RT Journal Article SR Electronic T1 EFFECTS OF LANTHANUM ON 45Ca MOVEMENTS AND ON CONTRACTIONS INDUCED BY NOREPINEPHRINE, HISTAMINE AND POTASSIUM IN VASCULAR SMOOTH MUSCLE JF Journal of Pharmacology and Experimental Therapeutics JO J Pharmacol Exp Ther FD American Society for Pharmacology and Experimental Therapeutics SP 415 OP 425 VO 177 IS 2 A1 FRANK R. GOODMAN A1 GEORGE B. WEISS YR 1971 UL http://jpet.aspetjournals.org/content/177/2/415.abstract AB In rabbit aortic smooth muscle lanthanum ion (La+++) differentially inhibited contractions induced by potassium (K+), norepinephrine (NE) and histamine (inhibition of K+ NE histamine) in a sequence that differed from that reported previously for Ca++ depletion (inhibition of K+ histamine NE) under similar conditions. Addition of 1.5 mM La+++ reduced the 45Ca tissue space and produced a sustained increase in 45Ca efflux from the isolated media-intimal layer of aortic muscles washed out in Tris solution containing no added Ca++. The addition of ethylenediamine tetraacetic acid or 1.5 mM Ca++ under analogous conditions elicited sustained increases in 45Ca efflux. Thus, it appears that La+++ acts at some superficial cellular sites in vascular smooth muscle to prevent reuptake or rebinding of Ca++ at these sites and to inhibit tension responses dependent upon release of Ca++ from these sites. These findings support the idea that the induction and maintenance of contractile responses by stimulatory agents depend upon the utilization of different Ca++ sites or stores in rabbit aortic smooth muscle. © 1971 by The Williams & Wilkins Co.