title: Involvement and source of calcium in volume regulatory decrease of collapsed proximal convoluted tubule.
abstract: We examined the role of Ca2+ in the volume regulatory decrease (VRD) of rabbit collapsed proximal tubules. Reduction of bath osmolality by 125 mosmol/kgH2O led to an initial cell swelling of 62.3 +/- 7.5% followed by a partial regulatory phase bringing cell volume to a value of 13.3 +/- 2.9% above control (n = 5). This swelling was accompanied by a transient intracellular Ca2+ ([Ca2+]i) increase from 174 +/- 33 to 306 +/- 67 nM (P < 0.05, n = 8). In the same condition, but in absence of extracellular Ca2+ ([Ca2+]e) [1 mM ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA)], VRD following hypotonic shock was identical to that observed in presence of [Ca2+]e (n = 5), and [Ca2+]i increased transiently from 136 +/- 29 to 161 +/- 31 nM (P < 0.05, n = 5). Addition of 100 microM 8-(N,N-dimethylamino)octyl 3,4,5-trimethoxybenzoate hydrochloride (TMB-8), an agent known to inhibit Ca2+ release from intracellular stores, did not affect the initial cell swelling (63.4 +/- 4.2%), and VRD occurred to the same extent (25.0 +/- 7.1%, n = 4), although at a lower rate. In these conditions, [Ca2+]i, which was 113 +/- 30 nM in the isotonic solution, decreased progressively to 81 +/- 20 nM over the 5-min hypotonic period (n = 5). Mere preincubation with 100 microM TMB-8 before hypotonic shock led to a VRD identical to that observed in presence of Ca2+ and absence of TMB-8 while still blocking the Ca2+ release, with cell Ca2+ decreasing progressively from 179 +/- 32 to 87 +/- 21 nM (n = 7).(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Groupe de Recherche en Transport Membranaire, Université de Montréal, Quebec, Canada.
authors.forename: S
authors.initials: S
authors.lastname: Breton
authors.forename: J S
authors.initials: JS
authors.lastname: Beck
authors.forename: J
authors.initials: J
authors.lastname: Cardinal
authors.forename: G
authors.initials: G
authors.lastname: Giebisch
authors.forename: R
authors.initials: R
authors.lastname: Laprade
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism / Q000502:physiology*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D004594:Electrophysiology; D005110:Extracellular Space / Q000378:metabolism; D005707:Gallic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D007038:Hypotonic Solutions; D007425:Intracellular Membranes / Q000378:metabolism; D007687:Kidney Tubules, Proximal / Q000166:cytology / Q000378:metabolism*; D011817:Rabbits; D012769:Shock / Q000139:chemically induced / Q000378:metabolism
chemical_list: D002121:Calcium Channel Blockers; D007038:Hypotonic Solutions; C006014:8-(N,N-diethylamino)octyl-3,4,5-trimethoxybenzoate; D005707:Gallic Acid; D002118:Calcium