Biomedical subjects

Y Yoshihara

Publications and source records attributed to Y Yoshihara.

93 records · Page 6Linked to original sources

PubMed1986

Uptake and release of kyotorphin in rat brain synaptosomes.

Uptake and release of kyotorphin (Tyr-Arg) in rat brain synaptosomes were studied. Synthetic kyotorphin was taken up into crude synaptosomes (P2), in a temperature-dependent manner. The Km and Vmax of the uptake were 1.31 +/- 0.12 X 10(-4) M and 5.9 +/- 0.5 pmol/mg protein/min, respectively. Metabolic inhibitors such as dinitrophenol and iodoacetamide and ouabain which is known as an inhibitor of Na+ dependent uptake mechanism significantly inhibited the uptake. When the synaptosomes previously preloaded with synthetic kyotorphin at 10(-4)M were exposed to high K+ medium, kyotorphin was released in a Ca2+-dependent manner. These findings support the view that kyotorphin plays a role as neurotransmitter/neuroregulator.

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PubMed1986

A putative met-enkephalin releaser, kyotorphin enhances intracellular Ca2+ in the synaptosomes.

Kyotorphin (Tyr-Arg) at 1 to 100 microM increased the intracellular [Ca2+]i, determined with Quin-II in the slice and the entry of 45Ca2+ entry into synaptosomes of the lower brain stem of the rat. These effects were not antagonized by nifedipine nor verapamil. However, since this dipeptide caused no changes on the membrane potentials of the synaptosomes, measured with Rhodamine 6G, it is suggested that the kyotorphin-induced increase in the [Ca2+]i may be due not to effects on the voltage dependent Ca2+ channels and Na+-Ca2+ exchange mechanisms caused by the changes of the membrane potentials, but to the specific receptor (kyotorphin receptor)-mediated mechanisms.

Animals↗

PubMed1985

How is kyotorphin (Tyr-Arg) generated in the brain?

Kyotorphin (Tyr-Arg) was rapidly degraded in the brain homogenates and purified membrane-bound aminopeptidase from monkey brains. The degradation of kyotorphin by these preparations was effectively inhibited by bestatin. When brain homogenates or slices were incubated with bestatin, kyotorphin was accumulated time-dependently in a rate of 1.0 or 2.1 pmol/mg protein/hr, respectively. The bestatin-induced kyotorphin accumulation was inhibited by leupeptin, p-chloromercuribenzoate, but not phenylmethylsulfonylfluoride or diisopropylphosphate. The kyotorphin accumulation was concentrated in the P2 (crude mitochondrial) fraction, particularly in the particulate or synaptosomal fraction. These findings suggest that kyotorphin may be generated in vitro from precursor proteins by membrane-bound, leupeptin-sensitive "kyotorphin converting enzymes" in close vicinity to membrane-bound aminopeptidase which rapidly degrades kyotorphin generated.

Animals↗