- Email: [email protected]
Markers of urine tampering—detection of sample tampering in an opiate dependency program
9TH INTERNATIONAL/6TH EUROPEAN JOINT SYMPOSIUM ON PURINE AND PYRIMIDINE METABOLISM IN MAN 20% TCA solution removed detectable levels of proteins, and did not affect the measurement of uric acid. Second, protein-free supernatants from IgM containing samples were measured by the OM and compared with the corresponding serum samples measured by the MM. There was good correlation between the two methods (r = 0.945), and no statistical difference between the means using a paired t-test. Conclusion The modified method is satisfactory for routine analysis of samples, including those with IgM paraproteins.
Results Over 200 samples were compared visually and spectrophotometrically. Seventy CSF samples were assessed quantitatively. Forty two samples had no measurable bilirubin; in 25 CSF bilirubin concentrations were <0.45 umol/L. The three samples with bilirubin concentrations of 0.45 umol/L or greater were visually xanthochromatic. Conclusions Spectrophotometric assessment has the advantage of objectivity but to date has not confirmed additional SAH. Clinical evaluation and comparison studies are continuing.
TOXICOLOGY AND DRUGS OF ABUSE 40. 38.
MONITORING INTRAVENOUS LIPID INFUSIONS IN NEONATES: TRIGLYCERIDES VS TURBIDITY
Halstead, A.C. 1, Ling, E.W. 2, Albersheim, S.G. 2, and Tsai, M. 1, Departments of Pathology 1 and Pediatrics 2, B.C.'s Children's Hospital, 4480 Oak St., Vancouver, B.C. V6H 3V4, Canada
Young Tai, KF. W. and Collier, C.P., Dept. of Paediatrics and Pathology, Queen's University and Kingston General Hospital, 76 Stuart St., Kingston, Ont., K7L 2V7, Canada Objectives As most of the studies on measuring turbidity for this purpose were done 20 years ago, we have revisited the correlation between triglycerides (TRIG) and turbidity (TBD); and have performed an informal survey of current practises in laboratories that service neonatal intensive care units. Methods For 6 months in 1996, we analysed TBD (by spectrophotometry, 600 nm) and TRIG (PARAMAX, not blanked for glycerol) in 312 samples from 55 neonates receiving total parenteral nutrition (5-10% glucose, Vamin amino acid solution and 20% Intralipid) as a constant 24 hour infusion. The survey was sent by FAX in Canada, and by listserv (ACB, UK) internationally. Results Both the TRIG (0.6-2.3 mM) and the TBD (<1.2 g/L) results were normal in 289 samples; 7 had both results elevated; 7 had elevated TRIGs only; and 9 had elevated TBDs only. No clinical cause (eg. infection) was identified for the discordant results. Serum TBD was quantified in 3/6 labs in Canada (2 by spectrophotometry, 1 by nephelometry); but not in any of the 6 labs outside Canada. TBD was estimated visually by 3 labs (one in Canada; 2 internationally). Conclusions TRIG and TBD results correlated 95% of the time using our current methodologies. TBD was measured by only 50% of surveyed labs (6/12): this test, and its literature, needs to be reviewed based on today's clinical protocols and laboratory procedures.
39.
