Dissociation of Ca2+ entry and Ca2+ mobilization responses to angiotensin II in bovine adrenal chromaffin cells

• Published in: The Journal of biological chemistry Vol. 264; no. 31; pp. 18349 - 18355
• Main Authors: Stauderman, K A, Pruss, R M
• Format: Journal Article
• Language: English
• Published: Bethesda, MD Elsevier Inc 05-11-1989; American Society for Biochemistry and Molecular Biology
• Subjects: Adrenal Glands - drug effects; Adrenal Glands - metabolism; Angiotensin II - pharmacology; Animals; Biological and medical sciences; Calcium - metabolism; Calcium Radioisotopes; Cations, Divalent; Cattle; Cell physiology; Chlorides; Chromaffin System - drug effects; Chromaffin System - metabolism; Egtazic Acid - pharmacology; Extracellular Space - metabolism; Fundamental and applied biological sciences. Psychology; Hormonal regulation; Inositol 1,4,5-Trisphosphate - metabolism; Intracellular Fluid - metabolism; Ionomycin - pharmacology; Lanthanum - pharmacology; Manganese - metabolism; Manganese - pharmacology; Manganese Compounds; Molecular and cellular biology; Spectrometry, Fluorescence; Cell culture; Bovine; Radiolabelling; Adrenal glands; HPLC chromatography; Ion transport; Calcium Ions; Chromaffin cell; Fluorescence spectrometry; Protein hormone; Vertebrata; Mammalia; Plasma membrane; Hormonal regulation; Artiodactyla; Angiotensin II; Ungulata
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1016/S0021-9258(18)51470-8

In fura-2-loaded bovine adrenal chromaffin cells, 0.5 microM angiotensin II (AII) stimulated a 185 ± 19 nM increase of intracellular-free calcium [(Ca2+]i) approximately 3 s after addition. The time from the onset of the response until achieving 50% recovery (t ½) was 67 ± 10 s. Concomitantly, AII stimulated both the release of 45Ca2+ from prelabeled cells, and a 4-5-fold increase of [3H]inositol 1,4,5-trisphosphate ([3H]Ins(1,4,5)P3) levels. In the presence of 50 µM LaCl3, or when extracellular-free Ca2+ [(Ca2+]o) was less than 100 nM, AII still rapidly increased [Ca2+]i by 95-135 nM, but the t ½ for recovery was then only 23-27 s. In medium with 1 mM MnCl2 present, AII also stimulated a small amount of Mn2+ influx, as judged by quenching of the fura-2 signal. When [Ca2+]o was normal (1.1 mM) or low (less than 60 nM), 1-2 microM ionomycin caused [Ca2+]i to increase 204 ± 26 nM, while also releasing 45-55% of bound 45Ca2+. With low [Ca2+]o, ionomycin pretreatment abolished both the [Ca2+]i increase and 45Ca2+ release stimulated by AII. However, after ionomycin pretreatment in normal medium, AII produced a La3+-inhibitable increase of [Ca2+]i (103 ± 13 nM) with a t ½ of 89 ± 8 s, but no 45Ca2+ release. No pretreatment condition altered AII-induced formation of [3H]Ins(1,4,5)P3. We conclude that AII increased [Ca2+]i via rapid and transient Ca2+ mobilization from Ins(1,4,5)P3- and ionomycin-sensitive stores, accompanied (and/or followed) by Ca2+ entry through a La3+-inhibitable divalent cation pathway. Furthermore, the ability of AII to activate Ca2+ entry in the absence of Ca2+ mobilization (i.e. after ionomycin pretreatment) suggests a receptor-linked stimulus other than Ca2+ mobilization initiates Ca2+ entry.