Effect of angiotensin II on calcium reabsorption by the luminal membranes of the nephron

Maisonneuve-Rosemont Hospital; Guy-Bernier Research Center; and University of Montreal, Montreal, Quebec, Canada H1T 2M4 In the rat and the rabbit, a number of studies have reported the effects of angiotensin II (ANG II) on Na + reabsorption by the proximal (PT) and distal (DT) convoluted tubules of the kidney. The aim of the present study was to examine the effect of ANG II on Ca 2+ uptake by the luminal membranes of the PT and DT of the rabbit. Incubation of PT and DT with 10 12 M ANG II enhanced the initial Ca 2+ uptake in the two segments. Dose-response experiments revealed, for Ca 2+ as well as for Na + transport, a biphasic action with a maximal effect at 10 12 M. Ca 2+ transport by the DT luminal membrane presents a dual kinetic. ANG II action influenced the high-affinity Ca 2+ channel, increasing maximal velocity from 0.72 ± 0.03 to 0.90 ± 0.05 pmol · µg 1 · 10 s 1 ( P