SUSPENSION HYPOKINESIA IN RATS - EFFECTS OF THE TIME OF DAY ON METABOLIC AND HORMONAL CHANGES

Suspension hypokinesia is a new model which can simulate some effects of microgravity on the organism of laboratory animals. Two groups of m ale SPF-bred Wistar rats were suspended for 24 h. In the first group h ypokinesia began in the morning (M) (1 h after light onset, 0800 h), w hereas the other group was subjected to this treatment from the evenin g (E) (1 h after dark onset, 2000 h). In the serum, there was a statis tically significant increase In non-esterified fatty acids, triacylgly cerols (TG) and glucose and a decrease in triiodothyronine concentrati on in the M group, while only a significant increase in phospholipids (PL) was found in the E group. The serum corticosterone level was incr eased in both groups, more markedly in the M group. There was an Incre ase in TG and PL in the liver in M rats. In the bone marrow (femur), a n increase of triglycerols in E rats and an increase of phospholipids in M rats were found. The concentration of glycogen in the heart muscl e, m. quadriceps femoris and m. soleus rose in the M group only. The c hanges in the analyzed parameters predominate in the rats subjected to hypokinesia in the morning period. This fact confirmed the hypothesis about a higher sensitivity of rats to the stressor acting in the peri od of inactivity.