Isovolumic loading of the failing heart by intraventricular placement of a spring expander attenuates cardiac atrophy after heterotopic heart transplantation.

Cardiac atrophy is the most common complication of prolonged application of the left ventricle (LV) assist device (LVAD) in patients with advanced heart failure (HF). Our aim was to evaluate the course of unloading-induced cardiac atrophy in rats with failing hearts, and to examine if increased isovolumic loading obtained by intraventricular implantation of an especially designed spring expander would attenuate this process. Heterotopic abdominal heart transplantation (HTx) was used as a rat model of heart unloading. HF was induced by volume overload achieved by creation of the aorto-caval fistula (ACF). The degree of cardiac atrophy was assessed as the weight ratio of the heterotopically transplanted heart (HW) to the control heart. Isovolumic loading was increased by intraventricular implantation of a stainless steel three-branch spring expander. The course of cardiac atrophy was evaluated on days 7, 14, 21, and 28 after HTx Seven days unloading by HTx in failing hearts sufficed to substantially decrease the HW (-59 ± 3%), the decrease progressed when measured on days 14, 21, and 28 after HTx Implantation of the spring expander significantly reduced the decreases in whole HW at all the time points (-39 ± 3 compared with -59 ± 3, -52 ± 2 compared with -69 ± 3, -51 ± 2 compared with -71 ± 2, and -44 ± 2 compared with -71 ± 3%, respectively; P<0.05 in each case). We conclude that the enhanced isovolumic heart loading obtained by implantation of the spring expander attenuates the development of unloading-induced cardiac atrophy in the failing rat heart.

Radioprotective effects of amifostine (WR-2721) or cystamine on radiation damage and its repair in rats whole body exposed to fission neutrons.

Sulphur containing radioprotective drugs amifostine (gammaphos, WR-2721) or cystamine (disulfide of meracaptoethylamine) of Czechoslovak production were examined in whole body fission neutrons irradiated rats in the thermal column of reactor VVR-S. Using the split-dose technic the first sublethal neutron dose in the range 1-2 Gy was followed by second lethal exposures in the two time intervals (3 or 6 days) using whole body fission neutrons irradiations (3 days interval) or whole body gamma-irradiations (6 days interval) for LD50/30 evaluation within next 30 days survival observation. In other experiments the mean survival time (MST) in days was estimated in different rats group, when animals were whole body fission neutrons irradiated twice with 3-days interval using the total lethal doses of 4 or 5 Gy. Protected rats received amifostine (160 mg.kg(-1) i.p. and 200 mg.kg(-1) i.m.) or cystamine (40 mg.kg(-1) i.p. and 50 mg.kg(-1) i.m.), control rats obtained saline 20 min before beginning of irradiation in the amount of 0.5 ml.100 g(-1) of the rat's body weight. Non-significant DRF value 1.13 for WR-2721 i.p. was calculated in survival studies in rats twice neutron irradiated with 3 days interval (DRF 1.04 for cystamine). Chemical protectors were administered before each neutron exposure. MST of twice neutron lethal iradiated rats was prolonged not regularly by radioprotectors tested. WR-2721 and cystamine i.m. were not able to increase 6 days reparation processes after sublethal 2 Gy fission neutrons whole body irradiated rats.