Takatsu H, Scheffel U, Fujiwara H
Second Department of Internal Medicine, Gifu University School of Medicine, Japan.
J Nucl Cardiol. 1995 Nov-Dec;2(6):507-12. doi: 10.1016/s1071-3581(05)80043-1.
Because it is not metabolized as is norepinephrine (NE), most of the metaiodobenzylguanidine (MIBG) taken up by the heart is considered to be lost subsequently by release concomitant with sympathetic stimulation. Therefore we examined whether the washout of MIBG is influenced by sympathetic tone, which we modulated by using immobilization stress or activation of the renin-angiotensin system (RAS).
In 175 male ddY mice, left ventricular radioactivity was counted 30 minutes or 4 hours after injection of 74 kBq (2 microCi) of iodine 125- or iodine 131-labeled MIBG (125I- or 131I-MIBG). The washout rates of MIBG were determined under immobilization stress or under sodium loading or restriction in combination with losartan (10 mg/kg) or cilazapril (1 mg/kg) pretreatment. Immobilization enhanced the washout of 125I-MIBG (80.9% vs 57.9% in the control animals); this was determined to be related to washout from the neuronal compartment, because the nonneuronal component assessed through desipramine pretreatment was not affected. Pretreatment with losartan or cilazapril decreased the facilitation of 125I-MIBG washout in sodium-restricted mice (40.9% and 33.7%, respectively, vs 43.5% in the control animals), but not in sodium-loaded mice.
Measurement of MIBG washout may be feasible for determining the changes in sympathetic tone caused by immobilization stress or activation of the RAS.
由于间碘苄胍（MIBG）不像去甲肾上腺素（NE）那样被代谢，心脏摄取的大部分MIBG随后被认为会随着交感神经刺激而释放并流失。因此，我们研究了MIBG的洗脱是否受交感神经张力的影响，我们通过使用固定应激或激活肾素 - 血管紧张素系统（RAS）来调节交感神经张力。
在175只雄性ddY小鼠中，注射74 kBq（2微居里）的碘125或碘131标记的MIBG（125I - MIBG或131I - MIBG）后30分钟或4小时对左心室放射性进行计数。在固定应激或钠负荷或限制的情况下，联合氯沙坦（10 mg/kg）或西拉普利（1 mg/kg）预处理来测定MIBG的洗脱率。固定增强了125I - MIBG的洗脱（80.9% vs 对照动物中的57.9%）；这被确定与从神经区室的洗脱有关，因为通过地昔帕明预处理评估的非神经成分未受影响。氯沙坦或西拉普利预处理降低了钠限制小鼠中125I - MIBG洗脱的促进作用（分别为40.9%和33.7%，vs 对照动物中的43.5%），但在钠负荷小鼠中未降低。
测量MIBG洗脱对于确定由固定应激或RAS激活引起的交感神经张力变化可能是可行的。