XANTHOCHROMIA: VISUAL OR SPECTROPHOTOMETRIC A S S E S S M E N T Tesanovic, M~ Gibb, AP., Croft, J., Sutherland, G., and Haydon, C., Calgary Laboratory Services, Foothills Hospital, Calgary, Alberta T2N 2T9
Timely diagnosis of sub-arachnoid hemorrhage (SAH) is of utmost importance for patient management and outcome. A negative CT scan is followed by lumbar puncture in patients with history of suspected SAH. Yellow coloration or xanthochromia of cerebrospinal fluid (CSF) may indicate hemoglobin and/or bilirubin. Objectives To compare visual/spectrophotometric assessment and to investigate whether the latter is a more sensitive and specific test for detection of SAH. Methods After centrifugation the CSF were visually examined for xanthochromia. The same specimens were scanned at 350-700 nm and evaluated for the presence of hemoglobin, ilirubin and other chromogens. Absorbances, delta absorbance and derivative spectras were recorded and used for quantitation as needed. 378
MECONIUM TESTING FOR DIAGNOSIS OF INTRA-UTERINE COCAINE OR OPIATE EXPOSURE
Detection of drug use in pregnancy is important for management of mother and newborn. Meconium, which forms after 16 weeks pregnancy, has been proposed as a good sample to test for drugs. Objective To evaluate radio immunoassay (RIA) screening for cocaine and morphine in meconium, followed by gas chromatography/mass spectrometry (GC/MS) confirmation, as a technique for detecting intra-uterine drug exposure. Methods Meconium was collected from three groups of infants: a) 27 infants of non-drug using mothers and 25 infants of mothers reporting drug use in pregnancy, b) 519 randomly selected infants and c) 467 infants whose mothers consented to provide information about drug use during pregnancy. RIA for cocaine metabolite and serum morphine (Coat-A-Count, DPC) was performed as previously reported (Clin Biochem 1995; 28:335). Samples with cocaine metabolite reactivity 50 ng/g or morphine reactivity 20 ng/g were analysed by GC/MS (Riverview Hospital). GC/MS detected cocaine, benzoyl ecgonine, codeine and morphine 5 ng/g meconium. Results In group a), RIA identified 19/25 samples for cocaine and 9/25 for morphine confirmation. GC/MS confirmed 65% of cocaine and all the morphine "positives". In randomly screened infants RIA detected cocaine in 35 (6.7% and morphine in 20 (3.9%). GC/MS confirmed 3/25 (12%) cocaine and 9/17 (53%) morphine samples with sufficient meconium. In the consenting group, of 16 cocaine and 6 morphine "positives" by RIA, GC/MS confirmed 1/12 (8%) cocaine and 5/6 (83%) morphine samples. Conclusions RIA followed by GC/MS identified intra-uterine opiate exposure. The low confirmation rate for cocaine, however, suggests that specificity of the RIA method and development of GC/MS methods for other cocaine metabolites must be investigated before reliable meconium screening for cocaine can be implemented.
41.
MARKERS OF URINE T A M P E R I N G - - D E T E C TION OF SAMPLE TAMPERING IN AN OPIATE DEPENDENCY PROGRAM Kapur, B. M, Hershkop, S. and Koren, G. Div. of Clin. Pharm. and Toxicology, The Hospital for Sick Children, 555 University Ave, Toronto ON. M5G 1X8 Canada; The Depts. Of Clinical Biochemistry and Pharmacology, University of Toronto, and Daniel Medical Laboratories (MedChem Laboratories).
Patients are known to add adulterants or may resubmit urine samples to avoid detection of drug use. We report here a reevalCLINICAL BIOCHEMISTRY, VOLUME 30, J U N E 1997
POSTER ABSTRACTS uation of the different analytes used as markers of adulteration and the development of a reference range for sample tampering. We also investigated the possibility of using the same lab results in the development of a unique fingerprint to identify a resubmitted sample. Method Urine creatinine and specific gravity were done on 266 urine samples (88 males & 178 females). 3500 urine samples submitted for drug analysis and Na, C1, pH and Cr. were used to develop reference ranges. A computer algorithm was developed using these results to generate a unique fingerprint of the sample. Results For any given value of SpGr we found a wide range of values for Cr. Reference ranges based on our sample size of 3500 are as follows: sodium, 20-250 mmol/L; chloride, 15-275 mmol/L; pH, 5.0-8.0 and Cr., 2.0 mmol/L respectively. These ranges exclude the lower and upper 2.5% of our population. Using the reference ranges and the computer algorithm, we were able to identify many patients who had either diluted the sample, or caused a pH change or had resubmitted the urine sample. In one incidence three patients had submitted the same urine sample. All acknowledged resubmission when confronted. Methadone was usually not detectable in urine samples with high pH although there was evidence the patient took the medication. Conclusions Urine Cr. may be more sensitive than SpGr as a marker than of dilution. Resubmission occurs frequently and can be detected using the algorithm we have developed.
42.
