Association of β2-adrenergic receptor (β2AR) haplotype and hypertension in African Americans and...
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PDII-A-8 HUMAN PHENYLETHANOLAMINE N-METHYLTRANS- FERASE (PNMT) PHARMACOGENETICS: GENE RESEQUENC- ING AND FUNCTIONAL GENOMIC STUDIES. Y. Ji, O. E. Salavaggione, MD, A. A. Adjei, PhD, B. A. Thomae, B. Eckloff, E. D. Wieben, PhD, R. M. Weinshilboum, MD, Mayo Clinic, Roches- ter, MN. PNMT (EC 2.1.1.28) catalyzes the N-methylation of norepineph- rine to form epinephrine. We set out to resequence the human PNMT gene, including all exons and introns as well as approximately 1 kb of the 5-flanking region using Coriell Institute DNA samples from 60 African-American (AA) and 60 Caucasian-American (CA) sub- jects. Within the 3.5 kb resequenced, 17 single nucleotide polymor- phisms (SNPs) were observed, including 3 nonsynonymous cSNPs (Asn9Ser, Thr98Ala and Arg112Cys). When constructs for the non- synonymous cSNPs were transiently expressed in COS-1 cells, the Ala98 allozyme displayed virtually no enzyme activity or immuno- reactive protein when compared with the wild type (WT) allozyme (P0.01), while values for the other variant allozymes did not differ significantly from those for WT. Rabbit reticulocyte lysate studies showed that the decrease in immunoreactive protein for the Ala98 allozyme was due–at least in part–to accelerated protein degradation. These observations raise the possibility of inherited variation in the ability to form epinephrine from norepinephrine. PDII-A-9 ASSOCIATION OF 2-ADRENERGIC RECEPTOR (2AR) HAPLOTYPE AND HYPERTENSION IN AFRICAN AMERI- CANS AND CAUCASIANS. B. S. Belgado, PharmD, L. H. Cav- allari, PharmD, T. Langaee, PhD, T. Okorochukwu, A. Sloan, MSC., J. Johnson, PharmD, University of Florida College of Pharmacy, University of Illinois at Chicago, College of Pharmacy, Gainesville, FL. The 2AR gene has been associated with hypertension, but data are conflicting. Racial differences in this association or role of the 2AR haplotype have not been well studied. We sought to determine whether race and/or haplotype influence the association between the 2AR gene and hypertension. Genetic samples were obtained from African American (AA) or Caucasian (C) hypertensive (HT) or normotensive (NT) patients. 2AR codon 16 and 27 genotypes were determined by PCR and luciferase-based pyrosequencing. Differ- ences were analyzed by Chi-square and Fisher’s exact test with AA and C analyzed separately. Haplotype frequencies were compared by race between NT and HT. A total of 482 patients were enrolled. Allele and genotype frequencies were similar for HT and NT at codons 16 and 27 for both AA and C. No differences were found in 2AR haplotypes between NT and HT for AA or C (Table). There were no differences in blood pressure across haplotype for NT AA or C. Our data do not support a significant contribution of the 2AR gene to hypertension risk. Table. Haplotype frequencies NT AA (%) HT AA (%) NT C(%) HT C(%) Arg16/Gln27 43 (48.9) 138 (48.9) 96 (38.1) 109 (38.4) Gly16/Gln27 33 (37.5) 90 (31.9) 59 (23.4) 57 (20.1) Gly16/Glu27 12 (13.6) 51 (18.1) 95 (37.7) 118 (41.5) Arg16/Glu27 0 (0) 3 (1.1) 2 (0.8) 0 (0) PDII-A-10 ALPHA-2B ADRENERGIC RECEPTOR (ADRA2B) 301-303 DELETION POLYMORPHISM AND VASCULAR DESENSITI- ZATION IN VIVO. M. Muszkat, MD, G. Sofowora, MD, H. Xie, MD, PhD, P. A. Harris, PhD, A. J. Wood, MD, C. Stein, MD, Vanderbilt University, Nashville, TN. Alpha-2 adrenergic receptors (ADRA2) play important roles in both central and peripheral regulation of vascular tone. The ADRA2B subtype mediates vasoconstriction and a common genetic variation, 301-303 deletion, was associated with loss of agonist-induced desen- sitization in vitro. Desensitization of vascular ADRA2 responses in vivo has not been previously described; nor is the effect of genetic variation known. We examined the hypothesis that 301-303del poly- morphism affects vascular desensitization to the selective ADRA2 agonist, dexmedetomidine (Dex) in vivo. Incremental doses of Dex (0.01–1000 ng/min) were infused into a dorsal hand vein (DHV) in 28 healthy subjects (age 18-45 years) and responses measured using a linear variable