Dual effects of mesenteric lymph isolated from rats with burn injury on contractile function in rat ventricular myocytes

Abstract

Dual effects of mesenteric lymph isolated from rats with burn injury on contractile function in rat ventricular myocytes.

Cellular mechanisms of burn-related changes in contractility and its prevention by mesenteric lymph ligation

“…More recently, our studies have shown that the mesenteric lymph collected from rats with Ϸ40% TBSA burn injury (burn lymph) exerted concentration-dependent effects on the contractility of LV myocytes isolated from healthy rats. At lower concentrations (Ͻ0.5%), burn lymph increased the amplitude of myocyte contraction (38), whereas physiologically relevant concentrations (0.1-5%) of burn lymph reduced myocyte contractility (37). Taken together, these observations strongly suggest that burn injury promotes the mobilization or release of factor(s) in mesenteric lymph, which trigger abnormal myocyte contractility and that defective cardiomyocyte contractility contributes to burn-related cardiac depression.…”

“…Rats were deeply anesthetized (60 mg/kg pentobarbital sodium), and the heart from each rat was quickly removed as previously described (37,38). The heart was cannulated and perfused in a retrograde fashion via the aorta by the Langendorff method for about 3 min with a modified Ca 2ϩ -free Krebs-Henseleit solution containing (in mmol/l): 110 NaCl, 2.6 KCl; 1.2 MgCl 2, 1.2 KH2PO4, 25 NaH 2PO4, 11 glucose, 30 taurine, and 10 HEPES (pH 7.4), which was oxygenated by bubbling with 95% O 2-5% CO2.…”

“…Myocytes contraction (%cell shortening) was measured by video edge detection, as previously described (35,37,38). Briefly, isolated LV myocytes were perfused with Tyrode solution at 32°C.…”

“…Intracellular free Ca 2ϩ was monitored as the ratio of 340 -380 nm fluorescence of fura-2 using the Photoscan dual-beam spectrofluorophotometer (Photon Technology) as described previously (35,37,38). Cells were stimuated at 0.5 Hz, and the changes in Ca 2ϩ in the cells were depicted as changes in the ratio of 340/380 signal.…”

Mesenteric lymph duct ligation prevents trauma/hemorrhage shock-induced cardiac contractile dysfunction

“…Although we do not know what the biologically active factors are in T/HS lymph, we have excluded a number of putative candidates, including cytokines (9), bacteria, and bacterial products (2). Whatever the factors are in lymph, on the basis of our in vitro burn studies, burn lymph appears to exert a direct depressant effect on normal myocyte contractility and Ca 2ϩ transients that are similar to the changes observed in myocytes harvested from burned rats (39). Further studies investigating the effects of T/HS lymph on in vivo cardiac and in vitro myocyte contrac- Values are means Ϯ SE; n ϭ no.…”