According to Matsukawa (1), thiamine propyl disulfide (TPD) owes its good absorp tion and rapid transference to the tissues to its fat-soluble property . However, much remains to be settled as to the role the propylmercapto radical of TPD played in its transference to the tissues. TPD labeled with radioactive isotope may prove a useful tool in the study of the mechanism of absorption of TPD . This paper deals with the results of the experiments carried out on this subject in animals using TPD-S35.
EXPERIMENTAL
Specimens of TPD-S35There are two S atoms in the molecule of TPD . In the present experiments two kinds of TPD-S35 were used. One had S35 in the thiazole part , TPD-S35(inner), and the other in the propylmercapto radical , TPD-S35(outer) (Fig. 1). The specimens of TPD-S35 used in the present experiments were synthesized at the laboratories of Takeda Pharmaceutical Co., Ltd ., Osaka. The specific radioactivity of TPD-S35(outer) was 2.8 or 5.0 and that of TPD-S35(inner) 1.5 or 2 .9 mc/g. radical is dissociated from TPD and a volatile sulfur compound is formed since SSlinkage is relatively unstable. This can be attested by the decrease in S35 counts. Therefore, the estimation of S35 should be in the form of BaSO4-S35. The self-absorption curve of BaSO4-S35 showed that the measurement of its radioactivity could best be conducted with a thickness of 4 to 10mg/cm2 (20 to 50 mg of BaSO4-S35 per one Petri dish of 5.4cm2).The radioactives of BaSO4-S35 in a thickness of this range were estimated, and the counts were corrected for standard thickness (30 mg per one dish) by a correc tion curve. In actual practice, 9 to 15 mg of Na2SO4 was added as the carrier so that BaSO4-S35 might weigh 30 mg per one Petri dish.3. Oxidation of Samples The samples to be assayed for radioactivity were subjected to wet oxidation by using concentrated HNO3 with the aid of H2O2. Complete recovery of sulfur from the tissues by means of such wet oxidation may be impossible as stated by Evans (2). In our preliminary experiments, however, more than 95 per cent of S35 of TPD was recovered. It appears, therefore, that the process of wet oxidation is an ade quate method for the estimation of TPD-S35 in the tissues.4. Chemical Estimation TPD was chemically measured according to Fujiwara after conversion into thiamine, which was then determined as thiochrome after permutit adsorption.
RESULTS
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