The effect of the gastrointestinal hormones on colonic mucosal blood flow

The effect of intravenous administration of various gastrointestinal hormones or peptides on the colonic mucosal blood flow was investigated by a reflex spectrum apparatus (TS-200, Sumitomo Denko Co). Various gastrointestinal hormones (pentagastrin, secretin, substance P, vasoactive intestinal polypeptide) were administered via the femoral vein at different doses. The hormones were administered over 30 minutes using a chronofuser at a rate of 0.1 ml/min. Serial measurements of cecal mucosal blood flow were performed. Saline was administered to the control group. 1) Pentagastrin was administered at doses of 1μg/kg/hr, 50μg/kg/hr, 100μg/kg/hr, and 200μg/kg/hr. Cecal mucosal blood flow decreased when the dose of pentagastrin was increased. The intravascular supply of oxygen also decreased in a dose dependent manner. Each dose of the gastrointestinal hormone caused a reduction in blood pressure. 2) Secretin was administered at doses of 5μg/kg/hr, 50μg/ kg/hr, and 100μg/kg/hr. Each tested dose of this gastrointestinal hormone acted to maintain cecal mucosal blood flow. The blood pressure remained unchanged throughout the experiment. 3) Substance P was administered at doses of 1μg/kg/hr and 5μg/kg/hr. Cecal mucosal blood flow and the intravascular oxygen supply increased after administration of this gastrointestinal hormone. The blood pressure decreased transiently at the start of administration, but later gradually returned to the baseline values. 4) Vasoactive intestinal polypeptide (VIP) was administered at doses of 1μg/kg/hr, 5μg/kg/hr, and 10μg/kg/hr. VIP caused the cecal mucosal blood flow to increase in a dosedependent manner. The intravascular oxygen, supply also increased signific antly after administration of this gastrointestinal hormone. The blood pressure initially de creased after administration of each test dose of VIP, after which it gradually started to increase. 5) To identify the factors responsible for the increase in cecal mucosal blood flow at the start of VIP administration at a dose of 5μg/kg/h of VIP, the blood concentrations of VIP, cyclic AMP, phospholipase, prostaglandin E_2, prostaglandin: E, and 6 keto-prostaglandin:F_1α were examined at regular intervals. However, no significant changes with regard to these substances were noted