Lymphatic Htpo-Reactivity In Hemorrhagic Shock Rats And Its Mechanism Of Calcium Sensitivity

During the episodes of hemorrhagic shock, microcirculatorydisturbances, inflammatory cascade effects, fluid resuscitation inducingreperfusion injury as well as vascular hypo-reactivity and no-reflowphenomenon have been considered the main contributors of the refractoryhypotension, multiple organ dysfunction syndromes (MODS) and evenmultiple organ failure, which remains the major common cause of highmortality. Therefore, the pathogenesis and therapy of hemorrhagic shockis still a hotspot and difficulty in studies of critical care medicine. Lymphcirculation is an important component of the circulatory system and playsa vital role in the progress of severe shock. It has been documented thatthe contractile function of lymphatic reduced significantly accompaniedwith blood circulation disorders in the development of severe shock, andit exacerbated the progress of irreversible shock as well. In the procedureof resuscitation, the recovery of lymph circulation precedes blood systemand can promote the restoration of blood circulation and, moreover,contribute to the outcome of severe shock. For this reason, the role oflymphatic hypo-reactivity in the pathogenesis of shock is worth our muchmore attention and its pathogenesis still remains to be further addressed.Lymphatic reactivity, which refers to contractile function of lymphatic tovasoconstrictors, is based on lymphatic smooth muscle cells (LMSC).LSMC possess a similar structure and function with vascular smoothmuscle cells. Therefore, whether lymphatic hypo-reactivity exists in theprocess of lymphatic contractile dysfunction of the shock sufferers andwhether lymphatic hypo-reactivity involves calcium desensitization which often occurs in the blood vessels subjected to severe shock remain to befully elucidated. All these problems are urgently needed to be solved.Therefore, in this study, the aim is to observe the changes oflymphatic pressor and the ML contractility response to norepinephrine(NE) during the process of hemorrhagic shock, and to observe thereactivity changes of lymphatic to NE from hemorrhagic shock rats invitro. explore whether there is a decreased response of lymphatic duringthe process of hemorrhagic shock, and the relationship of lymphatic andvascular differences between these two vessels; and to observe the calciumsensitivity changes of lymphatic from hemorrhagic shock rats in vitro,explore the mechanism of calcium sensitivity of lymphatic hypo-reactivityin hemorrhagic shock rats.Sixteen male Wistar rats were randomly divided into sham group(surgical procedure only) and hemorrhagic shock (40 mmHg for 180minutes) group. Hemorrhagic shock was induced by taking blood from thefemoral artery until a mean arterial blood pressure of 40 mmHg wasreached. This mean arterial pressure maintained for 180 min. Thelymphatic internal pressure (LP) and mean arterial pressure (MAP) weremonitored through a catheter in thoracic duct and femoral arteryrespectively. At different time points in the process of whole experiment,LP and MAP were recorded after administration of norepinephrine (NE),an indicator of lymphatic and vascular response. The results showed thatthere were no significant differences in response of LP to NE at the end ofhemorrhage between shock group and sham group (P<0.05). Comparedwith sham group, there were no significant differences in pressor responseof LP at pre-shock and 0h (P<0.05). The response of lymphatic began tofall at 0.5h of shock and still maintained a low reactivity at 3h after shock(P<0.05, P<0.01). However, compared with sham group, the response ofMAP to NE displayed a biphasic change. The response of MAP to NE increased at 0h of shock and began to fall at 1h. Moreover, thehypo-reactivity of LP and MAP to NE were significant correlated.Sixteen male Wistar rats were randomly divided into Sham andhemorrhagic shock group. For the mesentery preparation, the mesenterywas exposed via an abdominal incision. The ileocecal portion ofmesentery was withdrawn and loosely draped over an observation windowon a heated animal stage by gentle manipulation. The spontaneouscontraction frequency (F), maximal contraction diameter (a), maximaldiastolic diameter (b) and static diameter (c) were computed throughmicrocirculation video surveillance systems continuously and the changesof frequency, Index I, IndexⅡ, LD-Index (values were shown by△F,△Index I,△IndexⅡ,△LD-Index) after administration of NE (5μg?kg-1)at different time points of the process of experiments. The results showedthat the changes of ML contractile response to NE had no obviouslydifferences in Sham group during the process of experiment. The values of△F,△Index I,△IndexⅡ,△LD-Index had no significant differencesin HS group at pre-shock, shock 0h and 0.5h compared with the Shamgroup. Moreover, no group differences were observed (P<0.05, P<0.01).In HS group, the values of△F,△IndexⅡ,△LD-Index at shock 1h, thevalues of△F,△Index I,△IndexⅡ,△LD-Index at shock 1.5h and 2hwere significantly lower than those of Sham group, and the values of△F,△Index I,△IndexⅡ,△LD-Index at the 3h significantly decreasedcompared with the pre-shock (P<0.05, P<0.01).The other Male Wistar rats were randomly divided into Sham andhemorrhagic shock group (were divided into 1h and 2h two sub-groups).In vitro lymphatic separation technology, was taken thoracic duct (TD)from hemorrhagic shock rats and preparation of lymphatic rings 48 wasmade in each group; In vitro lymphatic ring strain measurementtechniques, tracing of lymphatic ring, with the difference of contractionfrequency reflecting the reactivity changes of lymphatic to concentration gradient NE (n=8), and with the maximum contraction force reflecting thecalcium sensitivity changes of lymphatic to concentration gradient Ca2+ inthe state of depolarization (n=8); application of calcium-sensitive enhancerAngiotensinⅡ(AngⅡ), calcium-sensitive inhibitor of insulin (Ins)incubation lymphatic ring 10 minutes, were observed the changes oflymphatic reactivity (n=16) and calcium sensitivity (n=16). Comparedwith sham group, the NE concentration-response curves of HS 1h and HS2h and calcium concentration-response curves in HS 2h were obviouslyshifted to the right and the reactivity of TD to NE and calcium, Emax andpD2 were markedly reduced (P<0.05, P<0.01). After being incubated withcalcium sensitizer AngⅡ, the lymphatic reactivity to NE and calciumsensitivity significantly increased in HS group (P<0.05, P<0.01), but stillreduced compared with Sham group. Insulin, a calcium sensitivityinhibitor, decreased the contractile response of lymphatic to NE and Ca2+(P<0.05,P<0.01).These results suggested that the lymphatic reactivity progressivelydeclined in the process of hemorrhagic shock. Moreover, a positivecorrelation was presented in the hypo-reactivity of LP and MAP to NE.Besides, this hypo-reactivity of LP to NE has been emerged before theappearance of vascular hypo-reactivity. The calcium desensitizationinvolved the pathogenesis of lymphatic hypo-reactivity. Hypo-reactivity ofLP and calcium desensitization were important mechanism for decreasedlymphatic contractility, and they may play an important role in thepathogenesis of shock.