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KMID : 0371919880010010045
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Journal of Wonju College of Medicine
1988 Volume.1 No. 1 p.45 ~ p.51
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Effects of Vriors Nucleotides of Portal vein Presure in the Isolated Rat Liver
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Abstract
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Nucleotides participate in nearly all biochemical process in the cell. In addition exogenous ATP(adenosine triphosphate) and related adenylates affect vascular resistance. While ATP and adenosine are potent vasodilators in many vascular beds, vasoconstriction also occurs in other vascular bed. In recent, the existence of a purinergic nervous system inn the various smooth muscle including blood vessel has been recognized. It utilizes adenosine or ATP as neurotransmitters or neuromodulators. Two types of purinergic receptors in the smooth muscle - P₁-receptors are most sensitive to adenosine and P₂-receptors are sensitive to ATP - has been reported. However, the characteristics of the purinergic receptors in the vascular bed is still not well known.
The present study was designed to investigate the action of various nucleotides on portal vein pressure and flow in the isolated perfused rat liver preparation. ITP, GTP, CTP, ATP, ADP, AMP and adenosine were employed. The rat of the Sprague Dawley(200~250gm) was anesthetized with pentobarbital sodium (30 ㎎/㎏) via the peritoneal cavity. the abdomen was opened through a mid-line incision and liver with portal vein was exposed. After ligating the abdominal vena cava above the renal vein, a PE-260 polyethylene tube was inserted into the portal vein and tied. The thorax was opened and another polyethylene tube was inserted and secured in the thoracic vena cava via penetration of the right atrium. The liver was rapidly excised, transferred onto a liver platform. The liver perfusions with Krebs-Ringer bicarbonate solution were carried in two ways: i) Perfusion through the portal vein with a constant prssure (25 Cm H₂O), ii) Perfusion through the portal vein with constant flow (50 ㎖/min) using a peristaltic pump.
The key findings were:
1. ATP decreased perfusion flow in proportion to its concentration.
2. Adenine derivatives increased perfusion pressure under constant flow in following order: ATP>ADP>AMP=Adenosine.
3. ITP, GTP and CTP also increased the perfusion pressure. The effect of ATP was most potent of the nucleotides.
In conclusion, the various nucleotides increase vascular resistance in the isolated rat liver. Structures of the nucleotides-nitrogenous base and phosphate number attached to the nucleoside may have an important role which affects smooth muscle contraction of the portal vein.
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