The effects of immobilization stress on serum triglycerides, nonesterified fatty acids, and total cholesterol in male rats after dietary modifications.

The effects of acute immobilization stress on triglycerides, nonesterified fatty acids (NEFA) and total cholesterol were determined in serum samples obtained by indwelling jugular catheters from male Sprague-Dawley rats. Stress was evaluated in three groups of rats: (1) those maintained on a regular Purina Chow diet and then fasted for 24 hours; (2) those maintained on this same diet but not fasted (nonfasted) before experimentation; and (3) those maintained on a Purina Chow diet supplemented with cholesterol (1%) and fat (10%) for 6 weeks and nonfasted prior to experimentation. Samples were taken by catheter in the home cage prior to, four times during a one hour stress/nonstress period and thirty minutes after being returned to the home cage for recovery. Nonstressed rats remained in the home cage during the entire 90 minute period. In each dietary state studied, stress affected serum triglycerides and NEFA but not total cholesterol levels. Triglyceride levels in fasted rats increased during the stress period. On the other hand, triglycerides decreased in response to stress in nonfasted rats. In stressed, nonfasted high cholesterol-fed animals, triglycerides were elevated in comparison to their nonstressed counterparts. In both fasted, regular diet-fed and nonfasted, cholesterol-fed rats, NEFA sharply declined from baseline after 5 minutes of stress; NEFA did however increase after fifteen minutes. NEFA levels in both stressed and nonstressed, nonfasted rats also rapidly decreased from baseline and never recovered throughout the session. Total cholesterol did not change in response to stress or dietary modifications. The rats maintained on a high cholesterol diet showed only a diet-induced increase in total cholesterol. Thus, acute immobilization stress affected serum triglyceride and NEFA values and these effects were diet- and time-dependent. Total cholesterol levels were unaffected by stress.