Antidiuretic hormone acts via V1 receptors on intracellular calcium in the isolated perfused rabbit cortical thick ascending limb.
The effect of antidiuretic hormone [( Arg]vasopressin, ADH) on intracellular calcium activity [Ca2+]i of isolated perfused rabbit cortical thick ascending limb (cTAL) segments was investigated with the calcium fluorescent dye fura-2. The fluorescence emission ratio at 500-530 nm (R) was monitored as a measure of [Ca2+]i after excitation at 335 nm and 380 nm. In addition the transepithelial potential difference (PDte) and transepithelial resistance (Rte) of the tubule were measured simultaneously. After addition of ADH (1-4 nmol/l) to the basolateral side of the cTAL R increased rapidly, but transiently, from 0.84 +/- 0.05 to 1.36 +/- 0.08 (n = 46). Subsequently, within 7-12 min R fell to control values even in the continued presence of ADH. The increase in R evoked by the ADH application corresponded to a rise of [Ca2+]i from a basal level of 155 +/- 23 nmol/l [Ca2+]i up to 429 +/- 53 nmol/l [Ca2+]i at the peak of the transient, as estimated by intra- or extracellular calibration procedures. The electrical parameters (PDte and Rte) of the tubules were not changed by ADH. The ADH-induced Ca2+ transient was dependent on the presence of Ca2+ on the basolateral side, whereas luminal Ca2+ had no effect. d(CH2)5[Tyr(Me)2]2,Arg8vasopressin, a V1 antagonist (Manning compound, 10 nmol/l), blocked the ADH effect on [Ca2+]i completely (n = 5). The V2 agonist 1-desamino-[D-Arg8]vasopressin (10 nmol/l, n = 4), and the cAMP analogues, dibutyryl-cAMP (400 mumol/l, n = 4), 8-(4-chlorophenylthio)-cAMP (100 mumol/l, n = 1) or 8-bromo-cAMP (200 mumol/l, n = 4) had no influence on [Ca2+]i. The ADH-induced [Ca2+]i increase was not sensitive to the calcium-channel blockers nifedipine and verapamil (100 mumol/l, n = 4). We conclude that ADH acts via V1 receptors to increase cytosolic calcium activity transiently in rabbit cortical thick ascending limb segments, possibly by an initial Ca2+ release from intracellular stores and by further Ca2+ influx through Ca2+ channels in the basolateral membrane. These channels are insensitive to L-type Ca2+ channel blockers, e.g. nifedipine and verapamil.
Nitschke
R
R
Physiologisches Institut, Albert-Ludwigs-Universität, Freiburg, Federal Republic of Germany.
Fröbe
U
U
Greger
R
R
D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D000818:Animals; D001127:Arginine Vasopressin / Q000031:analogs & derivatives / Q000494:pharmacology*; D001692:Biological Transport / Q000187:drug effects; D003994:Bucladesine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism* / Q000493:pharmacokinetics; D003894:Deamino Arginine Vasopressin / Q000494:pharmacology; D005110:Extracellular Space / Q000378:metabolism; D005260:Female; D016257:Fura-2; D007686:Kidney Tubules, Distal / Q000378:metabolism*; D008297:Male; D009543:Nifedipine / Q000494:pharmacology; D010477:Perfusion; D011817:Rabbits; D011956:Receptors, Cell Surface / Q000187:drug effects / Q000502:physiology*; D015398:Signal Transduction / Q000187:drug effects; D014700:Verapamil / Q000494:pharmacology
D011956:Receptors, Cell Surface; D001127:Arginine Vasopressin; D015124:8-Bromo Cyclic Adenosine Monophosphate; D003994:Bucladesine; C025043:vasopressin, 1-(1-mercaptocyclohexaneacetic acid)-2-(O- methyl-L-tyrosine)-8-L-arginine-; D014700:Verapamil; D003894:Deamino Arginine Vasopressin; D009543:Nifedipine; D002118:Calcium; D016257:Fura-2