Kinetic study of benzyl [1-14C]acetate as a potential probe for astrocytic energy metabolism in the rat brain: Comparison with benzyl [2-14C]acetate

Brain uptake of [14C]acetate has been reported to be a useful marker of astrocytic energy metabolism. In addition to uptake values, the rate of radiolabeled acetate washout from the brain appears to reflect CO2 exhaustion and oxygen consumption in astrocytes. We measured the time–radioactivity curves of benzyl [1-14C]acetate ([1-14C]BA), a lipophilic probe of [1-14C]acetate, and compared it with that of benzyl [2-14C]acetate ([2-14C]BA) in rat brains. The highest brain uptake was observed immediately after injecting either [1-14C]BA or [2-14C]BA, and both subsequently disappeared from the brain in a single-exponential manner. Estimated [1-14C]BA washout rates in the cerebral cortex and cerebellum were higher than those of [2-14C]BA. These results suggested that [1-14C]BA could be a useful probe for estimating the astrocytic oxidative metabolism. The [1-14C]BA washout rate in the cerebral cortex of immature rats was lower than that of mature rats. An autoradiographic study showed that the washout rates of [1-14C]BA from the rat brains of a lithium–pilocarpine-induced status epilepticus model were not significantly different from the values in control rat brains except for the medial septal nucleus. These results implied that the enhancement of amino acid turnover rate rather than astrocytic oxidative metabolism was increased in status epilepticus.

Autoradiographic study of 3H colchicine binding in synchronously dividing cells of antheridial filaments of Chara vulgaris L. during successive stages of development

The intensity of ³H colchicine binding was investigated autoradiographically as a marker of an amount of the microtubule subunits during interphase and mitosis in synchronously dividing 4-, 8-, 16- and 32-celled antheridial filaments of <i>Chora vulgaris</i>. These cells were incubated with 3H colchicine in vivo or after fixation. The radioactivity of cells in the successive generations of antheridial filaments diminishes, similarly as the surface of cytoplasm and intensity of protein synthesis. During interphase the intensity of ³H colchicine binding is proportional to the increase of cytoplasmic surface; the highest increase of radioactivity occurs in G₂. During mitosis the increase of radioactivity continues in prophase; the highest radioactivity was found in prophase and telophase cells, the lowest in anaphase cells; a comparatively pronounced radioactivity is visible in metaphase. Radioactivity in posttelophase, as estimated per one daughter cell, is approximately one half of that of the mother cells in telophase of the previous generation suggesting the reutilization of microtubule proteins in the next mitotic cycle.