Urinary isatin concentrations in patients with Parkinson's disease determined by a newly developed HPLC-LTV method

Isatin, an endogenous monoamine oxidase (MAO) inhibitor, has been found in mammalian tissues. We previously reported that exogenously administered isa tin significantly increased acetylcholine (ACh) and dopamine (DA) levels in the rat striatum. In order to elucidate the relationship between isatin an d Parkinson's disease, we measured urinary isatin excretions in patients wi th Parkinson's disease using a newly developed HPLC-UV method. The recovery of this assay was approximately 102.3% at a range from 2 to 50 nmol/ml. Th e Coefficient of Variance (CV) for the determination at this range was appr oximately 2.5% for intra-assay and 6.2% for inter-assay, respectively. Ther e was no significant difference in urinary isatin excretion between data fr om men and women in healthy control. The value in young age group (19-35 ye ars old) was not significantly different compared with that of the older ag e group (54-84 years old). Urinary isatin levels in patients with Parkinson 's disease tended to increase in accordance to the Hoehn and Yahr criteria. This is the first study in which a significant increase in urinary isatin excretion was observed at Stage III, IV and V in patients with Parkinson's disease. Urinary isatin concentrations in drug-treated patients with Parkin son's disease (at Stage I and II) tended to decrease compared with those of patients without medication. These results demonstrated that urinary isati n excretion may serve as an endogenous diagnostic marker for the clinical s everity of Parkinson's disease.