Vascular Reactivity of Rat, Guinea‐pig, Rabbit and Human Vessels to Bufadienolides and Cardenolides

Abstract

Cardenolides and bufodienolides are Na+-K+-ATPase (NKA) inhibitors. The aim of the present study was to evaluate the response to such compounds of vessels from different species in order to compare potency and efficacy. The experimental protocols were approved by the Animal Care and Ethics Committee of the Ceara State University. The aortic rings and mesenteric artery for isometric recordings of contractions in response to cumulative addition of OUA, BUF, DIG (0.1-100 µM). The contractions were expressed as percentage of the maximal contraction elicited by phenylephrine. Ouabain, up to 100 µM, promoted no contraction in rat aorta but promoted a slow onset contraction that attained a maximum of 71.5±14.8% and 101.2±8.5% in guinea-pig and rabbit tissue, respectively. Bufalin promoted slow onset contractions after 30 and 100 µM that reached a maximum of 20.6 ± 5.2%,55.0±10.5% and 94±19.8% in tissues gathered from rats, guinea-pigs and rabbits, respectively. On the other hand, digoxin did not elicit contraction in rabbit or rat aortic rings but elicited a similar slow onset that attained its maximum after more than 50 minutes and reached 79.7±15.6% in guinea-pig tissues. In human aortic rings in response to 100 µM bufalin or ouabain reached a maximum of 96.7±24.4% or 140±26.7%, respectively. In the 2nd branch of the mesenteric artery, BUF promoted a slow contractile response (46 % ± 9.6 %) only at a dose of 100 µM.Pretreatment with guanethidine (GUA + BUF) significantly attenuated BUF vasoconstriction in aortic rings (39.7% ± 8.4) and prazosin (1µM) completely blocked the contraction, suggesting and indirect noradrenergic activation.