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KMID : 0378019910340080029
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New Medical Journal
1991 Volume.34 No. 8 p.29 ~ p.35
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Effects of Various Nucleotides on the Contraction of Rat Tracheal Smooth Muscle
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Abstract
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While ATP is a potent vasodilator in many vascular beds, vasoconstriction occurs in 0ther vasculatures. Recently the existence of purinergic nervous system and purinoceptors´which use the ATP and adenosine as a neurotransmitter in variety of organs has been reported. However, the characteristics of the purinoceptor are still not well known. The present study was designed to investigate i) the action of various nucleotides on the contraction of tracheal smooth muscle ii) the mechanism of the action of nucleotides on contraction and iii) the characteristics of purinoceptors on the tracheal smooth muscle.
Sprague-Dawley rat was anesthetized with Na-thiopental (40mg /Kg i.p. ). Trachea was removed and C-shaped ring of cartilage was sectioned in the middle. One end of the ring was tied to the bottom of incubation bath and the other was connected to a force transducer (Myograph, F-60, Narco). After equilibrium of 30-40 min, 100?M of a various nucleoside and mucleotides--adenosine, AMP, ADP, ATP, ATPP, ITP, GTP, and CTP--were added into the incubation medium. The contraction of tracheal smooth muscle by addition of various nucleotides was measured by force transducer and recorded on a Physiograph (MK-III, Narco). Effects of verapamil, a Ca++-channel blocker, methylene blue, reactive blue and Evans blue were also observed.
The main results of the experiments were
1) The adenine derivatives including adenosine, AMP, ADP, ATR. and ATPP increased the contractile force. of tracheal smooth muscle. The adenine compounds in order of activitiy were ATPP > ATP > ADP > AMP > adenosine.
2) Contractile responses of -tracheal smooth muscle were also demonstrated with other nucleotides such as ITP, GTP and CTP.
3) The increments of ATP-induced contractile response were attenuated by verapamil, a Ca++-channel blocker.
4) Methylene blue, reactive blue and Evans blue augmented the contractile response induced by ATP. In conclusion, rat tracheal smooth muscle also has P2-purinoceptors which use the various nucleotides as agonist. The nucleotide-induced increments of contractile force may; be mediated by Ca++`--influx through, the plasma membrane: The purine structure and the number of phosphate combined with nucleoside may . have an important role which affects the smoth muscle contraction of trachea.
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