HEPATIC PRODUCTION OF GLOMERULAR PRESSURE SUBSTANCE IN TOAD (BUFO ARENARUM)

Isolated toad kidneys were alternately perfused with normal plasma and plasma that had circulated through the isolated hind legs or liver at low or at high rates of flow. Plasma that had circulated through a toad's hind legs or liver at low flow rates produced no change in glomerular pressure index (GPI) though it increased renal plasma flow rate (RPF), probably through the action of a vasodilator substance. Plasma circulated through a liver at a high flow rate produce an increase in the GPI and in RPF. This suggests release of a glomerular pressure substance (GPS) by the liver perfused at high flow rates. Estimated hepatic plasma flow (EHPF) was measured by the bromsulphalein extraction method. Simultaneously, the arterial pressure (AP) and glomerular pressure index (GPI) were registered. Experiments were performed in normal animals and in animals whose blood volume had been expanded with 3 ml of blood. Expansion of blood volume produced an increase in EHPF as well as in GPI, while AP remained unchanged. A good correlation exists between GPI and EHPF. The evidence supports the conclusion that the liver produces a glomerular pressure substance (GPS) whose release is enhanced by an increase in hepatic plasma flow. © 1969.