TABLE 1.

Distribution of ThTP in subcellular fractions from rat brain

Subcellular fractions were isolated on a Percoll gradient, and ThTP was determined in each fraction by HPLC. The specific activities of two marker enzymes (fumarase and LDH) were measured in the synaptosomal and mitochondrial fractions. ThTP synthesis was determined in synaptosomes and free mitochondria. To estimate the rate of synthesis, the ThTP content of mitochondria was measured after a 10-min incubation (37 °C) in the presence of ThDP (1 mm), succinate (5 mm), and P_i (5 mm). The incubation medium contained KCl (140 mm), MgCl₂ (2 mm), EGTA (0.5 mm), K-MOPS (10 mm, pH adjusted to 7.3 with KOH). Means ± S.D. for four experiments.

	ThTP content	Fumarase	LDH	ThTP synthesis
	pmol mg−1	nmol mg−1min−1	nmol mg−1min−1	pmol mg−110 min−1
Homogenate	0.59 ± 0.24
P1	0.99 ± 0.36
Myelin	0.40 ± 0.08
Synaptosomes	0.70 ± 0.21	0.38 ± 0.06	1.4 ± 0.2	4.6 ± 0.7
Mitochondria	3.5 ± 0.6a	1.04 ± 0.07b	0.19 ± 0.01a	60 ± 4c

^ap < 0.01, analysis of variance followed by Dunnett's test for comparison with the synaptosomes.

^b p < 0.05.

^c p < 0.001.