OXAPROZIN CROSS-REACTIVITY IN THE ABBOTT F P I A BENZODIAZEPINE ASSAY Fraser, A. D. and Howell, P., Division of Clinical Chemistry, Queen Elizabeth II Health Sciences Centre, 1278 Tower Road, Halifax, Nova Scotia, B3H 2Y9, Canada
Immunoassay methods are commonly used to test for several drug classes as part of urine drug screening programmes. Oxaprozin (Daypro ®) is a new drug which has been reported to cross-react in immunoassay methods for benzodiazepines. Objectives To characterize the immunoreactivity of oxaprozin standards over a wide concentration range when analyzed by FPIA with the Abbott TDx FLx assay for benzodiazepines in urine. The second objective was to analyze urine specimens by FPIA from human subjects following single oral doses of oxaprozin. Methods Oxaprozin pure standard was obtained from Searle Pharmaceutical Co. Oxaprozin standards were prepared in drug free urine at concentrations from 500-100,000 ng/mL. After taking a 1200 mg oral dose of oxaprozin, urine specimens were collected from 12 subjects up to 72 hours post-dose. The urine specimens were analyzed by the FPIA procedure using a cut-off of 200 ng/mL (as nordiazepam equivalents). Results Oxaprozin standards at 10,000 ng/mL and higher gave presumptive positive benzodiazepine results by FPIA. In all 12 subjects, each urine collection (0-24, 24-48, and 48-72h postdose) gave positive benzodiazepine results by FPIA. Conclusion Presumptive positive immunoassay screening tests for benzodiazepines by FPIA may be due to the presence of other drugs such as the anti-inflammatory drug oxaprozin (Daypro®). It is recommended that all presumptive positive benzodiazepine screening results be confirmed by another technique based upon a different principle of analysis. CLINICAL BIOCHEMISTRY, VOLUME 30, J U N E 1997
MOLECULAR 43.
BIOLOGY AND DNA PROBES
EFFECT OF ATORVASTATIN ON THE INTRACELLULAR TRANSLOCATION AND DEGRADATION OF APOB IN HEPG2 CELLS Mohammadi, A.*, Macri, J.*, Newton R., and Adeli, K.*, Department of Chemistry and Biochemistry*, University of Windsor, Windsor, Ontario, Canada, N9B 3P4, and ParkeDavis Pharmaceutical Research, Warner-Lambert Co., Ann Arbor, MI, USA
Statins are a family of HMG-CoA reductase inhibitors that effectively lower the LDL-cholesterol levels in people susceptible to atherosclerosis. Objectives We investigated the effect of atorvastatin, a new HMG-CoA reductase inhibitor, on the biogenesis of apoB in human hepatocytes (HepG2 cells). We studied the effect of atorvastatin on: 1) intracellular degradation of apoB, 2) translocation of apoB into the lumen of the endoplasmic reticulum (ER), 3) assembly of apoB containing lipoproteins in the ER lumen, and 4) secretion of apoB in the culture medium. Methods HepG2 cells were treated with atorvastatin. The cells were then pulsed with [~SS]methionine, and in some cases permeabilized with digitonin. ApoB degradation was measured by comparing the amount of apoB recovered in control and atorvastatin treated cells after a 2h chase period. The rate of apoB translocation into the ER was determined by permeabilizing and treating the cells with trypsin, following the pulse and chase period. Secretion of apoB was simply measured by immunoprecipitation of apoB from the medium, following the appropriate chase period. Results Atorvastatin enhanced degradation of apoB, and decreased apoB translocation into the ER of HepG2 cells. The net effect of atorvastatin was a reduction in the number of apoB containing lipoproteins of different sizes in the ER lumen and a reduction in apoB secretion in the culture medium. Conclusion The results suggest that atorvastatin impairs the translocation of apoB into the lumen of the ER and also increases the amount of apoB degraded intracellularly. It is hypothesized that atorvastatin alters these parameters primarily as a result of inhibiting cholesterol synthesis and limiting the availability of cholesterol for the normal assembly of cholesterol and cholesterol esters into the lipoprotein particles.
44.
EFFECTS OF THE IMMUNOSUPRESSIVE AGENT CYCLOSPORIN A ON THE PRODUCTION OF APOLIPOPROTEIN B CONTAINING LIPOPROTEINS Macri, J., Thibert, R.J., and Adeli, K., Dept. of Chemistry and Biochemistry, University of Windsor, Windsor, Ontario, N9B 3P4
Atherosclerosis is a leading cause of death in long-term survivors of heart as well as renal transplantation. Posttransplant hyperlipidemia has been suggested to exacerbate this disease state. Immunosuppresive agents which are used to prevent the rejection of transplanted organs have been shown to adversely alter lipoprotein metabolism. Treatment with the immunosuppresive drug cyclosporin A (CsA) has been demonstrated to significantly increase low-density lipoprotein cholesterol and apolipoprotein B (apoB) plasma levels. Objectives The present study was conducted to determine if these observed increases are a function of increased hepatic production of apoB-containing lipoproteins. The effect of CsA on the secretion of apoB-containing lipoproteins from HepG2 cells was studied. In addition, the effects of the immunosuppresive reagent on the major regulatory mechanisms involved in apoB production, intra379
Results Over 200 samples were compared visually and spectrophotometrically. Seventy CSF samples were assessed quantitatively. Forty two samples had no measurable bilirubin; in 25 CSF bilirubin concentrations were <0.45 umol/L. The three samples with bilirubin concentrations of 0.45 umol/L or greater were visually xanthochromatic. Conclusions Spectrophotometric assessment has the advantage of objectivity but to date has not confirmed additional SAH. Clinical evaluation and comparison studies are continuing.
