Atherogenic lipoproteins inhibit catecholamine secretion in cultured bovine adrenal medullary cells.
The effects of lipoproteins on ion channel-mediated catecholamine secretion were investigated in cultured bovine adrenal medullary cells. Low density lipoprotein (LDL: 20-80 mg/dl) and lipoprotein(a) [Lp(a); 10-80 mg/dl] inhibited catecholamine secretion induced by carbachol, an activator of nicotinic acetylcholine receptor-ion channels. LDL and Lp(a) suppressed carbachol-induced 22Na+ influx as well as 45Ca2+ influx in a concentration-dependent manner similar to that of catecholamine secretion. The inhibition of catecholamine secretion by Lp(a) was not overcome by increasing the concentration of carbachol. On the other hand, high density lipoprotein (HDL; < 150 mg/dl) had no effect on 22Na+ influx, 45Ca2+ influx, and catecholamine secretion. Like LDL and Lp(a), a synthetic peptide homologous to human plasma apolipoprotein B (apoB), apoB fragment(3358-3372)-amide (3-60 microM), attenuated 22Na+ influx, 45Ca2+ influx, and catecholamine secretion caused by carbachol. The apoB fragment also suppressed 22Na+ influx induced by veratridine (an activator of voltage-dependent Na+ channels) and 45Ca2+ influx induced by 56 mM K+ (an indirect activator of voltage-dependent Ca2+ channels). These findings suggest that atherogenic lipoproteins such as LDL and Lp(a) suppress catecholamine secretion by interfering with Na+ influx through nicotinic acetylcholine receptor-ion channels, in which apoB, a structural component common to both LDL and Lp(a), plays an important role. The inhibition by atherogenic lipoproteins of catecholamine secretion may influence the progression of atherosclerosis induced by these lipoproteins.
Second Department of Internal Medicine, University of Occupational and Environmental Health, School of Medicine, Kitakyushu, Fukuoka, Japan.
K
K
Kajiwara
N
N
Yanagihara
M
M
Tsutsui
A
A
Yashiro
H
H
Tasaki
Y
Y
Nakashima
F
F
Izumi
D000313:Adrenal Medulla / Q000187:drug effects* / Q000378:metabolism; D000818:Animals; D001055:Apolipoproteins B / Q000494:pharmacology; D002217:Carbachol / Q000494:pharmacology; D002395:Catecholamines / Q000378:metabolism*; D002417:Cattle; D002478:Cells, Cultured; D018679:Cholinergic Agonists / Q000494:pharmacology; D004347:Drug Interactions; D004591:Electrophoresis, Polyacrylamide Gel; D007473:Ion Channels / Q000187:drug effects / Q000378:metabolism; D017270:Lipoprotein(a) / Q000302:isolation & purification / Q000494:pharmacology; D008074:Lipoproteins / Q000302:isolation & purification / Q000494:pharmacology*; D008075:Lipoproteins, HDL / Q000302:isolation & purification / Q000494:pharmacology
D001055:Apolipoproteins B; D002395:Catecholamines; D018679:Cholinergic Agonists; D007473:Ion Channels; D017270:Lipoprotein(a); D008074:Lipoproteins; D008075:Lipoproteins, HDL; D002217:Carbachol