Investigations of metabolic parameters in male and female rats during the course of life

Abstract

In a large series investigation, a well-defined Sprague-Dawley inbred strain of male and female rats aged between 2 and 36 months (in 24 age groups) was kept and bred under standard conditions. Besides measurement of total body and organ weights, especially of absolute and relative weights for liver, spleen, lung, kidney, heart and for the brain, the following serum parameters were precisely registered using an automatic analyser: serum protein, uric acid, creatinine, cholesterol and triglycerides as well as serum lactate dehydrogenase (LDH), serum glutamic-oxaloacetic transaminase (SGOT), serum glutamic-pyruvic transaminase (SGPT), and alkaline phosphatase (AP). All values were obtained from 6–10 animals in each of the 24 age groups (the groups were of rats aged 2, 3, 4.5, 6, 7.5, 9, 10.5, 12, 13.5, 15, 16.5, 18, 19, 20.75, 22, 23.5, 25, 26.5, 28, 30, 31.5, 33, 34, and 35.5 months). In some cases double and triple series were investigated so as to obtain sufficient variation and to allow correlation-statistical analyses. The results show statistically significant age-related increases in cholesterol for male rats on ageing, for female rats only at the senile age. No increase in SGPT levels could be demonstrated in the male animals from the 12th month on. Furthermore, no age-dependent alterations were found for the serum total protein, uric acid, creatinine, triglycerides, LDH, SGOT, SGPT and AP. However, there were distinct sex-dependent differences: female animals exhibit higher serum total protein and triglycerides but lower levels of serum cholesterol, uric acid, LDH, SGOT, SGPT, and AP than male rats in the course of life. These results are important for theory, practice and clinical purposes. The findings are therefore discussed in connection with corresponding human values obtained for the above parameters.