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S230 Abstracts Heart, Lung and Circulation2008;17S:S219–S241

521Isopropylamine NONOate (IPA/NO) Prevents Cardiomy-ocyte Hypertrophy via Nitroxyl (HNO)/cGMP-DependentSignalling

Rebecca Ritchie 1,∗, Swati Gossain 1, Jennifer Irvine 1,David Kaye 1, Barbara Kemp-Harper 2

1 Heart Failure Research Group, Baker Heart Research Institute,Melbourne, Victoria, Australia; 2 Department of Pharmacology,Monash University, Melbourne, Victoria, Australia

We have previously shown that NO•/cGMP signalling isan important anti-hypertrophic mechanism in the heart.HNO is the one electron reduction of NO•, thought toelicit cardiovascular actions via cGMP and/or calcitoningene-related peptide (CGRP). We tested the hypothe-sis that IPA/NO prevents cardiomyocyte hypertrophy viaHNO/cGMP and CGRP-dependent signalling, in neona-tal rat cardiomyocytes, and compared its efficacy withthe NO• donor, DEA/NO. IPA/NO (0.1–3 �M, replenished3× per day) elicited concentration-dependent inhibi-tion of endothelin-1 (ET-1, 60 nM)-induced cardiomyocytehypertrophy, After 48 h, the highest concentration ofIPA/NO decreased two dimensional area from 255 ± 28%to 96 ± 27% of paired control (n = 4, p < 0.001). The antihy-pertrophic action of IPA/NO was significantly attenuatedin the presence of the HNO scavenger, L-cysteine (3 mM)or the cGMP-dependent protein kinase inhibitor, Rp-

522Differential Activities of Cardiac Hypertrophic SignallingPathways in Neonatal and Adult Hypertrophic Heart Rats(HHR)

James Bell 1,∗, Enzo Porrello 1, Stephen Harrap 1, WalterThomas 2, Lea Delbridge 1

1 University of Melbourne, Melbourne, Victoria, Australia;2 University of Queensland, Brisbane, Queensland, Australia

There is increasing evidence that early growth ‘pro-gramming’ may be important in predisposing for adultcardiovascular disease states. The extent to which peri-natal modulation of heart growth determines laterdevelopment of cardiac hypertrophy has not been estab-lished. We have previously reported that the HypertrophicHeart Rat (HHR), a normotensive model of adult primarycardiac hypertrophy, exhibits neonatal cardiac growthrestriction relative to the control Normal Heart Rat (NHR).In this study our goal was to compare the expression andactivation of selected intermediates of growth signallingpathways in the adult and young HHR and NHR.Cardiac tissues were recovered from male adult (12 weeks,n = 10) and from neonatal (p2, n = 7) NHR/HHR underanaesthesia. Myocardial homogenates were centrifuged(3000 × g, 5 min, 4 ◦C) to recover cytosolic fractions forWestern blot analysis (quantified as relative expressionunits). Despite the existence of marked hypertrophy in

8 PCTP cGMPS (10 �M, both n = 4, p < 0.05), but wasunaffected by the NO• scavenger carboxy-PTIO (200 �M)or the CGRP antagonist, CGRP(8-37) (1 �M, both n = 4).DEA/NO elicited similar concentration-dependent inhi-bition of ET-1-induced cardiomyocyte hypertrophy. BothIPA/NO and DEA/NO also blocked ET-1-induced car-diomyocyte superoxide generation (both n = 4, p < 0.001),a key trigger of cardiomyocyte hypertrophy. None of theseagents alone, or their respective vehicles, affected cell sizeof superoxide. Finally, using an NO•-sensing electrode,we demonstrated that DEA/NO, but not IPA/NO, releasesNO• under our cell culture conditions. In conclusion, ourresults provide evidence that IPA/NO prevents cardiomy-ocyte hypertrophy via HNO activation of cGMP signalling.Although the antihypertrophic and antioxidant efficacyof IPA/NO was comparable to NO•, there is no role forextracellular oxidation of HNO to NO• or CGRP-mediatedsignalling in these IPA/NO actions. These studies may ulti-mately facilitate the development of HNO donors such asIPA/NO as novel antihypertrophic therapy for patients atrisk of developing heart failure.

doi:10.1016/j.hlc.2008.05.575

the adult HHR hearts, no changes were observed (vs.NHR) in the phosphorylation states of Akt (1.14 ± 0.09 vs.1.00 ± 0.05, HHR vs. NHR, p = ns), GSK3� (1.14 ± 0.12 vs.1.00 ± 0.12, p = ns) and ERK1/2 (1.03 ± 0.04 vs. 1.00 ± 0.04,p = ns), or in total calcineurin expression (1.19 ± 0.10vs. 1.00 ± 0.10, p = ns). Neonatal (growth restricted)HHR hearts exhibited increased Akt phosphorylation(2.31 ± 0.53 vs. 0.99 ± 0.07, p = 0.029), with decreased phos-phorylation of both GSK3� (0.46 ± 0.06 vs. 1.00 ± 0.17,p < 0.01) and ERK1/2 (0.82 ± 0.04 vs. 1.00 ± 0.05, p < 0.01).Calcineurin expression was unchanged (0.98 ± 0.09 vs.1.00 ± 0.05, p = ns). In the neonates these shifts areconsistent with augmented PI3K pathway-dependent‘physiological’ growth signalling.This study suggests hearts with a genetic pre-dispositionfor hypertrophy are ‘programmed’ early in developmentfor later hypertrophic growth through transient, but notsustained, modulation of specific growth signalling path-ways.

doi:10.1016/j.hlc.2008.05.576