TOXICOLOGY AND DRUGS OF ABUSE 40. 38.
MONITORING INTRAVENOUS LIPID INFUSIONS IN NEONATES: TRIGLYCERIDES VS TURBIDITY
Halstead, A.C. 1, Ling, E.W. 2, Albersheim, S.G. 2, and Tsai, M. 1, Departments of Pathology 1 and Pediatrics 2, B.C.'s Children's Hospital, 4480 Oak St., Vancouver, B.C. V6H 3V4, Canada
Young Tai, KF. W. and Collier, C.P., Dept. of Paediatrics and Pathology, Queen's University and Kingston General Hospital, 76 Stuart St., Kingston, Ont., K7L 2V7, Canada Objectives As most of the studies on measuring turbidity for this purpose were done 20 years ago, we have revisited the correlation between triglycerides (TRIG) and turbidity (TBD); and have performed an informal survey of current practises in laboratories that service neonatal intensive care units. Methods For 6 months in 1996, we analysed TBD (by spectrophotometry, 600 nm) and TRIG (PARAMAX, not blanked for glycerol) in 312 samples from 55 neonates receiving total parenteral nutrition (5-10% glucose, Vamin amino acid solution and 20% Intralipid) as a constant 24 hour infusion. The survey was sent by FAX in Canada, and by listserv (ACB, UK) internationally. Results Both the TRIG (0.6-2.3 mM) and the TBD (<1.2 g/L) results were normal in 289 samples; 7 had both results elevated; 7 had elevated TRIGs only; and 9 had elevated TBDs only. No clinical cause (eg. infection) was identified for the discordant results. Serum TBD was quantified in 3/6 labs in Canada (2 by spectrophotometry, 1 by nephelometry); but not in any of the 6 labs outside Canada. TBD was estimated visually by 3 labs (one in Canada; 2 internationally). Conclusions TRIG and TBD results correlated 95% of the time using our current methodologies. TBD was measured by only 50% of surveyed labs (6/12): this test, and its literature, needs to be reviewed based on today's clinical protocols and laboratory procedures.
39.
XANTHOCHROMIA: VISUAL OR SPECTROPHOTOMETRIC A S S E S S M E N T Tesanovic, M~ Gibb, AP., Croft, J., Sutherland, G., and Haydon, C., Calgary Laboratory Services, Foothills Hospital, Calgary, Alberta T2N 2T9
Timely diagnosis of sub-arachnoid hemorrhage (SAH) is of utmost importance for patient management and outcome. A negative CT scan is followed by lumbar puncture in patients with history of suspected SAH. Yellow coloration or xanthochromia of cerebrospinal fluid (CSF) may indicate hemoglobin and/or bilirubin. Objectives To compare visual/spectrophotometric assessment and to investigate whether the latter is a more sensitive and specific test for detection of SAH. Methods After centrifugation the CSF were visually examined for xanthochromia. The same specimens were scanned at 350-700 nm and evaluated for the presence of hemoglobin, ilirubin and other chromogens. Absorbances, delta absorbance and derivative spectras were recorded and used for quantitation as needed. 378
MECONIUM TESTING FOR DIAGNOSIS OF INTRA-UTERINE COCAINE OR OPIATE EXPOSURE
