INHIBITORY EFFECT OF THE SOMATOSTATIN ANALOG OCTREOTIDE ON RAT PITUITARY-TUMOR CELL (GH3) PROLIFERATION INVITRO

The effects of somatostatin-14 (SS-14) and the somatostatin-analog octreotide (SMS 201-995, Sandostatin) on proliferation of GH₃ pituitary tumor cells were investigated in vitro. SMS 201-995 exerted a significant, but transient, inhibition on GH₃ cell growth which reached a maximum at 24 h and was no longer detectable at 48 h. The concentration that evoked the strongest inhibitory effect was 10 nM SMS 201-995, while lower and higher doses resulted in a less pronounced effect. The inhibitory effect SMS 201-995 exerted on cell proliferation was associated with a dose- and time-related reduction in both c-myc and c-fos mRNA levels. SS-14 had no noteworthy influence on either cell proliferation or c-myc and c-fos protooncogene expression. These data demonstrate that SS-analogs transiently inhibit pituitary tumor cell proliferation in vitro.