Evidence for an early lipid soluble cardiodepressant factor in rat serum after a sublethal dose of endotoxin.
The administration of a sublethal dose of E coli endotoxin (2 mg/kg) has been found to induce in the intact rat a slight decrease in mean carotid arterial pressure only 16 hours later. No death occurred whereas the same dose injected in the adrenalectomized rat caused lethality, and so did the higher dose (3 mg/kg) in the intact rat. Sera sampled two, four and 16 hours after administration of endotoxin (2 mg/kg) depressed contractile activity and the chronotropic response of isoproterenol in cultured rat heart cells. Such properties were not noted with sera sampled one or 24 hours after endotoxin administration. These cardiodepressant effects were localized in the lipid soluble fraction of endotoxin serum and absent in the fat-free portion. And yet neither endotoxin nor nonesterified fatty acid (NEFA) serum fraction was involved, since they did not alter cell culture activity. Moreover, though total or individual NEFA levels in endotoxic serum were higher than those of control rat serum four hours after endotoxin injection, they were not significantly different from control 16 hours later. It is concluded that the administration of a sublethal dose of endotoxin to the intact rat induces early and prolonged (up to 14-16 hours) release of one or more humoral lipid soluble cardiodepressant factor(s), even in the absence of systemic hypotension.
D000315:Adrenalectomy; D000818:Animals; D001794:Blood Pressure; D003864:Depression, Chemical; D004731:Endotoxins / Q000633:toxicity*; D005230:Fatty Acids, Nonesterified / Q000097:blood; D006321:Heart / Q000187:drug effects*; D006339:Heart Rate / Q000187:drug effects; D066298:In Vitro Techniques; D007545:Isoproterenol / Q000494:pharmacology; D008055:Lipids / Q000097:blood*; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects; D051381:Rats; D012772:Shock, Septic / Q000097:blood*; D012995:Solubility
D004731:Endotoxins; D005230:Fatty Acids, Nonesterified; D008055:Lipids; D007545:Isoproterenol