spring. An ultradian rhythm with tau = 8 hr was also validated in six time-series with similar acrophases (about 0200, 1000, and 1800 hr). Cosinor analysis of pooled data revealed that the 24-hr, 12-hr, and 8-hr rhythms were statistically significant (p = 0.001) in autumn. algebraic sum of these three cosine functions yielded a circadian waveform with peak-times occurring near 0300 and 1130 hr and a trough-time about 2200 hr. In spring, the circadian pattern appeared quite different, and peak-times were found near 0700 and 2000 hr, and trough-times near 0300 and 1500 hr. Furthermore, the 24-hr mean of P was higher in autumn (28.9 +/- 0.4 nmol/l) than in spring (17.2 +/- 0.4 nmol/l), p from ANOVA less than 0.00001. The evidence for a similar circadian LH pattern is not as strong. Seasonal, circadian and ultradian rhythms characterize the physiologic time structure of plasma P concentration in mid-luteal phase.     

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.     

Circadian variations of vasopressin level and vasopressin-converting aminopeptidase activity in the rat pineal gland

Vasopressin levels and vasopressin-converting aminopeptidase activity were measured in the rat pineal gland during the 24 hr light-dark cycle. A rhythmic variation in peptide levels and peptidase activity occurred. At the onset of light at 6.00 hr, the peptidase displayed a significant, short-lasting (approximately 3 hr) increase of about 35% in activity, while a decrease of 28% in pineal vasopressin levels was observed. The changes in peptidase activity and peptide level were not triggered by light per se, since they persisted to occur at the same time point in animals which were not exposed to light, indicating the circadian nature of the rhythmicity. These changes were specific to the pineal gland, since other tissues, like hippocampus and pituitary gland, did not show these daily variations. The data suggest a relationship between vasopressin levels and vasopressin-converting aminopeptidase activity.     

Circadian rhythms of urinary excretions of water and electrolytes in patients receiving total parenteral nutrition (TPN)

In order to determine whether the usual feeding pattern actually modifies the circadian rhythms of urinary excretion of water and electrolytes, we compared the circadian rhythm characteristics in patients receiving total parenteral nutrition (TPN group) with those in patients on an ordinary hospital diet (control group). Statistically significant circadian rhythms were detected in all of the urinary variables investigated herein by using the population mean-cosinor method in both groups. In addition, there were no statistically significant differences of the mesor, the %-amplitude and the acrophase between the two groups. These results suggest that the usual feeding pattern is not a main determinant in forming the circadian rhythm characteristics of human urinary variables.     

Sex differences in the circadian profiles of melatonin and cortisol in plasma and urine matrices under constant routine conditions

Conflicting evidence exists as to whether there are differences between males and females in circadian timing. The aim of the current study was to assess whether sex differences are present in the circadian regulation of melatonin and cortisol in plasma and urine matrices during a constant routine protocol. Thirty-two healthy individuals (16 females taking the oral contraceptive pill (OCP)), aged 23.8 ± 3.7 (mean ± SD) years, participated. Blood (hourly) and urine (4-hourly) samples were collected for measurement of plasma melatonin and cortisol, and urinary 6-sulfatoxymelatonin (aMT6s) and cortisol, respectively. Data from 28 individuals (14 females) showed no significant differences in the timing of plasma and urinary circadian phase markers between sexes. Females, however, exhibited significantly greater levels of plasma melatonin and cortisol than males (AUC melatonin: 937 ± 104 (mean ± SEM) vs. 642 ± 47 pg/ml.h; AUC cortisol: 13581 ± 1313 vs. 7340 ± 368 mmol/L.h). Females also exhibited a significantly higher amplitude rhythm in both hormones (melatonin: 43.8 ± 5.8 vs. 29.9 ± 2.3 pg/ml; cortisol: 241.7 ± 23.1 vs. 161.8 ± 15.9 mmol/L). Males excreted significantly more urinary cortisol than females during the CR (519.5 ± 63.8 vs. 349.2 ± 39.3 mol) but aMT6s levels did not differ between sexes. It was not possible to distinguish whether the elevated plasma melatonin and cortisol levels observed in females resulted from innate sex differences or the OCP affecting the synthetic and metabolic pathways of these hormones. The fact that the sex differences observed in total plasma concentrations for melatonin and cortisol were not reproduced in the urinary markers challenges their use as a proxy for plasma levels in circadian research, especially in OCP users.     

Letter from the President: Expectations and Needs of Members of the International Society of Chronobiology

The focus of the reported work is investigation of disopyramide chronopharmacokinetics in the mouse. Different groups of male NMRI mice maintained under controlled environmental conditions (LD: 0600-1800) received a single intraperitoneal injection of disopyramide (30mg per kg of body weight) at one of four different fixed time points of a 24-h period, i.e. 1000, 1600, 2200 or 0400. Blood samples were taken 0.5,1,2,3,4 and 6 hr after drug administration and total and free plasma levels of disopyramide were measured by an immunoenzymatic method.

Our data showed statistically significant circadian rhythms in the following pharmacokinetic parameters: highest volume of distribution = 3.91 ± 0.211kg^?1 at 2200 (circadian amplitude, half the peak-to-trough difference relative to the 24-hr mean multiplied by 100, is 34%); highest area under concentration curves = 16.06 ± 1.03μgml^?1hr^?1 at 0400 (circadian amplitude = 43%) and highest clearance = 3.04 ± 0.191hr“kg”¹ at 2200 (circadian amplitude = 21%). Protein binding of the drug was shown to ^he circadian time dependent. Alpha and beta phase elimination half-lives were not found to be significantly circadian phase-dependent. Thus circadian changes in disopyramide clearance may represent circadian changes in the drug's volume of distribution.     

Circadian Rhythm of Hepatic Cytosolic and Nuclear Estrogen Receptors

The distribution of estrogen receptor between the cytosolic and nuclear compartments were evaluated in liver of male rats to determine whether a circadian rhythm exists. Cytosolic receptor reached a maximum level at 400 hours and a minimum at 2000 and 2400 hr. Nuclear receptor reached a maximum level at 800 hr and was lowest at 1600 and 2000 hr. Serum estradiol levels were also highest at 800 hr and lowest at 1600 hr. The variations in cytosolic and nuclear receptors are not reciprocal; in fact, the overall content of receptor in the liver is not constant and also displays a circadian rhythm.