REGULATION OF PELVIC PATCH WATER-FLOW IN BUFO-MARINUS - ROLE OF BLADDER VOLUME AND ANG-II

This report examines the importance of bladder volume in regulating cu taneous water uptake (J(v), cm3.cm-2.s-1 x 10(-7)) across the ventral pelvic patch and examines the role of angiotensin II (ANG II) and circ ulation as the regulatory mechanism. J(v) in empty-bladder Bufo marinu s (bladder volume 3.89 +/- 1.49%, n = 7) was 1,671 +/-68 (n = 7). Inje ction of Ringer solution into the bladder (12.8 +/-2.2%, n = 7) decrea sed J(v) to 1,025 +/- 202 (n = 7). ANG II injected into toads with fil led bladders increased J(v) in a dose-dependent manner. At 5 mug/100 g toad J(v) increased by 136 +/- 63 (n = 6), at 50 mug/100 g toad by 43 2 +/- 82 (n = 7), and at 200 mug/100 g toad by 620 +/- 142 (n = 5). Sa ralasin (200 mug/100 g toad) completely inhibited the response to ANG II (50 mug/100 g toad) and at 1 mg/100 g toad decreased J(v) in empty- bladder toads. These experiments indicate that 1) bladder volume parti cipates in the regulation of J(v) in the ventral pelvic patch; 2) ANG II increases the J(v) in toads with full bladders; 3) saralasin inhibi ts the high J(v) in empty-bladder toads; 4) the high J(v), associated with an empty bladder, requires an intact circulation to be maintained ; 5) without an intact circulation, the high water flow associated wit h an empty bladder causes the Na+ content of the tissue in the ventral patch to be reduced; and 6) ANG II causes only a minimal increase in water permeability in the isolated pelvic patch skin.