Detection of drug use in pregnancy is important for management of mother and newborn. Meconium, which forms after 16 weeks pregnancy, has been proposed as a good sample to test for drugs. Objective To evaluate radio immunoassay (RIA) screening for cocaine and morphine in meconium, followed by gas chromatography/mass spectrometry (GC/MS) confirmation, as a technique for detecting intra-uterine drug exposure. Methods Meconium was collected from three groups of infants: a) 27 infants of non-drug using mothers and 25 infants of mothers reporting drug use in pregnancy, b) 519 randomly selected infants and c) 467 infants whose mothers consented to provide information about drug use during pregnancy. RIA for cocaine metabolite and serum morphine (Coat-A-Count, DPC) was performed as previously reported (Clin Biochem 1995; 28:335). Samples with cocaine metabolite reactivity 50 ng/g or morphine reactivity 20 ng/g were analysed by GC/MS (Riverview Hospital). GC/MS detected cocaine, benzoyl ecgonine, codeine and morphine 5 ng/g meconium. Results In group a), RIA identified 19/25 samples for cocaine and 9/25 for morphine confirmation. GC/MS confirmed 65% of cocaine and all the morphine "positives". In randomly screened infants RIA detected cocaine in 35 (6.7% and morphine in 20 (3.9%). GC/MS confirmed 3/25 (12%) cocaine and 9/17 (53%) morphine samples with sufficient meconium. In the consenting group, of 16 cocaine and 6 morphine "positives" by RIA, GC/MS confirmed 1/12 (8%) cocaine and 5/6 (83%) morphine samples. Conclusions RIA followed by GC/MS identified intra-uterine opiate exposure. The low confirmation rate for cocaine, however, suggests that specificity of the RIA method and development of GC/MS methods for other cocaine metabolites must be investigated before reliable meconium screening for cocaine can be implemented.
41.
MARKERS OF URINE T A M P E R I N G - - D E T E C TION OF SAMPLE TAMPERING IN AN OPIATE DEPENDENCY PROGRAM Kapur, B. M, Hershkop, S. and Koren, G. Div. of Clin. Pharm. and Toxicology, The Hospital for Sick Children, 555 University Ave, Toronto ON. M5G 1X8 Canada; The Depts. Of Clinical Biochemistry and Pharmacology, University of Toronto, and Daniel Medical Laboratories (MedChem Laboratories).
Patients are known to add adulterants or may resubmit urine samples to avoid detection of drug use. We report here a reevalCLINICAL BIOCHEMISTRY, VOLUME 30, J U N E 1997
POSTER ABSTRACTS uation of the different analytes used as markers of adulteration and the development of a reference range for sample tampering. We also investigated the possibility of using the same lab results in the development of a unique fingerprint to identify a resubmitted sample. Method Urine creatinine and specific gravity were done on 266 urine samples (88 males & 178 females). 3500 urine samples submitted for drug analysis and Na, C1, pH and Cr. were used to develop reference ranges. A computer algorithm was developed using these results to generate a unique fingerprint of the sample. Results For any given value of SpGr we found a wide range of values for Cr. Reference ranges based on our sample size of 3500 are as follows: sodium, 20-250 mmol/L; chloride, 15-275 mmol/L; pH, 5.0-8.0 and Cr., 2.0 mmol/L respectively. These ranges exclude the lower and upper 2.5% of our population. Using the reference ranges and the computer algorithm, we were able to identify many patients who had either diluted the sample, or caused a pH change or had resubmitted the urine sample. In one incidence three patients had submitted the same urine sample. All acknowledged resubmission when confronted. Methadone was usually not detectable in urine samples with high pH although there was evidence the patient took the medication. Conclusions Urine Cr. may be more sensitive than SpGr as a marker than of dilution. Resubmission occurs frequently and can be detected using the algorithm we have developed.
42.
