Activation of protein kinase C accelerates contraction kinetics of airway smooth muscle.
Contraction kinetics of isolated rat tracheal smooth muscle were studied by analysing the increase of force subsequent to force-inhibiting passive length changes lasting 1 s (100 Hz, sinus, 5% of muscle length). Compared with carbachol activation, phorboldibutyrate (PDBu)-induced stimulation of protein kinase C (PKC) demonstrated no significant difference in the extent of force development in the polarized preparation [mean peak force 9.16 +/- 0.37 mN (carbachol) vs. 9.12 +/- 0.37 mN (PDBu)]. However, the time constant calculated for the slow component of post-vibration force recovery was 6.40 +/- 0.29 s after addition of PDBu vs. 22.39 +/- 1.40 s during carbachol activation, indicating a significant phorbol ester-induced acceleration of the cross-bridge cycling rate. In the K-depolarized preparation, treatment with 26.4 microM indolactam (IL) to activate PKC produced muscle relaxation (9.94 +/- 0.16 mN measured 0-30 min after the onset of depolarization vs. 4.13 +/- 0.05 mN measured during 30-60 min of IL treatment). Again, even in the presence of high sarcoplasmic Ca2+ resulting from tonic depolarization, PKC activation was associated with a distinct diminution of the time constant (25.99 +/- 0.79 s during the first 30 min of depolarization vs. 10.32 +/- 0.21 s during 30-60 min of IL treatment). In contrast, addition of 0.035 microM verapamil, 1.5 microM isoproterenol, and 32 microM dibutyryl-cAMP to the bathing medium induced relaxation without affecting the rate of post-vibration force recovery. The results suggest that the calcium-dependent signal cascade (agonist receptor/inositol trisphosphate/ Ca(2+)-calmodulin/myosin light chain kinase) hardly affects the regulation of contraction kinetics in the tonically activated intact smooth muscle preparation. PKC stimulation, however, accelerates actin/myosin interaction kinetics, possibly by inhibition of phosphatase(s).
Peiper
U
U
Physiologisches Institut, Universitätskrankenhaus Eppendorf, Hamburg, Germany.
Knipp
S C
SC
Thies
B
B
Henke
R
R
D000818:Animals; D004594:Electrophysiology; D004789:Enzyme Activation; D066298:In Vitro Techniques; D007211:Indoles / Q000494:pharmacology; D007700:Kinetics; D007769:Lactams / Q000494:pharmacology; D009119:Muscle Contraction / Q000502:physiology*; D009126:Muscle Relaxation / Q000502:physiology; D009130:Muscle, Smooth / Q000187:drug effects / Q000201:enzymology / Q000502:physiology*; D015240:Phorbol 12,13-Dibutyrate / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology; D011493:Protein Kinase C / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D011976:Receptors, Muscarinic / Q000502:physiology; D014132:Trachea / Q000187:drug effects / Q000201:enzymology / Q000502:physiology*; D014700:Verapamil / Q000494:pharmacology; D014732:Vibration
D007211:Indoles; D007769:Lactams; D011976:Receptors, Muscarinic; D015240:Phorbol 12,13-Dibutyrate; C043969:indolactam V; D014700:Verapamil; D011493:Protein Kinase C; D011188:Potassium