Ramagopal M V, Mustafa S J
Department of Pharmacology, School of Medicine, East Carolina University, Greenville, North Carolina 27858-4354.
Am J Physiol. 1988 Dec;255(6 Pt 2):H1492-8. doi: 10.1152/ajpheart.1988.255.6.H1492.
In the present study, we have investigated the changes in calcium influx during the relaxing responses to adenosine and its analogues. Calcium-45 influx was measured in bovine coronary artery rings in the presence of prostaglandin F2 alpha (10(-5) M) and KCl (50 and 100 mM). Prostaglandin F2 alpha and KCl caused increases in calcium influx. Prostaglandin F2 alpha produced a further contraction when added to rings maximally contracted with KCl (100 mM or higher), suggesting two different mechanisms for prostaglandin F2 alpha- and KCl-induced contractions. Similarly, a greater calcium influx was observed when prostaglandin F2 alpha was mixed with KCl (50 or 100 mM). At all the concentrations tested, adenosine and its analogues [5'-(N-ethyl-carboxamidoadenosine, NECA; N6-(L-2-phenylisopropyl)adenosine, L-PIA] significantly inhibited prostaglandin F2 alpha-induced increases in calcium influx. However, only higher concentrations of adenosine, NECA, and L-PIA inhibited 100 mM KCl-induced calcium influx. Previous treatment with 8-phenyltheophylline blocked the inhibitory actions of adenosine, NECA, and L-PIA on calcium influx. The inhibition of calcium influx by adenosine, NECA, and L-PIA correlated well with their relaxing ability in the presence of prostaglandin F2 alpha. The data suggest that prostaglandin F2 alpha-induced calcium influx was more sensitive to the action of adenosine and its analogues than the calcium influx induced by high K+ depolarization.
在本研究中，我们研究了腺苷及其类似物引起舒张反应期间钙内流的变化。在存在前列腺素F2α（10⁻⁵ M）和氯化钾（50 mM和100 mM）的情况下，测定牛冠状动脉环中的⁴⁵钙内流。前列腺素F2α和氯化钾导致钙内流增加。当将前列腺素F2α添加到用氯化钾（100 mM或更高）最大收缩的环中时，会产生进一步的收缩，这表明前列腺素F2α和氯化钾引起收缩的机制不同。同样，当前列腺素F2α与氯化钾（50 mM或100 mM）混合时，观察到更大的钙内流。在所有测试浓度下，腺苷及其类似物[5'-(N-乙基-羧酰胺基腺苷，NECA；N⁶-(L-2-苯异丙基)腺苷，L-PIA]均显著抑制前列腺素F2α诱导的钙内流增加。然而，只有较高浓度的腺苷、NECA和L-PIA抑制100 mM氯化钾诱导的钙内流。预先用8-苯基茶碱处理可阻断腺苷、NECA和L-PIA对钙内流的抑制作用。腺苷、NECA和L-PIA对钙内流的抑制作用与其在前列腺素F2α存在下的舒张能力密切相关。数据表明，前列腺素F2α诱导的钙内流比高钾去极化诱导的钙内流对腺苷及其类似物的作用更敏感。
