Effect of cortisol on gluconeogenesis in goats

Three non-pregnant goats of local Malaysian breed with body weights between 15.9 and 22.6 kg were arranged in a 3 x 3 Latin square design to study the effect of daily cortisol injections for 5-6 days on gluconeogenesis. The treatments consisted of cortisol injection at a daily level of 1 mg/kg BW (body weight), 2.5 mg/kg BW, and a control. An extra goat (14.0 kg) received the same treatments for comparison and to check the accuracy of the methods employed. NaH14CO3, preceded by a primer dose, was infused continuously for 4-5 h to estimate quantitatively the extent to which gluconeogenesis may be affected by cortisol administration. Glucose-2-3H was also injected as a single pulse to assess kinetic parameters of the glucose pool. There was strong tendency (P=0.08) indicating that cortisol administration increased plasma glucose concentration. The mean increases above pre-treatment levels were 6.6, 21.3 and 53.5 mg/100 ml plasma for control, low and high cortisol treatment respectively. The transfer quotient from CO2 to glucose for the treatments was significantly different (P<0.01) with mean values of 10.11, 12.10 and 14.41% for control, low and high level cortisol respectively. Since glucose flux was not significantly different among treatments, 2.39, 2.69 and 2.47 mg/min per kg BW being the mean values for control, low and high cortisol respectively, the rate of gluconeogenesis involving CO2 fixation expressed in absolute amounts was not significantly different among treatments (0.24, 0.33 and 0.36 mg/min per kg BW for control, low and high cortisol doses respectively). The insignificant result of the statistical test seemed to be caused by the low precision inherent in the experimental design. The data also show that glucose utilization was not impaired following cortisol treatment, and rather suggest normal glucose utilization at a higher level of plasma glucose concentration. (author)