Oscillations of intracellular calcium induced by vasopressin in individual fura-2-loaded mesangial cells. Frequency dependence on basal calcium concentration, agonist concentration, and temperature.
Intracellular free calcium concentration ([Ca2+]i) was measured in fura-2-loaded single rat mesangial cells by dual wavelength spectrofluorometry. Stimulation with arginine vasopressin (AVP) caused an initial sharp rise of [Ca2+]i followed by repetitive spikes. The frequency of the oscillations was dependent on the concentration of AVP. At 0.1, 1.0, 10.0, and 100.0 nM AVP, the frequencies of oscillations were 0.17 +/- 0.05 (n = 6), 0.32 +/- 0.05 (n = 6), 0.49 +/- 0.05 (n = 6), and 0.48 +/- 0.05 min-1 (n = 5), respectively. Reduction in extracellular [Ca2+] reduced the frequency of AVP-induced oscillations but did not abolish the oscillations. The frequency of calcium oscillations, upon stimulation with 1.0 nM AVP, was directly correlated with the basal [Ca2+]i prior to stimulation. Oscillation frequency increased with increasing temperature. An Arrhenius plot between 24 and 37 degrees C indicated a strong temperature dependency of the oscillations with a Q10 of 3.0. Protein kinase C stimulation by active phorbol esters inhibited AVP-induced calcium oscillations but not the initial [Ca2+] response to AVP. These observations are consistent with a model incorporating a feedback loop linking [Ca2+]i to the mechanism of [Ca2+]i increase. Ca(2+)-induced Ca2+ release may be involved, whereby inositol 1,4,5-trisphosphate (inositol 1,4,5-P3) formation releases Ca2+ from an inositol 1,4,5-P3-sensitive pool, with subsequent Ca2+ uptake and release from an inositol 1,4,5-P3-insensitive pool.
Hajjar
R J
RJ
Medical Services, Massachusetts General Hospital, Boston 02114.
Bonventre
J V
JV
D000818:Animals; D001127:Arginine Vasopressin / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism* / Q000494:pharmacology; D002478:Cells, Cultured; D015232:Dinoprostone / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation; D016257:Fura-2; D005920:Glomerular Mesangium / Q000187:drug effects / Q000378:metabolism*; D007700:Kinetics; D008856:Microscopy, Fluorescence; D011493:Protein Kinase C / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D013696:Temperature
D001127:Arginine Vasopressin; D011493:Protein Kinase C; D015232:Dinoprostone; D002118:Calcium; D016257:Fura-2