Immunomodulatory action of somatostatin.

The influence of somatostatin (SST) on spontaneous proliferation and cyclic AMP level in mouse spleen lymphocytes and on inhibition of human leukocyte migration was studied. The rate of [3H]thymidine incorporation was used as an index of proliferation. It was found that lower concentrations of SST/10(-9) and 10(-8)M, inhibited the splenocyte proliferation. In contrast, a higher SST concentration, 10(-7)M, exerted a stimulatory effect. SST in concentrations from 10(-9) to 10(-6)M did not influence cyclic AMP levels in mouse splenocytes; a significant decrease of cyclic AMP was found after the exposure to superactive SST analog RC-102-2H in concentrations 10(-8) and 10(-7)M. SST, 10(-7)M, and RC-102-2H, 10(-7)M, significantly enhanced the migration inhibition of human leukocytes induced by the exposure of leukocytes to cardiac antigen or phytohemagglutinin. The data provide evidence for an immunomodulatory action of SST.