Μελέτη των θέσεων δέσμευσης του L-γλουταμικού οξέος σε φυσιολογική και ατροφική ανθρώπινη παρεγκεφαλίδα: Συμβολή στη μελέτη της ελαιογεφυρο-παρεγκεφαλιδικής ατροφίας

The binding kinetics, pharmacological properties, ontogeny and localization of Cl⁻ dependent and/ CI⁻independent L-glutamate binding sites were studied in membrane preparations and sections of human cerebellum. Furthermore L-glutamate binding have been solubilized from the same membrane preparations using different detergents, as CHAPS, Zwittergent 3-12 and Digitonin. At last, a comparative study of L-[³H] glutamate binding sites was done between normal and OPCA (olivocerebellar atrophy) human cerebellum. The results of the above studies are as follows: 1. One binding component was found in both CI⁻ dependent and -independent conditions for L-glutamic acid with Kd values in the order of 150Χ10⁻⁹Μ. Hill plots of these data were linear with Hill coeficient equal to 1.0. Chloride ions provoked a significant increase of L-glutamate binding, with ratio of Cl⁻-dependent/-independent binding sites about 4/1. L-glutamate, L-aspartate, quisqualate, L-homocysteic and ibotenic acid were potent inhibitors of L-[³H] glutamate binding, whereas D,L-APB, kainic acid and NMDA were weak inhibitors. L-[³H] glutamate binding showed a significant degree of stereoselectivity toward L- and D-isomers of glutamate and aspartate. With the exception of quisqualate, all amino acid analogue used did not show significant differences in their affinities of inhibition between Tris-HCl and Tris-acetate buffer. Under Cl⁻ dependent conditions the inhibition curve of quisqualate was biphasic (IC50=6.30nM and 15,85μΜ), whereas under Cl⁻-independent conditions was monophasic with IC50 value very similar to the low affinity site observed in Tris-HCl buffer. The ontogeny of L-glutamic acid binding sites in human cerebellum showed that no significant changes of F' values were observed with age, whereas the highest Bmax value was observed at the age of 1 year. Autoradiography revealed L-glutamate binding sites in both granule cell and molecular layers of human cerebellum. In the presense of Cl⁻ ions an increase of about 2,5 times was observed in the molecular layer, whereas in the absence of Cl⁻ ions L-glutamate binding was more pronouced in the granule cell layer. 2. Solubilization experiments showed that Zwittergent 3-12 was more effective in solubilizing L-glutamate binding sites than CHAPS or digitonin. 3. In OPCA cerebellar a very significant decrease of L-[³H] glutamate specific binding (Bmax) was observed in both CI⁻-dependent and-independent conditions, whereas Kd values were found unchanged. The pharmacological properties of L-[³H] glutamate binding sites of OPCA cerebellar tissues were similar to those of normal cerebellum. [³H]-QNB binding expressed in fmoles/mg protein, did not show significant differences between normal and OPCA cerebella.

Grantor dc:publisher

University of Patras

Year dc:date

1990

Authors dc:creator

• Tsiotos, Panagiotis
• Τσιώτος, Παναγιώτης

• L-γλουταμικό οξύ
• Ανθρώπινη παρεγκεφαλίδα
• Ελαιο-Γεφυρο-Παρεγκεφαλιδική ατροφία
• Θέσεις δεσμεύσεις
• Binding sites
• HUMAN CEREBELLUM
• L-glutamic acid
• Olivo-Pontino-Cerebellar atrophy
• Ιατρική και Επιστήμες Υγείας
• Βασική Ιατρική
• Medical and Health Sciences
• Basic Medicine

Language dc:language

gre

Identifier

10.12681/eadd/1389

OAI identifier oai:identifier

oai:10442/1389