cAMP- and diacylglycerol-mediated pathways elevate cytosolic free calcium concentration via dihydropyridine-sensitive, omega-conotoxin-insensitive calcium channels in normal rat anterior pituitary cells.
Naunyn Schmiedebergs Arch Pharmacol
; 339(1-2): 1-7, 1989.
Article
em En
| MEDLINE
| ID: mdl-2542803
ABSTRACT
The effect of 8-bromocyclic AMP (8-Br-cAMP) and phorbol 12-myristate 13-acetate (PMA), a protein kinase C activator, on cytosolic free calcium concentration ([Ca2+]i) in normal rat anterior pituitary cells was examined. [Ca2+]i was monitored directly by the fluorescent indicator fura-2. 8-Br-cAMP as well as PMA elevated [Ca2+]i in a concentration-dependent manner. Forskolin (10 mumol/l), which activates adenylate cyclase, and 1-oleoyl-2-acetyl-glycerol (10 mumol/l), another activator of protein kinase C, also increased [Ca2+]i. Both the 8-Br-cAMP (2 mmol/l)- and the PMA (100 nmol/l)-induced increase in [Ca2+]i was dependent on the presence of extracellular calcium and could be inhibited by the calcium channel blockers Mg2+ and nifedipine, but not by omega-conotoxin (100 nmol/l). The half-maximally inhibitory concentrations of Mg2+ and nifedipine were about 12 mmol/l and 160 nmol/l, respectively, for the [Ca2+]i response to 8-Br-cAMP (2 mmol/l), and were about 6 mmol/l and 400 nmol/l, respectively, for the PMA (100 nmol/l)-induced increase in [Ca2+]i. The sodium channel blocker tetrodotoxin (5 mumol/l) or PMA (100 nmol/l) on [Ca2+]i. After pretreatment for 3 min with PMA (100 nmol/l), the subsequent K+ (100 mmol/l)- or arachidonic acid (3 mumol/l)-induced increase in [Ca2+]i was decreased by about 50%. By contrast, pretreatment (3 min) with 8-Br-cAMP (2-10 mmol/l) markedly enhanced the subsequent [Ca2+]i response to K+ (100 mmol/l), and left the effect of arachidonic acid (3 mumol/l) on [Ca2+]i unimpaired.(ABSTRACT TRUNCATED AT 250 WORDS)
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Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Adeno-Hipófise
/
Canais de Cálcio
/
Cálcio
/
AMP Cíclico
/
Citosol
/
Diglicerídeos
/
Glicerídeos
Tipo de estudo:
Diagnostic_studies
Limite:
Animals
Idioma:
En
Revista:
Naunyn Schmiedebergs Arch Pharmacol
Ano de publicação:
1989
Tipo de documento:
Article