Activation of rat thymocytes selectively upregulates the expression of somatostatin receptor subtype-1

Somatostatin and other neuropeptides are known to modulate the proliferative capacity of immune cells. In the present study, we investigated the expression of Somatostatin receptor (SSTR) subtypes on rat thymocytes. RT-PCR analysis of fresh thymocytes showed significant levels of transcripts for the SSTR2 whereas transcripts for the SSTR1 and SSTR3 were not detectable. Interestingly, when the thymocytes were activated with low concentration of Phytohemagglutinin and interleukin 1, the transcript for SSTR1 was markedly increased. Lymphokine induced activation of thymocytes selectively upregulated the SSTR1 since, transcripts for SSTR2 remained the same after activation and SSTR3 was not detectable. PCR amplified fragment of SSTR1 from the activated thymocytes showed identical sequence to the rat brain receptor. The physiological significance of the increase of SSTR1 mRNA in thymocytes after activation remains to be elucidated but it may be possible that these two different subsets of receptors (SSTR1 and SSTR2) are involved in the modulation of thymocyte proliferation and differentiation.