Beta-agonist-induced constitutive beta(2)-adrenergic receptor activity in bovine tracheal smooth muscle.

According to the two state receptor model, the beta(2)-adrenergic receptor (beta(2)-AR) isomerizes between an inactive state and a constitutively active state, which couples to the stimulatory G-protein in the absence of agonist. In bovine tracheal smooth muscle (BTSM), we investigated the effect of short and long term beta(2)-AR activation by fenoterol on constitutive receptor activity. Preincubation of the BTSM strips for 5 min, 30 min and 18 h with 10 microM fenoterol, followed by extensive washout (3 h, 37 degrees C), caused a rapid and time-dependent inhibition of KCl-induced contraction, reaching 68+/-10, 51+/-6 and 46+/-4% of control, respectively, at 40 mM KCl (P:<0.

Modulation of agonist-induced phosphoinositide metabolism, Ca2+ signalling and contraction of airway smooth muscle by cyclic AMP-dependent mechanisms.

1. The effects of increased cellular cyclic AMP levels induced by isoprenaline, forskolin and 8-bromoadenosine 3':5'-cyclic monophosphate (8-Br-cyclic AMP) on phosphoinositide metabolism and changes in intracellular Ca2+ elicited by methacholine and histamine were examined in bovine isolated tracheal smooth muscle (BTSM) cells. 2.

Feedforward control of agonist-induced Ca2+ signalling by protein kinase C in airway smooth muscle cells.

In isolated bovine tracheal smooth muscle cells, the potent and specific protein kinase C inhibitor GF 109203X caused an inhibition of methacholine-and histamine-induced Ca2+ mobilization and influx, indicating for the first time that protein kinase C activation induced by contractile agonists exerts a positive feedforward control of Ca2+ signalling by these agonists.

Regulation of histamine- and UTP-induced increases in Ins(1,4,5)P3, Ins (1,3,4,5)P4 and Ca2+ by cyclic AMP in DDT1 MF-2 cells.

1. Stimulation of P2U-purinoceptors with UTP or histamine H1-receptors with histamine gave rise to the formation of inositol 1,4,5-trisphosphate (Ins(1,4,5)P3) and inositol 1,3,4,5-tetrakisphosphate (Ins(1,3,4,5)P4) in DDT1 MF-2 smooth muscle cells. 2.

Calcium release from separate receptor-specific intracellular stores induced by histamine and ATP in a hamster cell line.

1. The specificity of intracellular Ca2+ stores to Ca(2+)-mobilizing agonists was studied in DDT1 MF-2 vas deferens cells of the Syrian hamster. 2.