Comparison of selective arginine vasopressin V1 and V2 receptor antagonists on burn shock in the rat

STUDY OBJECTIVE

Two selective V1 and V2 receptor antagonists of arginine vasopressin, d(CH2)5Tyr(Me)AVP and d(CH2)5[D-Ile2, Ile4, Ala9-NH2]AVP, were given intravenously in burn shocked rats to investigate the respective effects of V1 and V2 receptor blockade on the haemodynamic variables in burn shock.

DESIGN

Computer assisted on line real time measurements of mean arterial blood pressure, diastolic blood pressure, left ventricular systolic pressure, dP/dtmax, and heart rate were used to study the effects of the receptor antagonists during burn shock. In addition, the radioactive microsphere method was used to measure the changes of cardiac output and regional blood flows to heart, kidney, and liver in response to the antagonists during burn shock. Third degree burns extending over 30% of body surface area were made by dipping the rat's shaved back into water at 100 degrees C for 20 s.

EXPERIMENTAL MATERIAL

Male Sprague-Dawley rats (250-300 g) were used in groups of 6-9 per experiment.

MEASUREMENTS AND MAIN RESULTS

Mean and diastolic arterial blood pressures, left ventricular systolic pressure, dP/dtmax and heart rate were measured for 8 h after burns. Cardiac output and regional blood flow were measured at 3 h and 8 h postburn. Results showed that blockade of V1 receptor lowered mean and diastolic arterial blood pressures throughout the 8 h period, and raised left ventricular systolic pressure and dP/dtmax only during the early phase of shock. Cardiac output and blood flows to heart, kidney, and liver were increased by the V1 antagonist at 3 h but not at 8 h postburn. The V2 receptor antagonist increased mean and diastolic arterial blood pressures, left ventricular systolic pressure, and dP/dtmax both during the early and during the late phases of burn shock. It also improved cardiac output and blood flows to the heart, kidney, and liver during the early and late phases of burn shock. However, heart rate was not affected by V1 and V2 receptor antagonists.

CONCLUSIONS

The V2 like receptor may be the dominating receptor mediating vasopressin's inhibitory effect on the heart. V1 receptor mediated coronary vasoconstriction contributes to the myocardial depression possibly only at the compensatory phase of shock. In addition V1 receptor mediated vasoconstriction is important in maintaining blood pressure during burn shock.

Effect of peripheral injection of arginine vasopressin and its receptor antagonist on burn shock in the rat

To investigate the effect of arginine vasopressin (AVP) in the peripheral circulation on burn shock in the rat, AVP and its nonselective V1/V2 receptor antagonist d(CH2)5Tyr (Et)VAVP were administered intravenously in burn shocked rats. Cardiovascular parameters were recorded including left ventricular systolic pressure (LVSP), +/- dP/dt max, total area of the cardiac force loop (Lo), mean arterial blood pressure (MAP), heart rate (HR) and electrocardiogram (ECG). Our results showed that AVP failed to increase MAP in burned rats whereas it elicited a greater fall in LVSP, +/- dP/dt max and Lo and MAP than seen in control burned rats and hastened the onset of the decompensatory phase of burn shock resulting in the early death of burn shocked animals. The receptor antagonist d(CH2)5Tyr(Et)VAVP elevated LVSP, +/- dp/dt max and Lo for the eight hour observation period, and allowed MAP to recover from the initial profound fall following burn injury. Furthermore, it prolonged the survival time of the burned rats. AVP treated rats also displayed earlier abnormal changes such as elevation of S-T segment, inversion of T wave and ventricular fibrillation in ECG. The onset of these changes was much delayed in antagonist treated rats.

Possible involvement of beta-endorphin in the deteriorating effect of arginine vasopressin on burn shock in rats

The effect of intracerebroventricular injections of arginine vasopressin (AVP) on burn shock in the rat and its possible mechanism were explored in this study. AVP was administered intraventricularly at 30 min intervals (50 ng) in the burned rats. The arterial pressure and electrocardiogram (ECG) were recorded with a multipurpose polygraph before and after burn. Compared with the control, the MAP of the rats in the AVP group was elevated at the initial stage and fell dramatically at the late stage of burn shock with a higher mortality. The ECG of the rats in the AVP group also displayed earlier changes such as elevation of S-T segment, inversion of T wave, and ventricular fibrillation. These findings suggest an unfavorable role of AVP in burn shock. The plasma, hypothalamic, and anterior and posterior pituitary levels of beta-endorphin 3 hr after burn were measured by radioimmunoassay. The increased level of beta-endorphin in the plasma after AVP treatment indicates the possible involvement of beta-endorphin in the deteriorating effect of AVP on burn shock.

Chromosomal site of hepatitis B virus (HBV) integration in a human hepatocellular carcinoma-derived cell line

The single site of integration of hepatitis B virus in the human hepatocellular carcinoma cell line Hep 3B 2-1/7 was found to segregate with human chromosome 12 in somatic cell hybrids. Analysis of metaphase spreads of Hep 3B 2-1/7 following in situ hybridization with pHBV revealed integration at 12q13----q14, a location that coincides with a fragile site, fra (12q13). The possible significance of this location to the development of hepatocellular carcinomas is discussed.

THE USE OF POLYACRYLAMIDE GELS FOR CHROMATOGRAPHY OF PROTEINS

Sixteen copolymers of acrylamide and N,N′-methylene bisacrylamide were synthesized using ammonium persulfate and dimethylaminopropionitrile as initiators. The water regain values of these gels were found to increase with decreasing total monomer concentration and with decreasing N,N′-methylene bisacrylamide/acrylamide ratio. The partition coefficients (Kd) of a variety of compounds of molecular weights between 104 and 580 000 were determined by normal elution column chromatography for three gels. The Kd values for a given solute using different gels were found to increase with decreasing total monomer concentration of the gel and with decreasing N,N′-methylene bisacrylamide/acrylamide ratio. For various solutes through the same column, the Kd values varied linearly with the logarithms of the corresponding molecular weights over the Kd range of 0.1 to 0.6. However, a number of compounds showed deviations from this relationship.