ABSENCE OF APOPTOSIS IN SOMATOTROPINOMAS TREATED WITH OCTREOTIDE

Octreotide is a potent agonist of somatostatin that lowers the serum l evel of growth hormone (GH), and reduces the size of somatotropinomas. However, the detailed mechanism of shrinkage of this tumour is not kn own. We, therefore,evaluated 11 patients with somatotropinomas who wer e treated with octreotide 300 mu g/day for 2-5 weeks to observe the mo rphological changes in the tumour using electron microscopy and the im munocytochemical study of apoptosis using polyclonal anti-single stran ded DNA. Findings were compared with those obtained with bromocriptine treatment (10 mg/day, 2 weeks) of 5 patients with somatotropinomas, a nd 11 patients who received no preoperative treatment (control group). The octreotide group showed neither increase in stromal tissue nor fe ll death. The size of tumour cells appeared to be slightly reduced. No typical apoptotic bodies were seen on the electron micrographs. The a poptotic index in the octreotide group (0.40 +/- 0.60%; mean +/- SD) r esembled that in the control group (0.81 +/- 0.79%). Ln contast, the b romocriptine group showed some cell death and an increase in stromal t issue. The bromocriptine group also showed the apoptotic index which ( 20.1 +/- 14.8%) was significantly higher than that of the control grou p (0.8 +/- 0.79%). Thus, octreotide did not induce apoptosis in somato tropinomas despite the presence of tumour shrinkage. Because of the la ck of fibrosis observed in the octreotide-treated tumours, the preoper ative administration of octreotide may help to improve the outcome of the transsphenoidal operation.