Abstract:
Vasopressin known as antidiuretic hormone is responsible for regulating plasma osmolality and volume. It acts as a neurotransmitter in the brain to control circadian rhythm, thermoregulation, and adrenocorticotrophic hormone release. The therapeutic use of vasopressin has become increasingly important in the critical care environment in the management of cranial diabetes insipidus, bleeding abnormalities, oesophageal variceal haemorrhage, asystolic cardiac arrest, and septic shock.
The present study aims toward identifying similarities and differences between the resistance arteries belonging from various mammal species that are most involved in veterinary practice: rats, cats and dogs.
Smooth muscle has been studied as circular preparations from rat aorta, cat and dog coronary gastric aorta. Force generation has been studied using isometric transducers while stimulation of preparations was made pharmacologically at various doses. Results were expressed as percentage of inhibition or stimulation of the control contraction.
Force generation, frequency and amplitude of spontaneous contraction have been
recorded. Administration in isolated preparations where made using desmopressin acetate (Ferring) as vials of 4 mg/ml. The preparation is a synthetic analogue of the natural hormone 8-arginine-vasopressin, as arginine-vasopressine-monoacetatetrihydrate. Dosages varied from 10-12M to10-8M. Several methods have been tried for normalizing maximal isometric force developed by smooth muscle from various locations, vessel dimensions and animal species. We have measured in vitro the amount of force generated by arterial rings harvested from the same areas, very rigorously cleaned of adventice and surrounding tissues and the force, expressed as mN was ratioed to the wet weight of the preparations.
The results were statistically investigated using the t-test and ANOVA testing. In preparations of rat aorta and splachnic arteries from cat and dog, the vasopressin induced a tonic contraction, with an aspect of descending plateau.
In conclusion, vasopressin contraction has several special characteristics concerning its dynamics. The contractile plateau is kept only for about 10-15 minutes, after which it fades, and new administration in a space of approximately 16 minutes does not induce the initially effect (probable tachyphylaxis).
