Биологические науки/ 8. Физиология человека и животных

Dr. Sci. Biol., Prof. Bebyakova N.A., Cand. Biol. Sci., Ass. Рrof. Kuritsin S.N., graduate Shabalina I.A.

Northern State Medical University, Arkhangelsk, Russia

Participation of opioid peptides in the regulation of stress vasoconstriction

Stress-limiting system opioid peptides (OP) has an important role in limiting stressful hemodynamic changes. Endogenous opioid system is represented by opiate receptors (OR): μ, δ and κ, OP (enkephalins, endorphins, dinorfins, etc.), enzymes of biosynthesis and cleavage of OP. By limiting the negative effects of stress, OP have high cardiovascular activity. The role of OP in the peripheral vascular tone is insufficiently studied, despite the fact that in the endothelium of blood vessels in these types of ORs were found.

In this regard, in conditions of acute stress studied the role of activation of different types of ORs in the regulation of peripheral vascular tone (PTA) in conditions of acute stress. Experiments were performed on male rats of the keepers of Wistar, characterized vasoconstrictor response to acute stress, which is modeled by placing the animal at 1 hour in the immobilization chamber without rigid fixation. PTA evaluated by reovazogramms rat tail artery, using indicators of peripheral resistance index (PRI), the elastic modulus (EM), an index of rapid hyperemia (IRH). Reovazogramms filmed using a multifunction computer diagnostic complex "Diastemata - 01".

As a non-selective agonist of μ-and δ-OR, a synthetic analogue of leu-enkephalin - dalargin; for selective activation of μ-OR used a synthetic analogue of met-enkephalin - DAGO, for selective activation of δ-OR - a synthetic analogue of leu-enkephalin - DSLET, for activation of κ-OR - dinorfin A 1-13. OP was administered at a dose of 100 mg / kg intraperitoneally for 5 min before stress in 0.9 ml of Ringer's solution. Blockade of ORs performed with naloxone - their non-selective antagonist, which injected a similar manner at a dose of 700 mg / kg.

The animals in the control series for the duration of immobilization, the authentic growth of PTA, which is reflected in an increase to the 60th min of stress PRI to 84,3% (p<0,001) and decrease in EM at 32,2% (p<0,001), and IRH by 18,4% (p<0,001) compared with 5 min of stress. Thus, it is found that under conditions of acute stress, there is a pronounced increase in vascular tone, is changing the elasticity of blood vessels of different diameter, but large vessels are characterized by more pronounced changes in acute stress.

Participation of OP in modulating stress vasoconstriction was established by blockade OR of naloxone. Under these conditions, there was more pronounced compared to the control vasoconstrictive response, which was accompanied by an increase in the rate of growth stressful PRI and more pronounced decrease in the elasticity of small blood vessels compared with large: PRH 60th min of the experiment was at 33,2% higher than in the controls (p<0,001), respectively IRH below to 38,3% (p<0,001), and EM - 14,9% (p< 0,01) similar indicators in the control.

Introduction of selective and nonselective agonists ORs showed that they all have a protective effect on stress vasoconstriction with varying degrees of severity. The greatest protective effect associated primarily with changes in the elasticity of large vessels during the entire experiment, was observed upon activation of μ-OR and concomitant activation of μ-and δ-OR. For selective activation of δ-OR revealed a protective effect from 15th min of the experiment, whereas activation of κ-OR led to a short-term protective effect only at the 15th min of stress (Fig. 1).

Of particular interest to study the protective effect of changes in conditions of PTA acute stress of dalargin (D-Ala²-Leu⁵-Arg⁶-enkephalin). Dalargin is the first domestic pharmaceuticals, established on the basis of OP (approved by the Pharmacological Committee of the Public Health Ministry 09.03.82). The drug shows almost equal affinity for μ-and δ-OR and does not interact with other types of OR. Revealed that dalargin has a positive effect on the cardiovascular system under stress. It found that in the early stages of myocardial ischemia drug prevents a sharp drop in blood pressure. In addition, it is proved that dalargin possesses a strong cardioprotective effect during immobilization stress in rats. The features dalargin are high hydrophilicity and polarity of its molecule that does not allow him to penetrate the blood-brain barrier in doses of less than 200 mg / kg.

Against the background of the introduction of PTA dalargin stressful growth was less pronounced than in the controls. By the 60th min of stress PRI increased by 64,9% (p<0,001) compared with the 5th min of immobilization. Already at the 5th min of stress PRI in this series was by 23,3% lower compared with control (p<0,001), and at the 60th min immobilization - lower by 14,6% (p<0,01). This observed more pronounced changes in elasticity of blood vessels of large diameter. To the 60th min of stress EM decreased by 28,3% compared with the 5th min of the experiment (p<0,001), higher than the control values at 47,2% (p<0,001). IRH the 60th min declined only 22,3% (p<0,001), that only 26,4% above control values (p<0,001).

The results of the study show promise for further study of dalargin to identify the optimal dose of the drug and its use for treatment and prevention stressful changes in vascular tone, but significant drawback is the rapid biodegradation of the molecule under the action of peptidases. In this regard, we studied the synthetic analogue of dalargin, a molecule which has been modified NH-group (D-Ala²-Leu⁵-Arg⁶-enkephalin-NH₂), which increased the half-life. It was found that the protective effect of dalargin stabilized with the aminogroup, as compared to his first analogue above the 5th and 15th min of stress. PRI with the introduction of D-Ala²-Leu⁵-Arg⁶-enkephalin-NH₂ under conditions of acute stress on 16,0% lower than with the introduction of D-Ala²-Leu⁵-Arg⁶-enkephalin for 5 min of stress, and 4,9% in 15 min. Since the 30th min and the end of the experiment, significant differences have been detected. Consequently, in rats given genetic lines under acute stress, D-Ala²-Leu⁵-Arg⁶-enkephalin has a maximum protective effect of PTA in the first 5 min after administration, holding stressful change the PRI, and the introduction of D-Ala²-Leu⁵-Arg⁶-enkephalin-NH₂ lengthen the maximum protective effect up to 15 min.

Thus, the need to further study the modulating effect of dalargin and its stable synthetic analogs to create on their basis of pharmacological agents that can modulate the PTA, and, consequently, blood pressure. That could make a contribution to the study and prevention of such social diseases as hypertension.

Work is maintained by the grant of the Russian Fund of Basic Researches № 08-04-98817.