A Ca2+-linked increase in coupled cAMP synthesis and hydrolysis is an early event in cholinergic and beta-adrenergic stimulation of parotid secretion.
AUTOR(ES)
Deeg, M A
RESUMO
The dynamics and compartmental characteristics of cAMP metabolism were examined by 18O labeling of cellular adenine nucleotide alpha phosphoryls in rat parotid gland stimulated to secrete with beta-adrenergic and cholinergic agents. The secretory response occurred in association with a rapidly increased rate of cAMP hydrolysis apparently coordinated with an equivalent increase in the rate of cAMP synthesis, since the cellular concentration of cAMP remained unchanged. The magnitude of this metabolic response was equivalent to the metabolism of 10-75 times the cellular content of cAMP within the first minute of stimulation. This increased metabolic rate occurred only during the early (1-3 min) period of stimulation, in what appeared to be an exclusive cellular compartment distinguished by a unique distribution of 18O among adenine nucleotide alpha phosphoryls. This 18O distribution contrasted with that produced by forskolin, which increased cellular cAMP concentration and elicited only a delayed response missing the early secretory component. The early acceleration of cAMP metabolism appeared linked to a stimulus-induced increase in intracellular Ca2+ concentration, since the Ca2+ ionophore ionomycin produced the same metabolic response in association with secretion. These observations suggest that cAMP metabolism is involved in stimulus-secretion coupling by a Ca2+-linked mechanism different from that in which cAMP plays the role of a second messenger.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=282298Documentos Relacionados
- cAMP compartmentation is responsible for a local activation of cardiac Ca2+ channels by beta-adrenergic agonists.
- Early posthypoglycemic insulin resistance in man is mainly an effect of beta-adrenergic stimulation.
- Stimulation of amyloid precursor protein synthesis by adrenergic receptors coupled to cAMP formation
- beta-Adrenergic receptor agonists increase phospholipid methylation, membrane fluidity, and beta-adrenergic receptor-adenylate cyclase coupling.
- beta-Adrenergic receptor regulation of N-linked protein glycosylation in rat parotid acinar cells.