|Budget Amount *help
¥1,400,000 (Direct Cost: ¥1,400,000)
Fiscal Year 1995: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 1994: ¥900,000 (Direct Cost: ¥900,000)
We investigated the extent of a down regulation to catecholamine treatment using isolated perfused rat hearts. The animals were assigned randomly to two groups of six animals each. The control group received subcutaneously physiologic saline (4.8 ml/day) for 6 days via the catheter inserted into the nape of the animal. The isoproterenol group received a 10 mg/kg dose of isoproterenol, which was diluted in 4.8 ml of physiologic saline and infused via the catheter by the same means of the control group. The animal was anesthetized with an inhalation of ethyl ether. After thoracotomy, the heart was rapidly excised and immersed in ice-cold buffer. The aorta mounted onto a cannula attached to a perfusion apparatus and retrograde perfusion of the heart was started in the Langendorff's working heart mode at a constant pressure.
Although heart rate and coronary flow remained transiently at low values due to the low temperature and insufficient oxygen supply in the initial period of the perfusion, they recovered well within SAO minutes. Heart rate and coronary flow were determined and recorded at 30 minutes (the control values), 1,2, and 3 hours after the initiation of the perfusion. Heart rate in the control group showed nearly the same values as those of whole animal. Thereafter, while heart rate decreased slightly, it remained stable over a period of 5 hours. This suggested that our method was appropriate to maintain the function of isolated perfused heart In contrast, in the isoproterenol group, heart rate and coronary flow decreased 25% and 30% of the control value, respectively. These results also suggested that continuous subcutaneous administration of isoproterenol certainly produced a down regulation. A further examination is needed to ascertain whether steroid hormone produces up regulation.