OXAPROZIN CROSS-REACTIVITY IN THE ABBOTT F P I A BENZODIAZEPINE ASSAY Fraser, A. D. and Howell, P., Division of Clinical Chemistry, Queen Elizabeth II Health Sciences Centre, 1278 Tower Road, Halifax, Nova Scotia, B3H 2Y9, Canada
Immunoassay methods are commonly used to test for several drug classes as part of urine drug screening programmes. Oxaprozin (Daypro ®) is a new drug which has been reported to cross-react in immunoassay methods for benzodiazepines. Objectives To characterize the immunoreactivity of oxaprozin standards over a wide concentration range when analyzed by FPIA with the Abbott TDx FLx assay for benzodiazepines in urine. The second objective was to analyze urine specimens by FPIA from human subjects following single oral doses of oxaprozin. Methods Oxaprozin pure standard was obtained from Searle Pharmaceutical Co. Oxaprozin standards were prepared in drug free urine at concentrations from 500-100,000 ng/mL. After taking a 1200 mg oral dose of oxaprozin, urine specimens were collected from 12 subjects up to 72 hours post-dose. The urine specimens were analyzed by the FPIA procedure using a cut-off of 200 ng/mL (as nordiazepam equivalents). Results Oxaprozin standards at 10,000 ng/mL and higher gave presumptive positive benzodiazepine results by FPIA. In all 12 subjects, each urine collection (0-24, 24-48, and 48-72h postdose) gave positive benzodiazepine results by FPIA. Conclusion Presumptive positive immunoassay screening tests for benzodiazepines by FPIA may be due to the presence of other drugs such as the anti-inflammatory drug oxaprozin (Daypro®). It is recommended that all presumptive positive benzodiazepine screening results be confirmed by another technique based upon a different principle of analysis. CLINICAL BIOCHEMISTRY, VOLUME 30, J U N E 1997
MOLECULAR 43.
BIOLOGY AND DNA PROBES
EFFECT OF ATORVASTATIN ON THE INTRACELLULAR TRANSLOCATION AND DEGRADATION OF APOB IN HEPG2 CELLS Mohammadi, A.*, Macri, J.*, Newton R., and Adeli, K.*, Department of Chemistry and Biochemistry*, University of Windsor, Windsor, Ontario, Canada, N9B 3P4, and ParkeDavis Pharmaceutical Research, Warner-Lambert Co., Ann Arbor, MI, USA
Statins are a family of HMG-CoA reductase inhibitors that effectively lower the LDL-cholesterol levels in people susceptible to atherosclerosis. Objectives We investigated the effect of atorvastatin, a new HMG-CoA reductase inhibitor, on the biogenesis of apoB in human hepatocytes (HepG2 cells). We studied the effect of atorvastatin on: 1) intracellular degradation of apoB, 2) translocation of apoB into the lumen of the endoplasmic reticulum (ER), 3) assembly of apoB containing lipoproteins in the ER lumen, and 4) secretion of apoB in the culture medium. Methods HepG2 cells were treated with atorvastatin. The cells were then pulsed with [~SS]methionine, and in some cases permeabilized with digitonin. ApoB degradation was measured by comparing the amount of apoB recovered in control and atorvastatin treated cells after a 2h chase period. The rate of apoB translocation into the ER was determined by permeabilizing and treating the cells with trypsin, following the pulse and chase period. Secretion of apoB was simply measured by immunoprecipitation of apoB from the medium, following the appropriate chase period. Results Atorvastatin enhanced degradation of apoB, and decreased apoB translocation into the ER of HepG2 cells. The net effect of atorvastatin was a reduction in the number of apoB containing lipoproteins of different sizes in the ER lumen and a reduction in apoB secretion in the culture medium. Conclusion The results suggest that atorvastatin impairs the translocation of apoB into the lumen of the ER and also increases the amount of apoB degraded intracellularly. It is hypothesized that atorvastatin alters these parameters primarily as a result of inhibiting cholesterol synthesis and limiting the availability of cholesterol for the normal assembly of cholesterol and cholesterol esters into the lipoprotein particles.
44.
EFFECTS OF THE IMMUNOSUPRESSIVE AGENT CYCLOSPORIN A ON THE PRODUCTION OF APOLIPOPROTEIN B CONTAINING LIPOPROTEINS Macri, J., Thibert, R.J., and Adeli, K., Dept. of Chemistry and Biochemistry, University of Windsor, Windsor, Ontario, N9B 3P4
Atherosclerosis is a leading cause of death in long-term survivors of heart as well as renal transplantation. Posttransplant hyperlipidemia has been suggested to exacerbate this disease state. Immunosuppresive agents which are used to prevent the rejection of transplanted organs have been shown to adversely alter lipoprotein metabolism. Treatment with the immunosuppresive drug cyclosporin A (CsA) has been demonstrated to significantly increase low-density lipoprotein cholesterol and apolipoprotein B (apoB) plasma levels. Objectives The present study was conducted to determine if these observed increases are a function of increased hepatic production of apoB-containing lipoproteins. The effect of CsA on the secretion of apoB-containing lipoproteins from HepG2 cells was studied. In addition, the effects of the immunosuppresive reagent on the major regulatory mechanisms involved in apoB production, intra379