Prostaglandin F_2α가 가토 대동맥 평활근 수축성에 미치는 영향

The Effects of Prostaglandin F_2α on the Contractility of Vascular Smooth Muscle in the Aortic Strip of Rabbits

The effects of prostaglandin (PGF_2α) on the contractility of vascular smooth muscle were investigated in the helical strip of the rabbit aorta. The aortic strip was immersed in the phosphate-buffered Tyrode s solution which was equilibrated with 100% O_{2} at 35℃ and its isometric tension was measured. The contraction was induced by (PGF_2α), norepinephrine (NE), or potassium (40 mM) in the nomal Tyrode s solution (1 mM, Ca²⁺) or Ca²⁺-free Tyrode s solution. Effects of verapamil and phentolamine on the contraction were also observed. The aortic strip began to contract at the concentration of 5 μg% and reached the maximal contraction at the concentration of 150 μg% (PGF_2α). The maximal contraction was corresponded respectively to 52.2±3.0% and 81.5±3.5% of maximal contraction by NE (1 X 10^-5M) and 40 mM K⁺. And the maximal contractions by (PGF_2α) or NE were induced at the concentration of about 1 mM Ca²⁺. (PGF_2α) induced the contraction of aortic strip even after induction of contraction by 40 mM K⁺ and the contraction by (PGF_2α) was not blocked by the α-receptor blocker, phentolamine. And the contraction by the (PGF_2α) was inhibited partially by a verapamil at the concentration of 1 X 10^-5M and the contraction began to increase at the concentration of 1 X 10^-4M verapamil. Whereas the contraction by NE was completely blocked by verapamil. Though both the (PGF_2α) and NE induced the contraction in the Ca²⁺-free Tyrode s solution, the peak tension was not maintained. But the rate of tension decline was lower in the contraction by (PGF_2α) than in that by NE. The verapamil did not inhibit the contraction by (PGF_2α) in the Ca²⁺-free Tyrode s solution and increased the contraction at the concentration of above 1 X 10^-4M. The NE-induced contraction in the Ca²⁺-free Tyrode s solution was inhibited completely by a verapamil. From the above results it is suggested that the contraction induced by (PGF_2α) results from the promotion of the both Ca²⁺ influx and the intracellular Ca²⁺ release by different way from NE.