Comparative study of vascular arterial reactivity in several mammal species: 1. Reactivity of the arterial smooth muscle to vasoconstrictor agents

Abstract

Vascular reactivity is one of the three pillars on which lies the regulation of arterial pressure in living organisms. Arterial pressure is one of the main determinants of the activity state of various organs and systems both in healthy and in pathologically-altered states. The present study aims at identifying similarities and differences between the resistance arteries belonging from various mammal species that are most involved in veterinary practice: rats, cats, dogs and horses. The arterial fragments harvested from animals dead due to various clinical and traumatic conditions unrelated to vascular pathology were normalized using a newly-introduced system of quantification, the force index system. This has been calculated using the wet-weight parameter and the force generated after administration of various pharmacological agents that cause vasoconstriction. The artery fragments were fitted in organ baths using the Krebs-Henseleit saline, thermostated at 37° C and bubbled with a mixture of 95% O2 and 5%CO2. Vascular endothelium was either kept or removed using gentle rubbing with moist filter paper. Control of endothelial removal was made both functionally, using carbachol (synthetic derivative of acetylcholine) and microscopically, after testing. The force generated was measured using isometric force transducers coupled to a computerized acquisition system. The pharmacological vasoconstricting agents used were phenylephrine (synthetic derivative of epinephrine), KCl (potassium chloride 40-80 mM, as depolarizing agent) angiotensin II, and vasopressin. The results were statistically investigated using the t-test and ANOVA testing. The preliminary results show a dependence of the force generated an the amount of muscle present in the various species from which the arteries were taken, a specifically increased response of feline-derived arteries to angiotensin and a specifically increased response of canine-derived arteries to vasopressin. These results will be used as controls for further testing in various pathological conditions and for various other pharmacological agents used in the therapy of vascularly-induced pathological states.