Lipolytic patterns in isolated adipocytes of continuously endotoxemic rats

Lipolytic patterns were studied in adipocytes isolated from rats after 6 and 30 hr of continuous Escherichia coli endotoxin (ET) or saline infusion via a subcutaneously implanted osmotic pump. By 6 hr, ET cells responded to norepinephrine (NE) stimulation with significantly greater increase above basal rates of glycerol and free fatty acid (FFA) release than did control adipocytes. By 30 hr of continuous infusion, basal glycerol release was enhanced; the in vitro lipolytic response evoked by NE was significantly reduced in ET cells compared to rates on the previous day, and NE-stimulated lipolysis in ET cells was significantly below that of controls. At the same time, the in vitro antilipolytic effect of insulin was attenuated. We conclude that 1) an initial metabolic response can be observed within a few hours of a continuous, low dose ET infusion, 2) the biphasic nature of the sequential changes in lipolysis is likely to reflect alterations in the hormonal environment in vivo, and 3) these features are consonant with some aspects of the metabolic profile of septic patients.