Positive correlation between cytosolic free calcium and surfactant secretion in cultured rat alveolar type II cells

• Published in: Biochimica et biophysica acta Vol. 960; no. 1; pp. 43 - 53
• Main Authors: Pian, Mark S., Dobbs, Leland G., Düzgünes, Nejat
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 02.05.1988; Elsevier; North-Holland
• Subjects: Aminoquinolines - metabolism; Animals; Benzofurans - metabolism; Biological and medical sciences; Calcium - metabolism; Cell physiology; Cells, Cultured; Cytosol - drug effects; Cytosol - metabolism; Cytosolic calcium; Ethers - pharmacology; Fundamental and applied biological sciences. Psychology; Fura-2; Fura-2 - analogs & derivatives; Ionomycin; Male; Molecular and cellular biology; Phosphatidylcholines - metabolism; Pulmonary Alveoli - drug effects; Pulmonary Alveoli - metabolism; Pulmonary Surfactants - metabolism; Qu 2; Rat; Rats; Rats, Inbred Strains; Secretion. Exocytosis; Spectrometry, Fluorescence; Surfactant secretion; Terbutaline - pharmacology; Tetradecanoylphorbol Acetate - pharmacology; Type II cell; Qu 2; Tris, 2-amino-2-hydroxymethylpropane-1,3-diol; Cytosolic calcium; Surfactant secretion; Rat; TPA, tetradecanoylphorbol acetate; DMEM, Dulbecco's modified Eagle's medium; [Ca 2+] i, cytosolic free calcium concentration; AM, acetoxymethyl ester; Fura-2; Hepes, 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid; Type II cell; Alveolar type II cell; Cell culture; Calcium; Secretion; Lung; Rodentia; Fluorescence; Activation; Assay; Vertebrata; Regulation(control); Mammalia; Pulmonary surfactant; Second messenger; Intracellular
• ISSN: 0005-2760; 0006-3002; 1879-145X; 1878-2434
• DOI: 10.1016/0005-2760(88)90007-0

To determine whether increases in the cytosolic free Ca 2+ concentration ((Ca 2+] i) accompany agoniststimulated surfactant secretion by cultured alveolar type II cells, we measured the [Ca 2+] i of quin2-loaded cells isolated from adult rats before and after cells were stimulated with ionomycin, terbutaline or tetradecanoylphorbol acetate (TPA). To determine whether increases in [Ca 2+] i are necessary for stimulated surfactant secretion to occur, we measured secretion in cells after [Ca 2+] i had been reduced by loading cells with quinl in medium containing low [Ca 2+]. Ionomycin increased [Ca 2+] i and stimulated surfactant secretion in a dose-dependent manner. Reductions in [Ca 2+] i correlated with reductions in secretion stimulated by ionomycin, terbutaline or TPA. Ionomycin-stimulated secretion was most sensitive to reductions in [Ca 2+] i; terbutaline-stimulated secretion was more sensitive than TPA-stimulated secretion. When [Ca2+] i was less than 65 nM, all stimulated secretion was blocked. Restoration of [Ca 2+] i to greater than 100 nM restored ionomycin-stimulated secretion. We conclude that ionomycin increases [Ca 2+] i and stimulates surfactant secretion in cultured alveolar type II cells, and that increased [Ca 2+] i appears to be necessary for ionomycin-stimulated secretion to occur. Terbutaline-stimulated surfactant secretion seems to be more easily inhibited by a reduction in [Ca 2+] i than does TPA-stimulated secretion.