Clinical significance of striatal DOPA decarboxylase activity in Parkinson's disease.

Abstract

UNLABELLED:

We performed dynamic PET studies with fluorodopa (FDOPA) in 9 normal volunteers and 16 patients with Parkinson's disease to investigate the applicability of dopa decarboxylase (DDC) activity measurements as useful markers of the parkinsonian disease process.

METHODS:

From the 3-O-methyl-FDOPA (3OMFD)/PET studies, we obtained mean population values of the kinetic rate constants for 3OMFD (K1M = 0.0400 and k2M = 0.0420). We applied these values to calculate striatal DDC activity using the FDOPA compartmental model. We estimated k3D in this group using dynamic FDOPA-PET and population mean K1M and k2M values. We then applied the mean population K1M and k2M values to estimate k3D(pop) to a new group (6 normal volunteers and 11 patients) studied only with dynamic FDOPA-PET. In all FDOPA/PET studies, we calculated striatal uptake rate constants (KiFD) using a graphical method and also measured the striato-occipital ratio (SOR).

RESULTS:

Although DDC activity has been postulated as a precise indicator of presynaptic nigrostriatal dopaminergic function, KiFD and SOR provided better between-group discrimination than did estimates of striatal DDC activity. KiFD and k3D(pop) both correlated significantly with quantitative disease severity ratings, with a similar degree of accuracy (r = 0.69 and 0.63 for k3D(pop) and KiFD, respectively; p < 0.01).

CONCLUSION:

Although estimated striatal DDC activity correlates with clinical disability, this measure is comparably less effective for early diagnosis. We conclude that a simple estimate such as striatal KiFD is superior to k3D measurements for most clinical and research applications.

• Authors: T Ishikawa, V Dhawan, T Chaly, C Margouleff, W Robeson, J R Dahl, F Mandel, P Spetsieris, D Eidelberg
• Journal: Journal of nuclear medicine : official publication, Society of Nuclear Medicine (J Nucl Med) Vol. 37 Issue 2 Pg. 216-22 (Feb 1996) ISSN: 0161-5505 [Print] United States
• PMID: 8667047 (Publication Type: Comparative Study, Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Fluorine Radioisotopes
• 3-O-methyl-6-fluoro-dopa
• fluorodopa F 18
• Dihydroxyphenylalanine
• Dopa Decarboxylase

Topics

• Brain (diagnostic imaging, enzymology)
• Case-Control Studies
• Corpus Striatum (enzymology)
• Dihydroxyphenylalanine (analogs & derivatives, pharmacokinetics)
• Dopa Decarboxylase (metabolism)
• Female
• Fluorine Radioisotopes
• Humans
• Image Processing, Computer-Assisted
• Male
• Middle Aged
• Models, Biological
• Parkinson Disease (diagnostic imaging, enzymology)
• Tomography, Emission-Computed (methods)