Somatostatin receptor subtypes in human astrocytes and gliomas: Influence of cultivation process

Summary

Expression of somatostatin receptors was investigated on normal human astrocytes and human glial tumours. All cultivated glial cells and gliomas, directly embedded in paraffin were immunopositive for the astrocytic marker glial fibrillary acidic protein. Moreover, somatostatin-binding sites could be visualized on all cell types by affinity labelling with a somatostatin-gold conjugate. Thereby, the normal astrocytes showed a fine, stippled pattern of the conjugate all over the cell surface wheras the tumourous cells had a more thread-like pattern preferentially on the cell processes. The transcripts of the different somatostatin receptor subtypes were detected by reverse transcription — poymerase chain reaction (RT-PCR) with oligonucleotides specific for five human somatostatin receptor subtypes (SSTRs). Normal astrocytes expressed SSTR-1, (SSTR-2) and SSTR-4 specific transcripts, glioma cells showed an overexpression of SSTR-2 compared to normal astrocytes (relative to equal intensities for β-actin amplificates). This overexpression of SSTR-2 transcript could be detected in cultivated tumour glial cells as well as in solid gliomas. Thus the cultivation process had no influence on the individual SSTR-2 expression on normal and tumourous cells.