EFFECT OF OCTREOTIDE ON CATECHOLAMINE PLASMA-LEVELS IN PATIENTS WITH CHROMAFFIN CELL TUMORS

Many chromaffin cell tumors contain somatostatin (SS), and most of the m are receptor-positive by in vitro autoradiography and by in vivo adm inistration of radiolabeled SS analogs. We evaluated the effect of a 2 -hour infusion of 50 mu g octreotide on plasma norepinephrine (NE) and epinephrine (E) levels in 6 patients with chromaffin cell tumors. To ascertain the biological activity of octreotide, plasma insulin levels were also measured. Infusion of octreotide was followed in all the pa tients but 1 by a progressive decrease of plasma NE levels. On the ave rage, plasma NE decreased significantly during octreotide administrati on, halving its baseline levels at the end of the infusion (51.3+/-11. 46%, p<0.05) and rising again slowly thereafter. A slight reduction of plasma E levels was also recorded at the end of octreotide infusion ( 76.1+/-13.77% of baseline, NS) with a prompt return of hormone concent rations to preinfusion values. During octreotide administration, plasm a insulin displayed an early and steep fall (49.7+/-4.61% of baseline, p<0.03, at 60 min) with a tendency to escape from inhibition before t ermination of the infusion. In 5/6 patients, 2 of whom were normotensi ve before the study and 1 the day of the test, blood pressure did not change during octreotide infusion. In the other patient, blood pressur e fell from baseline values of 160/100 to 120/70 mm Hg at 120 min and rebounded to 205/100 mm Hg at 240 min. In conclusion, the short-term a dministration of low-dose octreotide is capable of lowering NE levels, though with no consistent effect on blood pressure, in patients with chromaffin cell tumors. The effect of sustained treatment with octreot ide seems to be worth investigating.