Fasting and meal-stimulated plasma levels of neurotensin in obese patients after jejunoileal bypass with 3:1 or 1:3 jejunoileal ratio.

The functional role of the jejunum and ileum with regard to peripheral plasma levels of intact neurotensin and NH2-terminal immunoreactivity of neurotensin was studied by using jejunoileal bypass as a model. Plasma levels were measured by radioimmunoassay before and after jejunoileal bypass randomized to different jejunoileal ratios. Seven patients were studied before bypass surgery and 28 were examined after end-to-side jejunoileal bypass with 50 cm intestine in continuity and a 3:1 or 1:3 ratio between the length of the jejunal and ileal segments. Fasting levels of intact neurotensin were unchanged by surgery, whereas levels of NH2-terminal immunoreactivity were higher in bypass patients with a long ileal segment (37.5 cm) than in unoperated patients and in those with a short ileal segment (12.5 cm). Meal-stimulated levels of intact neurotensin were higher after 1:3 than 3:1 jejunoileal bypass. The levels of NH2-terminal immunoreactivity in patients with a short ileal segment and in controls were lower than in patients with a long ileal segment. The results show that postprandial levels of both intact neurotensin and NH2-terminal immunoreactivity are related to the length of the functioning ileum and that even a difference in length of 25 cm is reflected in the circulating levels of neurotensin.