ABSTRACT
We have shown that myosin light chain kinase (MLCK) was required for the off-contraction in response to the electrical field stimulation (EFS) of feline esophageal smooth muscle. In this study, we investigated whether protein kinase C (PKC) may require the on-contraction in response to EFS using feline esophageal smooth muscle. The contractions were recorded using an isometric force transducer. On-contraction occurred in the presence of NG-nitro-L-arginine methyl ester (L-NAME), suggesting that nitric oxide acts as an inhibitory mediator in smooth muscle. The excitatory composition of both contractions was cholinergic dependent which was blocked by tetrodotoxin or atropine. The on-contraction was abolished in Ca2+-free buffer but reappeared in normal Ca2+-containing buffer indicating that the contraction was Ca2+ dependent. 4-aminopyridine (4-AP), voltage-dependent K+ channel blocker, significantly enhanced on-contraction. Aluminum fluoride (a G-protein activator) increased on-contraction. Pertussis toxin (a Gi inactivator) and C3 exoenzyme (a rhoA inactivator) significantly decreased on-contraction suggesting that Gi or rhoA protein may be related with Ca2+ and K+ channel. ML-9, a MLCK inhibitor, significantly inhibited on-contraction, and chelerythrine (PKC inhibitor) affected on the contraction. These results suggest that endogenous cholinergic contractions activated directly by low-frequency EFS may be mediated by Ca2+, and G proteins, such as Gi and rhoA, which resulted in the activation of MLCK, and PKC to produce the contraction in feline distal esophageal smooth muscle.
Subject(s)
4-Aminopyridine , Aluminum , Aluminum Compounds , Atropine , Azepines , Benzophenanthridines , Contracts , Esophagus , Fluorides , GTP-Binding Proteins , Muscle, Smooth , Myosin-Light-Chain Kinase , NG-Nitroarginine Methyl Ester , Nitric Oxide , Pertussis Toxin , Protein Kinase C , rhoA GTP-Binding Protein , Tetrodotoxin , TransducersABSTRACT
The introduction of the strong clover-leafed nail combined with the principle of reaming out the medullary canal and the development of image intensifiers has been extended the indications of the in tramedullary nailing. In this report, an attempt was made to introduce the method and to verify the indications and advantage of retrograde intramedullary nailing of humeral shaft fractures, as compared with the conventionally accepted methods.