Secretin and portal blood flow

Using a duplex Doppler technique, we investigated the effect of low doses of secretin on the portal blood flow. In eight healthy volunteers successive intravenous secretin infusions of 0, 8, and 32 pmol x kg-1 x h-1 resulted in proportional increases in plasma secretin levels. The portal venous flow, however, was unaffected. A bolus injection of 930 pmol of secretin caused plasma secretin levels to increase 100-fold, whereas blood flow in the portal vein increased only by a factor three. This suggests that secretin in the present dose range is of no quantitative importance as a regulator of portal venous flow under physiologic conditions.