Baba Akemichi

Gonadectomy changes the pituitaiy-adrenocortical response in mice to S-HT1A receptor agonists

Abstract The effects of 5-HT 1A receptor agonists such as 8-hydroxy-2-(ui-n-propylamino)tetralin (8-OH-DPAT), BP 554 and buspirone on the serum corticosterone level were significantly more pronounced in female than in male mice. A similar sex difference was observed for the effect of 8-OH-DPAT on the piasma ACTH level. Pretreatment with proadifen, an inhibitor of microsomal drug-metabolizing enzymes, did not affect the sex difference in the effect of 8-OH-DPAT. The corticosteione response to 8-OH-DPAT in female mice was attenuated by ovariectomy. The effect of 8-OH-DPAT in ovariectomized mice was enhanced by chronic estradiol and the enhancement was blocked by testosterone. In male mice the corticosterone response to 8-OH-DPAT increased at 5 weeks after castration but had not changed at 2 weeks. Chronic estradiol enhanced the corticosterone response to 8-OH-DPAT in castrated mice. There was no difference between sexes in [ 3 H]8-OH-DPAT binding to membranes and in the contents of 5-HT and 5-hydroxyindoleacetic acid in the hypothalamus. Accumulation of 5-hydroxytryptophan after decarboxylase inhibition in the hypothalamus was however greater in female than in male mice.

Assay of phospholipase A2 activity of synaptic membranes using a phospholipid transfer protein: stimulation by depolarization

A phospholipid transfer protein from bovine liver was used to transfer exogenous ([14C]linoleoylphosphatidylethanolamine [14C]linoleoyl PE) into synaptic membranes and synaptosomes without modifying the lipid compositions in order to study the intrinsic activity of phospholipase A2 of the preparations. Results were compared with the conventional method in which the substrate was simply dispersed with the enzyme preparations. Liberation of [14C]linoleic acid from [14C]linoleoyl PE-preloaded synaptic membranes by the transfer protein continued almost linearly over 60 min of incubation in the presence of Ca2+. The dose-response curve of Ca2+ for the activity of phospholipase A2 obtained in the present method was slightly shifted to the left in comparison with the conventional method: Ca2+ even at the concentration of 100 microM significantly enhanced the enzyme activity. Requirement of Ca2+ for the reaction is more specific in the present method than in the conventional one. When synaptosomes were prelabeled with [14C]linoleoyl PE by the transfer protein, the liberation of [14C]linoleic acid during the incubation at 37 degrees C increased linearly over 2 min. The liberation of [14C]linoleic acid was significantly enhanced in the presence of 56 mM KCl, 50 microM veratridine and 50 microM calcium ionophore A23187. These agents did not stimulate the reaction in the absence of Ca2+.

Postnatal development of thiamine metabolism in rat skeletal muscle

Abstract 1. 1. The activities of 2-oxoglutarate dehydrogenase, transketolase, thiamine pyrophosphokinase and thiamine triphosphatase and the concentrations of thiamine phosphates were almost the same between rat extensor digitorum longus and soleus muscles at 2 weeks of age. 2. 2. These enzyme activities changed after 3 weeks of age in a different way depending on the muscle phenotype. 3. 3. Thiamine diphosphate level and the activity of 2-oxoglutarate dehydrogenase increased only in soleus muscle and thiamine triphosphate level increased only in extensor digitorum longus during development.