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Optimal concentration of cellular free calcium for AVP-induced cAMP in collecting tubules

1990; Elsevier BV; Volume: 37; Issue: 4 Linguagem: Inglês

10.1038/ki.1990.86

1523-1755

San-e Ishikawa, Toshikazu Saito,

Electrolyte and hormonal disorders

The role of Ca2+ in the cellular action of arginine vasopressin (AVP) has been demonstrated in renal papillary collecting tubule. We further examined whether an optimal concentration of cellular free Ca2+ [( Ca2+]i) exists for AVP-induced cAMP production in rat renal papillary collecting tubule cells in culture. [Ca2+]i was measured using fura-2. When cells were exposed for one hour to the media supplemented with 0 mM Ca2+ (containing 1 mM EGTA), 1, 2, 3, 4, 6.4, or 8 mM Ca2+, basal [Ca2+]i ranged as below: 24.9 +/- 5.6, 90.7 +/- 7.4, 107.4 +/- 9.8, 146.1 +/- 13.7, 162.0 +/- 14.6, 241.5 +/- 32.8, and 234.9 +/- 29.6 nM, respectively. When medium Ca2+ was 1 mM, 1 x 10(-7) M AVP increased [Ca2+]i to 181.5 +/- 13.2 nM from 90.7 +/- 7.4 nM (P less than 0.01). AVP-induced increases in [Ca2+]i were obtained with the varying Ca2+ media described above, though the increases in [Ca2+]i were quantitatively variable. AVP-induced cellular cAMP production was examined during three minute incubation period in the presence of 5 x 10(-4) M 3-isobutyl-1-methylxanthine. Basal level of cellular cAMP was 87.6 +/- 7.9 fmol/micrograms protein.(ABSTRACT TRUNCATED AT 250 WORDS)