Angiotensin II alters blood flow distribution in amphibians

In toads, angiotensin II (ANG II) induces the water absorption response (WR) during which the seat patch (pelvic + inner-thigh skin) is pressed to a wet substrate from which water flows osmotically into the animal. Since ANG II is a potent vasoconstrictor, it has the potential to redistribute blood flow. To determine the regional circulatory effects of ANG II, we used microsphere methods to measure relative changes in blood flow to several skin regions and other organs before and after ANG II administration in terrestrial toads and aquatic bullfrogs. In toads, after ANG II administration, seat patch and bladder blood flow increased by and 264.2% +/- 197.6% and 287.2% +/- 86.7%, respectively (P < 0.05), while dorsal and pectoral skin flow decreased by and 48.0% +/- 19.4% and 21.3% +/- 25.4%, respectively (P < 0.05). In bullfrogs, ANG II caused no significant changes in blood flow. Our results support our hypothesis that, in toads, ANG II increases and decreases blood flow to regions of the body associated with water gain and water loss, respectively.