Length-dependence of lymphatic phasic contractile activity under isometric and isobaric conditions.
Length-dependence of lymphatic phasic contractile activity under isometric and isobaric conditions.
复制标题
等长和等压条件下淋巴阶段性收缩活动的长度依赖性。
DOI：
10.1080/10739680701436160
复制
发表时间：
2007
期刊：
影响因子：
--
通讯作者：
Davis,MichaelJ
中科院分区：
文献类型：
--
作者：
Zhang,Rongzhen;Gashev,AnatoliyA;Zawieja,DavidC;Lane,MeganM;Davis,MichaelJ
Objective:Experiments were designed to determine if the effect of preload on the spontaneous contractile activity of rat mesenteric lymphatics would be different under isometric and isobaric conditions.Methods:Isobaric protocols on cannulated, pressurized rat mesenteric lymphatics (∼ 120 μ m, ID) measured the effects of lumenal pressure on contraction amplitude, frequency, and rate of diameter change (dD/dt). Analogous protocols were conducted using a wire myograph to determine the effects of passive force (preload) on the characteristics of spontaneous, isometric force transients. Servo-control systems allowed responses to ramp or step increases in preload/pressure to be tested.Results:Under isobaric conditions, contraction amplitude was maximal at the lowest pressure tested (1 cm H2O), and progressively declined with pressure elevation to 10 cm H2O. Changes indD/dtfollowed a similar pattern. In contrast, contraction frequency progressively increased with pressure. Under isometric conditions, the amplitude of spontaneous force transients was maximal at preloads of 0.3–0.4 mN, withdF/dtfollowing a similar pattern; the average peak amplitude was ∼ 15% of the maximal active contractile force developed during agonist stimulation. The frequency of the transients increased with preload from 0.05 to 0.3 mN, and remained constant at higher preloads. The amplitude-frequency product, an estimate of lymphatic pumping ability, reached a maximum value at 0.4 mN in isometric vessels and at 6 cm H2O in isobaric vessels.Conclusions:Isometric and isobaric methods yielded qualitatively similar indices of spontaneous contractile activity. However, the ranges of amplitude and frequency changes were much greater under isobaric conditions (3- to 5-fold) than under isometric conditions (50–80%).
