Kontracepcija

<div><p>Aims</p><p>To determine the mechanisms by which the α_1A-adrenergic receptor (AR) regulates cardiac contractility.</p><p>Background</p><p>We reported previously that transgenic mice with cardiac-restricted α_1A-AR overexpression (α_1A-TG) exhibit enhanced contractility but not hypertrophy, despite evidence implicating this Gα_q/11-coupled receptor in hypertrophy.</p><p>Methods</p><p>Contractility, calcium (Ca²⁺) kinetics and sensitivity, and contractile proteins were examined in cardiomyocytes, isolated hearts and skinned fibers from α_1A-TG mice (170-fold overexpression) and their non-TG littermates (NTL) before and after α_1A-AR agonist stimulation and blockade, angiotensin II (AngII), and Rho kinase (ROCK) inhibition.</p><p>Results</p><p>Hypercontractility without hypertrophy with α_1A-AR overexpression is shown to result from increased intracellular Ca²⁺ release in response to agonist, augmenting the systolic amplitude of the intracellular Ca²⁺ concentration [Ca²⁺]_i transient without changing resting [Ca²⁺]_i. In the <i>absence</i> of agonist, however, α_1A-AR overexpression <i>reduced</i> contractility despite unchanged [Ca²⁺]_i. This hypocontractility is not due to heterologous desensitization: the contractile response to AngII, acting via its Gα_q/11-coupled receptor, was unaltered. Rather, the hypocontractility is a pleiotropic signaling effect of the α_1A-AR in the absence of agonist, inhibiting RhoA/ROCK activity, resulting in hypophosphorylation of both myosin phosphatase targeting subunit 1 (MYPT1) and cardiac myosin light chain 2 (cMLC2), reducing the Ca²⁺ sensitivity of the contractile machinery: all these effects were rapidly reversed by selective α_1A-AR blockade. Critically, ROCK inhibition in normal hearts of NTLs without α_1A-AR overexpression caused hypophosphorylation of both MYPT1 and cMLC2, and rapidly reduced basal contractility.</p><p>Conclusions</p><p>We report for the first time pleiotropic α_1A-AR signaling and the physiological role of RhoA/ROCK signaling in maintaining contractility in the normal heart.</p></div

GATA4 genotypes of German cohort.

<p>GATA4 genotypes of German cohort.</p

Clinical characteristics¹ of German cohort.

1<p>Family history was unknown for 54 cases with ASDII and 37 cases with PFO. Other Clinical characteristics were unknown for a small number of patients.</p>2<p>All ASDII cases were free of any other cardiac malformation.</p>3<p>All PFO cases were free of any other cardiac malformation. All were designated as having cryptogenic stroke.</p>4<p>Neurologic event includes thromboembolic stroke, PRIND (prolonged reversible ischemic neurologic deficit) and TIA.</p>5<p>Defect closure includes interventional closure and surgical closure.</p>6<p>AVB: electrocardiographic atrioventricular block.</p>7<p>iRSB/RSB: (incomplete) right bundle block.</p

S377G allele distribution in indigenous human populations.

1<p>Reflects the prevalence of the A>G single nucleotide polymorphism that causes the S377G amino acid change.</p>2<p>The same population were used as “population controls” in the Australian cohort.</p

Pooled genotype data from Australian and German Cohorts.

<p>Pooled genotype data from Australian and German Cohorts.</p

GATA4 genotypes of Australian cohort.

1<p>p = 0.02 compared to TEE Controls; Odds ratio 2.16.</p

Contractility in α_1A-TG isolated working hearts.

<p><b>A,</b> baseline left ventricular systolic pressure (LVSP), dP/dt_max and dP/dt_min of isolated perfused contracting NTL (n = 17) and α_1A-TG (n = 24) hearts. <b>B,</b> representative recordings of left ventricular pressure (LVP) and dP/dt at baseline and during A61603 infusion (100 pM). <b>C,</b> composite data obtained from NTL (◊, n = 6) and α_1A-TG (•, n = 7) hearts at baseline (C) and dose-response to A61603. Data are shown as the mean ± SEM. *<i>P</i><0.05, *<i>*P<</i>0.01; ***P<0.001 vs. NTL.</p

Hypocontractility in α_1A-TG hearts is not due to heterologous desensitization but is mediated by the α_1A-AR.

<p><b>A,</b> representative recordings of left ventricular pressure (LVP) and dP/dt at baseline and during AngII infusion (100 nM) in isolated perfused contracting hearts. <b>B,</b> composite data at baseline (Control) and after AngII infusion (100 nM) for 10 min in NTL (□, n = 7) and α_1A-TG (▪, n = 9) hearts; <b>C,</b> change (Δ) from baseline for B; <b>D,</b> representative recordings of LVP and dP/dt at baseline and during α_1A-AR selective antagonist, RS100329, infusion (50 nM); <b>E,</b> composite data at baseline (Control) and after RS100329 infusion (50 nM) for 10 min in NTL (□, n = 5) and α_1A-TG (▪, n = 4) hearts. Data are shown as the mean ± SEM. *<i>P</i><0.05, **<i>P</i><0.01, ***<i>P</i><0.001.</p

Contractility in α_1A-TG cardiomyocytes.

<p>Indices of excitation-contraction coupling before and after α_1A-AR agonist stimulation with phenylephrine (PE) in NTL (◊, n = 7) and α_1A-TG (•, n = 7) CMs. <b>A,</b> basal [Ca²⁺]_I; <b>B,</b> amplitude of the systolic [Ca²⁺]_i rise (Peak-Basal); <b>C,</b> percent cell shortening. Data are shown as the mean ± SEM. <i>*P<</i>0.05 vs. NTL.</p

Mechanism of α_1A-TG hypocontractility.

<p>Western blot analyses of myofilament proteins and RhoA activity in NTL (□) and α_1A-TG (▪) hearts after infusion of saline or RS100329 (50 nM) for 8 min. In each panel, representative Western blots and pooled data (n = 3/group) are shown: <b>A,</b> p-cMLC2(Ser20), total cMLC2, and their ratio; <b>B,</b> p-MYPT1(Thr696), total MYPT1, and their ratio; <b>C,</b> RhoA protein expression, RhoA activity and the relationship between dP/dt_max and RhoA activity, where data are shown from NTL isolated hearts treated with saline (○) or RS100329 (•) and α_1A-TG hearts treated with saline (Δ) or RS100329 (▴). Western blot data are normalized to GAPDH expression. Data are shown as the mean ± SEM. <i>*P<</i>0.05, *<i>*P<</i>0.01.</p