Comparison of GH-stimulation by GH-RH(1-29)NH2 and an agmatine29 GH-RH analog,after intravenous,subcutaneous and intranasal administration and after pulmonary inhalation in rats

Many studies have shown that human GH-RH(1-29)NH₂ possesses full intrinsic activity of GH-RH(1-44)NH₂in vitro and in vivo. This investigation was performed to evaluate the efficacy of GH-RH(1-29)NH₂ given by different routes of administration in stimulating GH release in rats. In each case GH-RH(1-29)NH₂ was administered intravenously, subcutaneously, intranasally and by pulmonary inhalation at two different doses to groups of seven male rats. At a dose of 150 μg/kg GH-RH(1-29)NH₂, the magnitude of GH response was significantly higher for the pulmonary inhalation group (355 ± 33.2 ng GH/mL) than for the subcutaneous group (246 ± 36ng GH/mL) or for the intranasal group (175 ± 30ng GH/mL). The group injected intravenously with GH-RH(1-29)NH₂ at a dose of 2.5 μg/kg showed the highest response, GH levels reaching 877.2 ± 115 ng/mL. A similar pattern of responses was obtained for the superactive GH-RH(1-29) agmatine²⁹ analog, MZ–3-149, at doses that were 50 times lower. Our results indicate a high bioavailability of GH-RH(1-29)NH₂ or analog MZ-3-149 administered by a convenient pulmonary inhalation route. The GH-releasing effect of GH-RH(1-29)NH₂ or analog MZ-3-149 delivered by pulmonary inhalation is superior to subcutaneous and intranasal administration.     

Sustained Monomorphic Ventricular Tachycardia: A Single Electrocardiographic Expression of Different Patterns of Reentry

Sustained monomorphic ventricular tachycardia (SMVT) can be the electrocardiographic expression of a reentrant impulse in the ventricles. In this study we analyzed the different types of reentry that might lead to SMVT, Methods: The pattern of activation of 73 episodes of SMVT induced in thin sheets of epicardium in 50 Langendorff perfused rabbit hearts were visualized with high resolution epicardial mapping (248 points). Results: Five different patterns of reentry resulting in SMVT were identified: (1) Single-loop reentry around a fixed obstacle (n = 40); (2) Single-loop reentry around a functional arc of conduction block (n = 17); (3) Double-wave reentry around a fixed obstacle (n = 9); (4) Figure-of-eight reentry around two areas of functional block (n = 5); and (5) Multiple synchronized circuits around multiple areas of functional block (n = 2), Conclusion: SMVT is a single electrocardiographic expression of different patterns of reentry. Accurate mopping is mandatory to identify the reentrant pathway and the pathophysiological substrate of the arrhythmia.