Hormone-mediated Ca2+ transients in isolated renal cortical thick ascending limb cells

Abstract

Peptide hormones control salt reabsorption in cortical thick ascending limb (cTAL) cells of the loop of Henle. These agonists act, in part, through alterations on intracellular Ca2+ ([Ca2+]i). Primary cell cultures were prepared from porcine kidneys using a double antibody technique (goat antihuman Tamm-Horsfall and rabbit antigoat IgG antibodies). [Ca2+]i was determined in single cells with fluorescent techniques using fura-2. Parathyroid hormone (PTH) and arginine vasopressin (AVP) transiently increased [Ca2+]i in a dose-dependent manner. [Ca2+]i maximally increased from 85 +/- 5 nmol/l to 608 +/- 99 nmol/l with PTH, 10(-6) M, and to 766 +/- 162 nmol/l with AVP, 10(-7) M. The increment in [Ca2+]i by both hormones was by intracellular Ca2+ release and entry through plasma membrane Ca2+ channels. 8-Bromo-adenosine-3',5'-cyclic monophosphate (8-BrcAMP), 10(-4) M, increased [Ca2+]i (basal 83 +/- 3 to 427 +/- 121 nmol/l) but only from internal sources as nifedipine (10 mumol), ([Ca2+]i changes: 86 +/- 4 to 390 +/- 29 nmol/l) and removal of bath Ca/+o, ([Ca2+]i changes: 84 +/- 6 to 517 +/- 142 nmol/l), were without effect on agonist-induced [Ca2+]i. Thapsigargin, 1.5 mumol, completely abolished the AVP- and cyclic adenosine monophosphate-(cAMP)-induced Ca2+ transients, and partially inhibited PTH-mediated Ca2+ transients by about 50%. Pretreatment with 8-BrcAMP inhibited the PTH and AVP responses likely through depletion of cAMP-sensitive Ca2+ stores. Activation of protein kinase C (PKC) with phorbol esters inhibited PTH and AVP responses and 8-BrcAMP-induced [Ca2+]i transients.(ABSTRACT TRUNCATED AT 250 WORDS)