title: Exercise training improves myocardial tolerance to ischemia in male but not in female rats.
abstract: Acute exercise increases myocardial tolerance to ischemia-reperfusion (I-R) injury in male but not in female rat hearts, possibly due to a decreased heat shock protein 70 (Hsp70) response in the female hearts. This study examined whether repetitive exercise training would increase Hsp70 and myocardial tolerance to I-R injury in female rat hearts. Adaptations in myocardial manganese superoxide dismutase (MnSOD) and endothelial nitric oxide synthase (eNOS) were also assessed. Ten-week old male (M) and female (F) Sprague-Dawley rats (n = 40 total) exercise-trained for 14 wk; the last 8 wk consisted of running 1 h at 30 m/min (2% incline), 5 days/wk. Following training, left ventricle mechanical function (LVMF) was monitored for 30 min of reperfusion following 30 min of global ischemia (Langendorff procedure). Myocardial Hsp70 content was not different in M and F control groups, while increases were observed in both trained groups (M greater than F; P < 0.05). Although MnSOD content did not differ between groups, endothelial nitric oxide synthase (eNOS) levels were decreased in F, with no change in M, following training (P < 0.05). Hearts from control F demonstrated a greater recuperation of all indices of LVMF following I-R compared with control M hearts (P < 0.05). Hearts of trained M exhibited improved recovery of LVMF (left ventricular diastolic pressure, left ventricular end-diastolic pressure, +dP/dt, -dP/dt) during reperfusion compared with control M hearts (P < 0.05). In contrast, hearts of trained F did not show any change in recovery from I-R. Hence, exercise training is more beneficial to M than F in improving myocardial function following I-R injury.
authors.affiliation: Exercise Biochemistry Laboratory, School of Kinesiology, The University of Western Ontario, London, Ontario, Canada.
authors.forename: David B
authors.initials: DB
authors.lastname: Thorp
authors.forename: James V
authors.initials: JV
authors.lastname: Haist
authors.forename: Jennifer
authors.initials: J
authors.lastname: Leppard
authors.forename: Kevin J
authors.initials: KJ
authors.lastname: Milne
authors.forename: Morris
authors.initials: M
authors.lastname: Karmazyn
authors.forename: Earl G
authors.initials: EG
authors.lastname: Noble
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002950:Citrate (si)-Synthase / Q000378:metabolism; D005260:Female; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism; D066298:In Vitro Techniques; D008297:Male; D009200:Myocardial Contraction / Q000502:physiology; D017202:Myocardial Ischemia / Q000503:physiopathology*; D009206:Myocardium / Q000201:enzymology; D032383:Myocytes, Cardiac / Q000201:enzymology / Q000502:physiology; D052250:Nitric Oxide Synthase Type III / Q000378:metabolism; D010805:Physical Conditioning, Animal / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012727:Sex Characteristics; D013482:Superoxide Dismutase / Q000378:metabolism; D016277:Ventricular Function, Left / Q000502:physiology
chemical_list: D018840:HSP70 Heat-Shock Proteins; D052250:Nitric Oxide Synthase Type III; D013482:Superoxide Dismutase; D002950:Citrate (si)-Synthase