DOSE-DEPENDENT STIMULATION OF INSULIN-LIKE GROWTH FACTOR-BINDING PROTEIN-1 BY LANREOTIDE, A SOMATOSTATIN ANALOG

It was recently reported that octreotide, besides its many, almost obl igatory, inhibitory actions, stimulates the release of insulin-like gr owth factor-binding protein-1. The present study sought to exclude the possibility that the inescapable preceding somatostatin analog-induce d reduction in serum insulin participated in the observed effect. We, therefore, administered sc two clinically relevant doses (5 and 80 mu g/kg) of lanreotide, another somatostatin octapeptide analog, which in duced identical 60% initial suppressions of serum insulin. In spite of this, clear dose-dependent increases in insulin-like growth factor-bi nding protein-1 were observed, starting between 1-2 h after administra tion of lanreotide, and levels were still elevated several-fold 5 h af ter administration of 80 mu g/kg lanreotide. In addition, we found tha t infusion of amino acids had no discernible effect on binding protein -1 release. The changes found in immunoreactive binding protein-1 were confirmed employing Western ligand blotting. The data indicate that t he lanreotide-induced increase in binding protein-1 levels in serum is not due to the changes in circulating insulin. The magnitude and dura tion of the increase raise the possibility that the stimulation may ha ve clinically relevant implications in somatostatin analog treatment.