Activation of tracheal smooth muscle contraction: synergism between Ca2+ and activators of protein kinase C.

Abstract

The effects of divalent ionophores (A23187 and ionomycin), Ca2+ channel agonist (BAY K 8644), and protein kinase C (C-kinase) activators [phorbol 12-myristate 13-acetate (PMA), mezerein] on bovine tracheal smooth muscle contraction were investigated. A23187 (5 gLM) and ionomycin (0.5 jLM) produced a prompt but transient contraction. Ckinase activators either produced no effect-e.g., PMA at 200 nM-or produced a rise in tension that was slow in onset but then gradually increased-e.g., mezerein at 400 nM. In contrast, ionophores and C-kinase activators, in combination, acted synergistically to produce a prompt and sustained contractile response that is reminiscent of that observed in response to carbachol, a cholinergic agonist. In addition, BAY K 8644 (20 nM), which has a minimal effect on tension by itself, could significantly enhance contraction induced by C-kinase activators. The contraction induced by all of these agents was quickly reversed either by removal of extracellular Ca2" or upon addition of forskolin, an activator of adenylate cyclase. A similar reversal of carbachol-induced contraction by forskolin was observed with carbachol-induced contraction. These rindings strongly suggest that C-kinase plays an important role in mediating tracheal smooth muscle contraction.

Inhibition of histamine‐stimulated inositol phospholipid hydrolysis by agents which increase cyclic AMP levels in bovine tracheal smooth muscle

“…The time course of this effect on inositol phosphate accumulation is similar to the rapid relaxation produced by fi-agonists in bovine and canine tracheal smooth muscle strips which have been previously contracted by smooth muscle spasmogens (Fujiwara et al, 1988;Takuwa et al 1988). This raises the possibility that inhibition of histamine-stimulated inositol phospholipid hydrolysis by f2-agonists may contribute to the relaxation of pre-contracted (with histamine) airway smooth muscle by preventing the formation of either the calcium-mobilising inositol-1,4,5-trisphosphate or 1,2-diacylgycerol, which appears to be responsible for the maintenance of the contractile state via the activation of protein kinase C (Park & Rasmussen, 1985;Dale & Obianime, 1985;Takuwa et al, 1987).…”

“…Histamine H1-receptor stimulation in tracheal smooth muscle produces a contractile response which appears to be initiated via the mobilization of calcium from intracellular stores (Takuwa et al, 1987;Kotlikoff et al, 1987) and maintained by the activation of protein kinase C (Park & Rasmussen, 1985;Dale & Obianime, 1985;Takuwa et al, 1987). Studies in canine tracheal smooth muscle (Hashimoto et al, 1985) and other tissues (Berridge, 1987) have shown that inositol-1,4,5-trisphosphate, which is produced following agonist-stimulated inositol phospholipid hydrolysis, can mobilise calcium ions from intracellular stores whilst 1,2-dia-1 Author for correspondence.…”

Protein kinase C translocation in intact vascular smooth muscle strips

“…Support for this assumption comes from contraction studied with phorbol esters, activators of PKC [11]. Exposure of smooth muscle strips to phorbol ester leads to a slowly developing contraction which lasts for several hours [12][13][14]. It has also been shown that phorbol esters induce a sustained contraction in chemically skinned vascular smooth muscle when the Ca2+ concentration is maintained at 100 nM [15].…”

“…The phosphorylation of these proteins appears to occur as a direct or indirect consequence of the activation of PKC [17]. The temporal change in the pattern of phosphoproteins and the distinct effects ofphorbol esters on smooth muscle contraction [12][13][14] have led to the proposal that the initial and sustained phases of smooth muscle contraction are mediated by different cellular and molecular events [17]. In this model, the initial phase is characterized by an increase in the cytosolic Ca2+ concentration, the activation of the calmodulin-dependent myosin-light-chain kinase, the phosphorylation of the myosin light chains, an interaction of actin and myosin, and hence contraction.…”

Probable involvement of epsilon-isoform of protein kinase C in rat bronchial smooth muscle contraction induced by acetylcholine

“…Although the role of each PKC isoform in agonist-induced bronchial smooth muscle contraction is unclear, PKC can phosphorylate a number of key contractile proteins in airway smooth muscle. PKC activation appears to be more involved in the sustained rather than the initial phases of airway smooth muscle contraction (Park and Rasmussen, 1985).…”