These studies were designed to examine the cellular messenger that mediates the action of angiotensin II on fluid transport (J(v)) in the rabbit proximal tubule. We measured the effects of angiotensin II on J(v), activation of adenylate cyclase, and the concentration of cytosolic free calcium (Ca(i)) in the rabbit proximal tubule. In nine rabbit proximal convoluted tubules (PCT), angiotensin II, 10-8 M and 10-6 M, decreased J(v) by 18 and 25%, P < 0.05. In eleven rabbit proximal straight tubules (PST), 10-8 and 10-6 M angiotensin II decreased J(v) by 20 and 23%, P < 0.02. Angiotensin II did not affect lumen-to-bath phosphate fluxes in PCT or PST, and it did not activate adenylate cyclase in PST. In a preparation of proximal tubules (PCT and PST) loaded with aequorin, angiotensin II, 10-8 and 10-6 M, transiently increased Ca(i) by 13 and 32%, P < 0.001. We propose that Ca(i) surges, activated by angiotensin II, are part of a cellular message that inhibits J(v) in the rabbit proximal tubule.
|Title of host publication||American Journal of Physiology - Renal Fluid and Electrolyte Physiology|
|State||Published - 1987|
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