Accumulation of radioactivity in rat brain and peripheral tissues including salivary gland after intravenous administration of 14C-D-aspartic acid

Abstract

After the intravenous administration of 14C-D-aspartic acid (Asp) into Sprague-Dawley rats (male, 7-week-old), the distribution and elimination of radioactivity was investigated by the whole body autoradiography. High radioactivities were detected in pineal gland, pituitary gland and salivary gland at 30 min after administration. The other tissues detected were liver, lung, adrenal gland, pancreas and spleen where D-Asp was reported to occur naturally. After 24 hr, the radioactivities were still detected at high levels in the pineal, pituitary and salivary glands. The data suggested the natural occurrence of D-Asp in salivary gland. After careful examination utilizing fluorescent derivatization and chiral separation by high-performance liquid chromatography, the presence of D-Asp was, for the first time, demonstrated in salivary gland in situ, the concentration of which was 7.85±1.0 nmol/g. The administration of 14C-L-Asp was also carried out. The data suggested that D-Asp in the circulating blood is one of the sources of the tissue D-Asp.