RT Journal Article
SR Electronic
T1 An evaluation of the ability of a series of full alpha-1 adrenoceptor agonists to release internal calcium in venous smooth muscle.
JF Journal of Pharmacology and Experimental Therapeutics
JO J Pharmacol Exp Ther
FD American Society for Pharmacology and Experimental Therapeutics
SP 377
OP 381
VO 235
IS 2
A1 K F Jim
A1 R A Macia
A1 W D Matthews
YR 1985
UL http://jpet.aspetjournals.org/content/235/2/377.abstract
AB Our previous studies have shown that activation of postsynaptic alpha-2 adrenoceptors mainly utilizes extracellular calcium whereas activation of postsynaptic alpha-1 adrenoceptors mobilizes both extracellular and intracellular calcium to produce contractions in the canine saphenous vein. In the present study, the abilities of several full alpha-1 adrenoceptor agonists to release internal calcium for contractions in the canine saphenous vein were evaluated. Contractions to these alpha-1 agonists at two different equieffective concentrations (concentrations that produced 50 and 80% of the maximum phenylephrine response, PE50 and PE80, respectively) were determined in both zero external calcium medium and in normal calcium medium containing 5 mM La . If a correlation exists between the efficacy of an agonist and its ability to release internal Ca++, the contractile response to each agonist should be similar under these conditions. The results indicated marked variations in mechanical responses elicited by these alpha-1 agonists at both PE50 and PE80 concentrations. The data suggest a lack of correlation between efficacy and the ability to release internal calcium to induce contractions for a series of full alpha-1 adrenoceptor agonists in venous smooth muscle.