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Revista Medicina Nuclear Alasbimn Journal, Year 5, Nº 19

 

 

 

 

 

 

 
Alasbimn Journal, Year 5, Nº 19, January 2003


Análogos de Somatostatina Marcados con 99mTc

RESUMEN

El objetivo del presente trabajo es el estudio biológico y radioquímico de dos análogos de la somatostatina, el péptido RC-160 y el Tyr3-Octreotide (TOC), marcados con 99mTc por método directo e indirecto usando como quelantes mercapto acetil triglicina (MAG3) e hidrazinonicotinamida (HYNIC) respectivamente.

Se realizó la síntesis del benzoil MAG3-RC-160 y del HYNIC-Tyr3-Octreotide los cuales se marcaron con 99mTc obteniéndose purezas radioquímicas mayor que 70% y mayor que 95% respectivamente.

Se realizaron biodistribuciones en ratas Wistar normales y los resultados se correlacionaron con los datos cromatográficos y de unión a proteinas, encontrándose que a menor lipofilicidad de los complejos se incrementaba la excreción renal.

Se realizaron ensayos de unión a receptores utilizando como fuente de los mismos membranas de corteza de cerebro de rata.

Los mejores resultados se obtuvieron con el conjugado de HYNIC-TOC marcando con tricina como coligando.

ABSTRACT

The aim of the present work was to study the biological and radiochemical behaviour of two somatostatin analogues, the RC-160 and Tyr3Octreotide(TOC) peptides when labeling with 99mTc by an indirect method using S-Benzoyl- mercaptoacetyl triglycine (MAG3) and hydrazinonicotinamide (HYNIC) as chelating agents. The synthesis of RC160 with S-Benzoyl MAG3 and TOC with HYNIC, for labeling with 99mTc are also described. The conjugates were prepared on a small scale and labeled with the radionuclide using tricine as coligands for HYNIC conjugates. Chromatohraphic studies were performed using an HPLC system and radiochemical purities higher than 75% and 95% were obtained respectively. Biodistributions studies in normal Wistar rats were performed and results were correlated with chromatographic and protein binding properties. Lower lipophilicity of the labeled conjugates resulted in a higher renal excretion. HYNIC-TOC complex showed promising results when labeling with 99mTc using tricine as coligand although higher stability should be found for ternary coligands compared to tricine.

Keywords: somatostatin analogues; labelled Tyr3Octreotide; indirect labeling

 

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