Statistical differences between multiple groups (neopterin and biopterin concentrations in controls and patients with different disorders; GTPCH activity in controls and patients with DRD and GTPCH deficiency) were tested using a one-way ANOVA with pairwise comparison according to Tukey.
REFERENCE VALUES FOR NEOPTERIN AND BIOPTERIN PRODUCTION AND GTPCH ACTIVITY IN STIMULATED CELLS
GTPCH activity was very low in amniocytes but increased in fibroblasts collected after birth (P <0.
In both diseases, GTPCH activity was lower than in controls (P <0.
Furthermore, both neopterin and biopterin are very low in GTPCH deficiency, neopterin is high and biopterin low in PTPS deficiency, and biopterin concentrations are very high in DHPR deficiency (8, 41).
Measurement of GTPCH activity is rather difficult because this enzyme is not expressed in blood cells and fibroblasts.
44) reported that in 40% of DRD patients no mutation was found in the GCH1 gene but that some of them showed reduced GTPCH activity in phytohemagglutinin-stimulated mononuclear blood cells.
GTPCH activity was slightly but not significantly higher when cells were collected during the first year of life.
28) suggested that the possible pattern of pterin production in these cells could be characterized by increased neopterin because of the lack of feedback inhibition of GTPCH by B[H.
GTPCH activity was lower in stimulated fibroblasts from patients with the autosomal dominant form than in those from patients with the autosomal recessive form.
4], tetrahydrobiopterin; GTPCH, GTP cyclohydrolase 1; IFN-[gamma], interferon-[gamma]; TNF-[alpha], tumor necrosis factor-[alpha]; PTPS, 6-pyruvoyltetrahydropterin synthase; SR, sepiapterin reductase; DHPR, dihydropteridine reductase; DRD, Dopa-responsive dystonia; and CSF, cerebrospinal fluid.