differential transformer. A dose-response curve was constructed and the ED50 calculated. On a separate day, the Dex dose that had caused at least 50% venoconstriction in the dose-response study was infused for three hours and response measured every 30 minutes. The area under the curve for DHV response normalized to the initial response (nAUC) was calculated. Genotyping for 301- 303del was performed, and relation to nAUC was determined. There was more than 3-fold inter-individual variability in nAUC. This was not related to ADRA2B genotype (p0.846). Inter-individual vari- ability in vascular responses to ADRA2 agonist over time occurs, but is not explained by the ADRA2B 301-303del. PDII-B-1 VITAMIN E FORMULATION AFFECTS DIGOXIN ABSORP- TION BY INHIBITING P-GLYCOPROTEIN (P-GP) IN HUMANS. L. Chan, PharmD, L. M. Humma, PharmD, C. A. Schriever, PharmD, MS, L. A. Fahsingbauer, BS, C. P. Dominguez, C. L. Baum, MD, MS, University of Illinois at Chicago, Chicago, IL. Water-soluble vitamin E(D--tocopheryl polyethylene glycol 1000 succinate (TPGS) may increase oral drug absorption. In vitro and animal data suggest that TPGS inhibits P-gp. It is unknown whether -tocopherol acetate(TA), the more common formulation of vitamin E, has similar drug interaction potential. This study aimed to determine whether TPGS and cause comparable P-gp inhibition in humans. Ten healthy subjects received digoxin 0.5mg POx1 to determine baseline digoxin pharmacokinetics (PK). They then re- ceived TA and TPGS (400 IU PO Q12H x15d) in random order with a 4-week washout between treatments. Digoxin 0.5mg PO was given on days 1 and 15. Serum digoxin concentrations were measured at t0, 0.5, 1, 1.5, 2, 4, 6, 8, 12, and 24 hours; 12-lead EKG was monitored at t0, 3 and 6 hours after each digoxin dose. Genotyping for MDR1(exon 26, C3435T) was determined for variant alleles. Digoxin PK were not different between 3435CC homozygous and 3435C3T allele carriers. Digoxin PK from each treatment were: C max [ng/mL] AUC 0-24 [ngh/mL] 13.73.0 *p0.05 compared with baseline; no EKG changes were observed. (Data are meanSD). In summary, TPGS but not TA, altered PK without affecting pharmacodynamics of digoxin. Changes in digoxin PK with TPGS were not affected by 3435C3T mutation in MDR1 gene. CLINICAL PHARMACOLOGY & THERAPEUTICS 2004;75(2) American Society for Clinical Pharmacology and Therapeutics P95
Transcript of Association of β2-adrenergic receptor (β2AR) haplotype and hypertension in African Americans and...
PDII-A-8HUMAN PHENYLETHANOLAMINE N-METHYLTRANS-
FERASE (PNMT) PHARMACOGENETICS: GENE RESEQUENC-ING AND FUNCTIONAL GENOMIC STUDIES. Y. Ji, O. E.Salavaggione, MD, A. A. Adjei, PhD, B. A. Thomae, B. Eckloff, E.D. Wieben, PhD, R. M. Weinshilboum, MD, Mayo Clinic, Roches-ter, MN.
PNMT (EC 2.1.1.28) catalyzes the N-methylation of norepineph-rine to form epinephrine. We set out to resequence the human PNMTgene, including all exons and introns as well as approximately 1 kbof the 5�-flanking region using Coriell Institute DNA samples from60 African-American (AA) and 60 Caucasian-American (CA) sub-jects. Within the 3.5 kb resequenced, 17 single nucleotide polymor-phisms (SNPs) were observed, including 3 nonsynonymous cSNPs(Asn9Ser, Thr98Ala and Arg112Cys). When constructs for the non-synonymous cSNPs were transiently expressed in COS-1 cells, theAla98 allozyme displayed virtually no enzyme activity or immuno-reactive protein when compared with the wild type (WT) allozyme(P�0.01), while values for the other variant allozymes did not differsignificantly from those for WT. Rabbit reticulocyte lysate studiesshowed that the decrease in immunoreactive protein for the Ala98allozyme was due–at least in part–to accelerated protein degradation.These observations raise the possibility of inherited variation in theability to form epinephrine from norepinephrine.
PDII-A-9ASSOCIATION OF �2-ADRENERGIC RECEPTOR (�2AR)
HAPLOTYPE AND HYPERTENSION IN AFRICAN AMERI-CANS AND CAUCASIANS. B. S. Belgado, PharmD, L. H. Cav-allari, PharmD, T. Langaee, PhD, T. Okorochukwu, A. Sloan, MSC.,J. Johnson, PharmD, University of Florida College of Pharmacy,University of Illinois at Chicago, College of Pharmacy, Gainesville,FL.
