Diagnostic performance of 64-slice multidetector coronary computed tomographic angiography in women.

BACKGROUND: Diagnostic approach to chest pain in women is challenging, but still under-investigated. The purpose of this study was to assess the diagnostic performance of 64-slice multidetector coronary computed tomographic angiography (CCTA) in women with chest pain. METHODS AND RESULTS: We included 606 patients--255 women and 351 men (mean age 61 ± 12 years for both)--who had been referred for a CCTA and an invasive coronary angiography (diagnostic standard) because of chest pain, either as part of clinical work-up in two urban medical centers or as part of the multicenter ACCURACY trial. On a patient-based model, the sensitivity, specificity, and positive predictive value (PPV) and negative predictive value to detect ≥50% and ≥70% stenosis were 98%, 84%, 87%, and 97% and 96%, 83%, 77%, and 97%, respectively, for women and 97%, 83%, 89%, and 95% and 94%, 91%, 90%, and 94%, respectively, for men. There were no statistically significant differences between men and women in diagnostic performance measures except for the PPV of detecting a ≥70% stenosis (P = .007). CONCLUSION: In women with chest pain, 64-slice multidetector CCTA is at least as sensitive and specific as in men. Our findings suggest that CCTA is a promising diagnostic tool for timely detection and/or exclusion of CAD in symptomatic intermediate-risk female populations.

Sex comparison of diagnostic accuracy of 64-multidetector row coronary computed tomographic angiography: results from the multicenter ACCURACY trial.

BACKGROUND: The diagnosis of coronary artery disease (CAD) in women remains a challenge, given their lower prevalence of obstructive disease and the suboptimal performance of traditional noninvasive tests (exercise electrocardiography and stress myocardial perfusion imaging). Coronary computed tomographic angiography (CTA) is a validated method for detection and exclusion of obstructive coronary artery stenosis. OBJECTIVES: We compared the diagnostic accuracy of coronary CTA between men and women without known CAD with the use of invasive coronary angiography (ICA) as the reference standard. METHODS: We prospectively evaluated 230 subjects with chest pain at 16 sites who were clinically referred for ICA. ICAs were evaluated for coronary stenosis according to quantitative coronary angiography. RESULTS: Subjects (136 men and 94 women; mean ± age, 57 ± 10 years) underwent both CTA and ICA. For a patient-based model for stenosis >50%, sensitivity, specificity, positive and negative predictive values in men versus women were 96%, 78%, 69%, 100% and 90%, 88%, 47%, 99%, respectively. Subgroup analyses were performed for age and lifestyle risk factors. For stenosis > 50% in patients < 55 years, specificity in men versus women was 88% versus 95%, whereas for patients > 55 years, specificity in men versus women was 68% versus 82% (P < 0.05). CONCLUSIONS: Coronary CTA found comparable diagnostic accuracy for women in comparison with men for the detection of obstructive coronary stenosis at both thresholds of 50% and 70%.

Novel parathyroid hormone (PTH) antagonists that bind to the juxtamembrane portion of the PTH/PTH-related protein receptor.

Current antagonists for the parathyroid hormone (PTH)/PTH-related protein (PTHrP) receptor (PTHR) are N-terminally truncated or N-terminally modified analogs of PTH(1-34) or PTHrP(1-34) and are thought to bind predominantly to the N-terminal extracellular (N) domain of the receptor. We hypothesized that ligands that bind only to PTHR region comprised of the extracellular loops and seven transmembrane helices (the juxtamembrane or J domain) could also antagonize the PTHR. To test this, we started with the J domain-selective agonists [Gln(10),Ala(12),Har(11),Trp(14),Arg(19) (M)]PTH(1-21), [M]PTH(1-15), and [M]PTH(1-14), and introduced substitutions at positions 1-3 that were predicted to dissociate PTHR binding and cAMP signaling activities. Strong dissociation was observed with the tri-residue sequence diethylglycine (Deg)(1)-para-benzoyl-l-phenylalanine (Bpa)(2)-Deg(3). In HKRK-B7 cells, which express the cloned human PTHR, [Deg(1,3),Bpa(2),M]PTH(1-21), [Deg(1,3),Bpa(2),M]PTH(1-15), and [Deg(1,3),Bpa(2),M]PTH(1-14) fully inhibited (IC(50)s = 100-700 nm) the binding of (125)I-[alpha-aminoisobutyric acid(1,3),M]PTH(1-15) and were severely defective for stimulating cAMP accumulation. In ROS 17/2.8 cells, which express the native rat PTHR, [Deg(1,3),Bpa(2),M]PTH(1-21) and [Deg(1,3),Bpa(2),M]PTH(1-15) antagonized the cAMP-agonist action of PTH(1-34), as did PTHrP(5-36) (IC(50)s = 0.7 microm, 2.6 microm, and 36 nm, respectively). In COS-7 cells expressing PTHR-delNt, which lacks the N domain of the receptor, [Deg(1,3),Bpa(2), M]PTH(1-21) and [Deg(1,3),Bpa(2),M]PTH(1-15) inhibited the agonist actions of [alpha-aminoisobutyric acid(1,3)]PTH(1-34) and [M]PTH(1-14) (IC(50)s approximately 1 microm), whereas PTHrP(5-36) failed to inhibit. [Deg(1,3),Bpa(2),M]PTH(1-14) inhibited the constitutive cAMP-signaling activity of PTHR-tether-PTH(1-9), in which the PTH(1-9) sequence is covalently linked to the PTHR J domain, as well as that of PTHR(cam)H223R. Thus, the J-domain-selective N-terminal PTH fragment analogs can function as antagonists as well as inverse agonists for the PTHR. The new ligands described should be useful for further studies of the ligand binding and activation mechanisms that operate in the critical PTHR J domain.

