Changes in activity of hippocampus creatine kinase under circadian rhythm disorders

Abstract

We have studied the influences that prolonged isolation and disruption of the circadian cycle have on behavioral activity and hormonal status among animals. It has been showed that such conditions result in development of stress, and decreases occur in the activity of both isoforms of rat hippocampus creatine kinase (CK). We have established kinetic parameters (V_max, K_m) of this hippocampal enzyme and the nature of the modifications produced by the protocol. It has been suggested that prolonged isolation and disrupted natural circadian cycle result in lower CK-BB activity in animals due to structural changes in the enzyme and a decrease in ATP and creatine substrates. Lowered enzyme activity is accompanied by an accumulation of Ca²⁺ ions in the cell, and this might decrease activity of plasma membrane and mitochondrial Ca-ATPase.

Keywords:

• long-lasting stress
• brain
• hippocampus
• mitochondria
• creatine kinase
• Ca²⁺-ATPase