The effect of chronic hypoxia on in vitro lipolysis in the rat

Abstract

The responsiveness of the lipolytic system in chronically hypoxic rats (14 500 ft) was assessed by the in vitro release of free fatty acids (FFA) and glycerol, measured aerobically and anaerobically, in epididymal fat pads from fed, fasted, and fasted–refed animals. Basal aerobic release of FFA for fed rats was significantly higher in the altitude (ALT) group. In fasted rats both basal and norepinephrine (NE)-stimulated release of FFA and glycerol was higher when compared with heavier sea level (SL) controls. However, weight-matched (younger) controls showed no difference in release rates. Anaerobic NE-stimulated release of FFA, glycerol, and lactate was higher in ALT rats than in weight-matched SL controls only in those animals fasted and refed a high carbohydrate diet. Fat pad glycogen content in such animals was 0.207 mg/100 mg tissue for SL and 0.384 for ALT. Anaerobic in vitro FFA mobilization in adipose tissue from fasted–refed ALT rats is more sensitive to NE, and this physiological advantage may be a reflection of a greater potential for glycogen storage in the fat tissue of these acclimated animals. Additionally, weight matching is necessary in evaluating altitude-stressed animals, and use of dietary restrictions to obtain controls of equal age and weight may yield misleading metabolic data.