AJP - Heart and Circulatory Physiology, Vol 233, Issue 1 114-H121, Copyright © 1977 by American Physiological Society
Action of adenosine and adenine nucleotides on dogs' isolated veins
R. H. Verhaeghe
Adenosine depressed norepinephrine contractions of dogs' saphenous vein
strips in both the presence and the absence of Ca2+ and after inhibition of
calcium influx by verapamil. It antagonized noncompetitively contractions
induced by Ca2+ in depolarized strips after alpha-adrenergic blockade.
Contractions obtained with acetylcholine were also depressed by adenosine.
This depression was not accompanied by an increase in cAMP or a decrease in
the elevated cGMP level. Thus the depression of the smooth muscle cell
reactivity still occurs in the absence of calcium influx and is not
mediated by the cyclic 3',5'-nucleotide system. Adenosine diphosphate and
triphosphate, but not adenosine (10(-6) to 10(-4) M), increased the basal
tension of resting saphenous strips. This was prevented by removal of
calcium from the bath. In contracted strips, lower concentrations of both
nucleotides (10(-6) to 10(-5) M) caused relaxation whereas with high
concentrations (10(-4) to 10(-3) M) further contraction occurred. Thus,
unlike adenosine, the adenine nucleotides facilitate calcium influx.
