Effect of enkephalins on energy potential of the liver and cerebral cortex of rats in the early period of traumatic shock

Abstract

Investigation of endogenous opioid peptides has demonstrated their ability to exert an antishock, anti-ischemic, and antistressor action [2, 7, 8]. These facts provided a basis for the present invesitgation, the aim of which was to study the effect of a synthetic analog of Leu-enkephalin on the energy potential of the brain and liver in the early period of traumatic shock. }~THODS Experiments were carried out on 86 male albino rats weighing 180-220 g. A model of traumatic shock was created by applying forceps to both hind limbs of the rats [5] for 3 h. The synthetic Leu-enkephalin analog D-Ala2-Leub-Arg6-enkephalin (synthesized in the Laboratory of Peptide Synthesis, All-Union Cardiologic Scientific Center, Academy of Medical Sciences of the USSR, Director Dr. Chem. Sci. M. I. Titov) was injecte@ intraperitoneally in a single dose of 500 Bg/kg body weight i0 min after the beginning of crushing. Intact rats served as the control. The animals were decapitated i h after removal of the forceps. All experiments were performed under superficial ether anesthesia. Weighed samples of liver and cerebral cortex were quickly transfered into liquid nitrogen. Concentrations of adenine nucleotides in the tissues were determined by enzymic methods: ATP with the aid of phosphoglycerate kinase, ADP and AMP in the course of successive reactions involving pyruvate kinase, lactate dehydrogenase, and myokinase [i]. The reagents were obtained from Boehringer (West Germany). Optical density was measured on a Specord M-40 spectrophotometer (East Germany). The energy charge (EC) of the adenine-nucleotide system was calculated by Atkinsonls formula [I0]. RESULTS The experiments showed that crushing the rats' hind limbs for 3 h led to a fall of 33.6% in the ATP concentration in the cerebral cortex (Table i). The ADP level in the brain tissues increased by 21.3%, and the AMP level by 4.1% compared with the control. The value of EC in the group of rats with traumatic shock, but untreated, was lower than in intact animals. Shock trauma caused a reduction of the ATP concentration in the animals I liver by half. The ADP concentration in these animals increased by 39.4% and the AMP by 20.5% compared with the control. The value of EC also was lower than in the control.