SMALL-INTESTINAL MICROCIRCULATORY EFFECTS OF OCTREOTIDE

Somatostatin and its analogue, octreotide acetate, are thought to decr ease mesenteric blood flow; however, it is unknown whether the decreas e occurs at the central, regional, or microvascular level. We hypothes ized that the circulatory effects of octreotide are regulated at the m icrovascular level. Changes in superior mesentery artery (SMA) flow in response to octreotide were measured with a perivascular ultrasonic f low probe. In separate experiments, the jejunal microcirculatory effec ts of octreotide were studied using in vivo videomicroscopy. After acc rual of baseline hemodynamic and microcirculatory data, animals were r andomized to control or treatment (10 mu g/kg octreotide) iv groups. M easurements were made every 15 min during the infusion and for 90 min after the completion of the infusion. Results are expressed as means /- SEM. Intravenous infusion of octreotide caused no significant chang e in arterial pressure, cardiac index, or systemic vascular resistance index in either group in either set of experiments. A statistically s ignificant decrease in heart rate (9%) occurred in the control group o f animals undergoing SMA flow measurement. SMA flow did not change sig nificantly with infusion of octreotide. In contrast, jejunal first-ord er arteriole flow increased to 117.9 +/- 9.7% of baseline (P < 0.05) i n the absence of significant changes in microvessel diameters. This wa s due to an increase in centerline red cell velocity (116 +/- 5% of ba seline, P < 0.05). We conclude that octreotide increases jejunal first order arteriole flow by mechanisms that are regulated at the microcir culatory level. (C) 1994 Academic Press, Inc.