The �2AR gene has been associated with hypertension, but dataare conflicting. Racial differences in this association or role of the�2AR haplotype have not been well studied. We sought to determinewhether race and/or haplotype influence the association between the�2AR gene and hypertension. Genetic samples were obtained fromAfrican American (AA) or Caucasian (C) hypertensive (HT) ornormotensive (NT) patients. �2AR codon 16 and 27 genotypes weredetermined by PCR and luciferase-based pyrosequencing. Differ-ences were analyzed by Chi-square and Fisher’s exact test with AAand C analyzed separately. Haplotype frequencies were compared byrace between NT and HT. A total of 482 patients were enrolled.Allele and genotype frequencies were similar for HT and NT atcodons 16 and 27 for both AA and C. No differences were found in�2AR haplotypes between NT and HT for AA or C (Table). Therewere no differences in blood pressure across haplotype for NT AA orC. Our data do not support a significant contribution of the �2ARgene to hypertension risk.
Table. Haplotype frequencies
NT AA (%) HT AA (%) NT C(%) HT C(%)Arg16/Gln27 43 (48.9) 138 (48.9) 96 (38.1) 109 (38.4)
Gly16/Gln27 33 (37.5) 90 (31.9) 59 (23.4) 57 (20.1)
Gly16/Glu27 12 (13.6) 51 (18.1) 95 (37.7) 118 (41.5)
Arg16/Glu27 0 (0) 3 (1.1) 2 (0.8) 0 (0)
PDII-A-10ALPHA-2B ADRENERGIC RECEPTOR (ADRA2B) 301-303
DELETION POLYMORPHISM AND VASCULAR DESENSITI-ZATION IN VIVO. M. Muszkat, MD, G. Sofowora, MD, H. Xie,MD, PhD, P. A. Harris, PhD, A. J. Wood, MD, C. Stein, MD,Vanderbilt University, Nashville, TN.
Alpha-2 adrenergic receptors (ADRA2) play important roles inboth central and peripheral regulation of vascular tone. The ADRA2Bsubtype mediates vasoconstriction and a common genetic variation,301-303 deletion, was associated with loss of agonist-induced desen-sitization in vitro. Desensitization of vascular ADRA2 responses invivo has not been previously described; nor is the effect of geneticvariation known. We examined the hypothesis that 301-303del poly-morphism affects vascular desensitization to the selective ADRA2agonist, dexmedetomidine (Dex) in vivo. Incremental doses of Dex(0.01–1000 ng/min) were infused into a dorsal hand vein (DHV) in28 healthy subjects (age 18-45 years) and responses measured usinga linear variable differential transformer. A dose-response curve wasconstructed and the ED50 calculated. On a separate day, the Dex dosethat had caused at least 50% venoconstriction in the dose-responsestudy was infused for three hours and response measured every 30minutes. The area under the curve for DHV response normalized tothe initial response (nAUC) was calculated. Genotyping for 301-303del was performed, and relation to nAUC was determined. Therewas more than 3-fold inter-individual variability in nAUC. This wasnot related to ADRA2B genotype (p�0.846). Inter-individual vari-ability in vascular responses to ADRA2 agonist over time occurs, butis not explained by the ADRA2B 301-303del.
PDII-B-1VITAMIN E FORMULATION AFFECTS DIGOXIN ABSORP-
TION BY INHIBITING P-GLYCOPROTEIN (P-GP) IN HUMANS.L. Chan, PharmD, L. M. Humma, PharmD, C. A. Schriever, PharmD,MS, L. A. Fahsingbauer, BS, C. P. Dominguez, C. L. Baum, MD,MS, University of Illinois at Chicago, Chicago, IL.
Water-soluble vitamin E(D-�-tocopheryl polyethylene glycol1000 succinate (TPGS) may increase oral drug absorption. In vitroand animal data suggest that TPGS inhibits P-gp. It is unknownwhether �-tocopherol acetate(TA), the more common formulation ofvitamin E, has similar drug interaction potential. This study aimed todetermine whether TPGS and �� cause comparable P-gp inhibitionin humans. Ten healthy subjects received digoxin 0.5mg POx1 todetermine baseline digoxin pharmacokinetics (PK). They then re-ceived TA and TPGS (400 IU PO Q12H x15d) in random order witha 4-week washout between treatments. Digoxin 0.5mg PO was givenon days 1 and 15. Serum digoxin concentrations were measured att�0, 0.5, 1, 1.5, 2, 4, 6, 8, 12, and 24 hours; 12-lead EKG wasmonitored at t�0, 3 and 6 hours after each digoxin dose. Genotypingfor MDR1(exon 26, C3435T) was determined for variant alleles.Digoxin PK were not different between 3435CC homozygous and3435C3T allele carriers. Digoxin PK from each treatment were:
Cmax [ng/mL]AUC0-24 [ng�h/mL] 13.7�3.0
*p�0.05 compared with baseline; no EKG changes were observed. (Data aremean�SD).
In summary, TPGS but not TA, altered PK without affectingpharmacodynamics of digoxin. Changes in digoxin PK with TPGSwere not affected by 3435C3T mutation in MDR1 gene.
CLINICAL PHARMACOLOGY & THERAPEUTICS2004;75(2) American Society for Clinical Pharmacology and Therapeutics P95
