Mechanisms of Acute Alcohol Intoxication-Induced Modulation of Cyclic Mobilization of [Ca\u3csup\u3e2+\u3c/sup\u3e] in Rat Mesenteric Lymphatic Vessels

Background: We have demonstrated that acute alcohol intoxication (AAI) increases the magnitude of Ca2+ transients in pumping lymphatic vessels. We tested the contribution of extracellular Ca2+ via L-type Ca2+ channels and intracellular Ca2+ release from the sarcoplasmic reticulum (SR) to the AAI-induced increase in Ca2+ transients. Methods and Results: AAI was produced by intragastric administration of 30% alcohol to conscious, unrestrained rats; isovolumic administration of water served as the control. Mesenteric lymphatic vessels were isolated, cannulated, and loaded with Fura-2 AM to measure changes in intracellular Ca2+. Measurements were made at intraluminal pressures of 2, 6, and 10 cm H2O. L-type Ca2+ channels were blocked with nifedipine; IP-3 receptors were inhibited with xestospongin C; and SR Ca2+ release and Ca2+ pool (Ca2+ free APSS) were achieved using caffeine. Nifedipine reduced lymphatic Ca2+ transient magnitude in both AAI and control groups at all pressures tested, but reduced lymphatic contraction frequency only in the control group. Xestospongin C did not significantly change any of the Ca2+ parameters in either group; however, fractional shortening increased in the controls at low transmural pressure. RyR (ryanodine receptor) activation with caffeine resulted in a single contraction with a greater Ca2+ transient in lymphatics from AAI than those from controls. SR Ca2+ pool was also greater in lymphatics isolated from AAI- than from control animals. Conclusions: These data suggest that 1) L-type Ca2+ channels contribute to the AAI-induced increase in lymphatic Ca2+ transient, 2) blockage of IP-3 receptors could increase calcium sensitivity, and 3) AAI increases Ca2+ storage in the SR in lymphatic vessels