Mesenteric Lymph Return Is an Important Contributor to Vascular Hyporeactivity and Calcium Desensitization After Hemorrhagic Shock

Abstract

Vascular hyporeactivity is an important factor in irreversible shock, whereas calcium desensitization is one of the mechanisms of vascular hyporeactivity, and the intestinal lymphatic pathway plays an important role in multiple organ injury after severe hemorrhagic shock (HS). In this study, our aims were to determine the effects of mesenteric lymph on vascular reactivity during HS and the mechanisms involved. First, the in vivo pressor response was observed by intravenous injection of norepinephrine (3 μg/kg) at different time points after HS. We found that mesenteric lymph duct ligation (MLDL) and mesenteric lymph drainage (MLD) enhanced the pressor response at multiple time points after shock. Next, vascular reactivity and calcium sensitivity in superior mesenteric artery (SMA) vascular rings were examined using an isolated organ perfusion system. Vascular reactivity and calcium sensitivity were higher for SMA rings from rats that had undergone HS plus MLDL or MLD that those from rats that had undergone only HS. The effects of MLDL and MLD on vascular reactivity and calcium sensitivity were significantly increased following incubation with the calcium sensitizer angiotensin II and were reduced after incubation with the calcium sensitivity inhibitor insulin. When SMA rings from normal rats were incubated with mesenteric lymph from rats subjected to HS, lymph obtained 0 to 0.5 h after shock enhanced vascular reactivity and calcium sensitivity, whereas lymph obtained 1 to 3 h after shock blunted these effects. We finally examined vascular reactivity and calcium sensitivity in HS rats subjected to MLD at 0 to 3 h or 1 to 3 h after shock. We found that contractile activity of SMAs in response to norepinephrine or Ca was higher in HS rats subjected to MLD at 1 to 3 h after shock compared with rats subjected to MLD at 0 to 3 h after shock. These results indicate that mesenteric lymph return plays an important role in biphasic changes in vascular reactivity during HS. Even more importantly, mesenteric lymph 1 h after shock was an important contributor to vascular hyporeactivity, and its mechanism of action was related to calcium desensitization. Targeting lymph may therefore have therapeutic potential in the treatment of severe shock-induced hypotension.

Role of protein kinase G on the post-shock mesenteric lymph blockage ameliorating vascular calcium sensitivity

“…Meanwhile, after SMA rings in shock+ligation groups incubated with KT5823, the response to gradient Ca 2+ was remarkably increased. Using the technique of vascular ring strain measurement in vitro, we found that the calcium sensitivity of SMA in shock group was significantly reduced compared with sham group, the calcium sensitivity of SMA in shock+ligation and shock+drainage groups were significantly increased than that of shock group at several concentration points, these results are consistent with our previous study 5 Our previous experiments found that there were effects of Rhokinase, PKC on blocking the return of PSML improving calcium sensitivity, respectively 12,13 . But, whether there are interaction effects among these signal molecules during the PSML decreasing the calcium sensitivity following hemorrhagic shock, it still not clears.…”

“…Rats in the shock, shock+ligation and shock+drainage groups were hemorrhaged from the left femoral artery to produce a MAP of 40 mmHg within 10 min, slowly and uniformly. The MAP was maintained at 40±2 mmHg for 3h by withdrawing or returning shed blood as required for the preparation of hemorrhagic shock model 3,5,7 . When the MAP reached 40 mmHg, the mesenteric lymph duct was ligated in rats in the shock+ligation group; the mesenteric lymphatic duct was cannulated for lymph drainage using a homemade bending needle in rats in the shock+drainage group.…”

“…The vascular hyporeactivity is an important factor in irreversible shock 2 , meanwhile calcium desensitization is one of the mechanisms of vascular hyporeactivity 3,4 . Our previous study showed that the mesenteric lymph duct ligation (MLDL) and mesenteric lymph drainage (MLD), which blocking the post-shock mesenteric lymph (PSML) return, both improved the reactivity and calcium sensitivity of vascular rings isolated from severe hemorrhagic shock rats 5 . But the mechanism by which PSML blunts the vascular reactivity and calcium sensitivity remain unclear.…”

Post-hemorrhagic shock mesenteric lymph is an important contributor to cardiac dysfunction following hemorrhagic shock

“…Under aseptic conditions, all of the rats received femoral operations to separate the right femoral vein and bilateral femoral arteries for anticoagulation, hemorrhage, and monitoring of mean arterial pressure (MAP) as previously reported 10 . Afterwards, the rats received abdominal operation to separate the mesenteric lymph duct from the surrounding connective tissues for the drainage of PSML.…”

“…In the shock+drainage group, the mesenteric lymph drainage was performed from 1 h to 3 h of hypotension as previously described 10 , the PSML were centrifuged at 315 g at 0-4°C for 5 min to remove all cellular elements and flash frozen at -75°C in refrigerator (Thermo Electron, Waltham, MA) for the further experimentation.…”