Calcium uptake-dependent and -independent mechanisms of inositol trisphosphate formation in adrenal chromaffin cells: comparative studies with high K+, carbamylcholine and angiotensin II.
When [3H]inositol prelabelled cultured bovine adrenal chromaffin cells were stimulated with 56 mM KCl (high K+), 300 microM carbamylcholine (CCh) or 10 microM angiotensin II (Ang II), a rapid accumulation of [3H]IP3 was observed. At the same time, high K+ or CCh induced rapid increases in 45Ca2+ uptake, but Ang II did not induce a significant 45Ca2+ uptake. The concentration-response curve for KCl-induced [3H]IP3 accumulation coincided well with that for KCl-induced 45Ca2+ uptake into the cells. Nifedipine, a Ca2+ channel antagonist, inhibited the high K(+)-induced [3H]IP3 accumulation and 45Ca2+ uptake with a similar potency. Nifedipine at a similar concentration range also inhibited CCh-induced 45Ca2+ uptake. Although nifedipine inhibited CCh-induced [3H]IP3 accumulation, the potency was approximately 300-fold less than that for the inhibition of 45Ca2+ uptake. Nifedipine failed to affect the Ang II-induced [3H]IP3 accumulation. BAY K 8644 (2 microM), a Ca2+ channel activator, plus partially depolarizing concentration of KCl (14 mM), induced 45Ca2+ uptake and [3H]IP3 accumulation. Ionomycin (1 microM and 10 microM), a Ca2+ ionophore, also induced 45Ca2+ uptake and [3H]IP3 accumulation in a concentration-dependent manner. Pretreatment of the cells with protein kinase C activator, 100 nM 12-O-tetradecanoyl phorbol-13-acetate, for 10 min, partially inhibited CCh and Ang II-induced [3H]IP3 accumulation, but failed to inhibit the high K(+)-induced accumulation. Furthermore, the effects of high K+ and Ang II on the IP3 accumulation was additive. Ang II and CCh induced a rapid and transient increase in inositol 1,4,5-trisphosphate (1,4,5-IP3) accumulation (5 s) followed by a slower accumulation of inositol 1,3,4-trisphosphate (1,3,4-IP3). High K+ evoked an increase in 1,3,4-IP3 accumulation but obvious accumulation of 1,4,5-IP3 could not be detected. In Ca2(+)-depleted medium, high K(+)-induced [3H]IP3 accumulation was completely abolished, whereas [3H]IP3 accumulation induced by CCh and Ang II was partially inhibited. These results demonstrate the existence of the Ca2+ uptake-triggered mechanism of IP3 accumulation represented by high K+, and also the Ca2+ uptake-independent mechanism of IP3 accumulation represented by Ang II in cultured bovine adrenal chromaffin cells. Mechanism of CCh-induced IP3 accumulation has an intermediate property between those of high K+ and Ang II.
Sasakawa
N
N
Department of Pharmacology, School of Medicine, Keio University, Tokyo, Japan.
Nakaki
T
T
Yamamoto
S
S
Kato
R
R
D000313:Adrenal Medulla / Q000166:cytology / Q000378:metabolism*; D000804:Angiotensin II / Q000502:physiology; D000818:Animals; D002118:Calcium / Q000502:physiology*; D002120:Calcium Channel Agonists / Q000494:pharmacology; D002132:Calcium Radioisotopes; D002217:Carbachol / Q000494:pharmacology; D002417:Cattle; D002851:Chromatography, High Pressure Liquid; D066298:In Vitro Techniques; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism*; D007295:Inositol Phosphates / Q000378:metabolism*; D009543:Nifedipine / Q000494:pharmacology; D011188:Potassium / Q000502:physiology; D011189:Potassium Chloride / Q000494:pharmacology; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D013997:Time Factors; D014316:Tritium
D002120:Calcium Channel Agonists; D002132:Calcium Radioisotopes; D007295:Inositol Phosphates; D014316:Tritium; D000804:Angiotensin II; D011189:Potassium Chloride; D015544:Inositol 1,4,5-Trisphosphate; D002217:Carbachol; C058097:inositol 1,3,4-trisphosphate; D009543:Nifedipine; D013755:Tetradecanoylphorbol Acetate; D011188:Potassium; D002118:Calcium