Identification of a contact site for residue 19 of parathyroid hormone (PTH) and PTH-related protein analogs in transmembrane domain two of the type 1 PTH receptor.

Recent functional studies have suggested that position 19 in PTH interacts with the portion of the PTH-1 receptor (P1R) that contains the extracellular loops and seven transmembrance helices (TMs) (the J domain). We tested this hypothesis using the photoaffinity cross-linking approach. A PTHrP(1-36) analog and a conformationally constrained PTH(1-21) analog, each containing para-benzoyl-l-phenylalanine (Bpa) at position 19, each cross-linked efficiently to the P1R expressed in COS-7 cells, and digestive mapping analysis localized the cross-linked site to the interval (Leu232-Lys240) at the extracellular end of TM2. Point mutation analysis identified Ala234, Val235, and Lys240 as determinants of cross-linking efficiency, and the Lys240-->Ala mutation selectively impaired the binding of PTH(1-21) and PTH(1-19) analogs, relative to that of PTH(1-15) analogs. The findings support the hypothesis that residue 19 of the receptor-bound ligand contacts, or is close to, the P1R J domain-specifically, Lys240 at the extracellular end of TM2. The findings also support a molecular model in which the 1-21 region of PTH binds to the extracellular face of the P1R J domain as an alpha-helix.

Residue 19 of the parathyroid hormone (PTH) modulates ligand interaction with the juxtamembrane region of the PTH-1 receptor.

Recent data suggest that the binding of parathyroid hormone (PTH)-(1-34) to the PTH-1 receptor (P1R) involves a high-affinity interaction between the C-terminal (15-34) domain of the ligand and the amino-terminal extracellular (N) domain of the receptor and a low-affinity interaction between the N-terminal (1-14) portion of PTH and the juxtamembrane (J) region of the receptor, with the latter interaction giving rise to signal transduction. We investigated whether residues C-terminal of position 14 in PTH(1-34) contribute to the J component of the interaction mechanism by comparing the capacity of PTH analogues N-terminally modified to improve J domain affinity and C-terminally truncated at position 14, 20, or 34 to stimulate cAMP formation in COS-7 cells transiently transfected with P1R-delNt, a P1R construct that lacks most of the N domain. In these cells, the potency of [M]PTH(1-34) (M = Ala(1,3,12),Gln(10),Har(11),Trp(14),Arg(19)) was 120-fold greater than that of [M]PTH(1-14) (EC(50)s = 3.0 +/- 0.8 and 360 +/- 90 nM, respectively) but was equal to that of [M]PTH(1-20) (EC(50) = 2.3 +/- 0.3 nM). Reverting the Arg(19) substitution of [M]PTH(1-20) to the native Glu reduced cAMP signaling potency on P1R-delNt by 12-fold (EC(50) of [M]PTH(1-20)-Glu(19) = 27 +/- 4 nM), and it decreased the analog's capacity to inhibit the binding of the J domain-selective radioligand, (125)I-[Aib(1,3),Nle(8),M,Tyr(21)]ratPTH(1-21), to the full-length P1R stably expressed in LLC-PK1 cells by 40-fold. The Glu(19) --> Arg modification, however, did not affect the capacity of PTH(15-31) to inhibit the binding of the N domain-selective radioligand (125)I-bPTH(3-34) to the full-length receptor. The overall data suggest that residues (15-20) of PTH, and particularly residue 19, contribute to the capacity of the N-terminal portion of the ligand to interact with the juxtamembrane region of the receptor. The NMR data presented in the accompanying manuscript suggests that this role could involve intramolecular effects on secondary structure in the N-terminal portion of the ligand.