PT  - JOURNAL ARTICLE
AU  - GEORGE B. WEISS
AU  - FRANK R. GOODMAN
TI  - EFFECTS OF LANTHANUM ON CONTRACTION, CALCIUM DISTRIBUTION AND Ca<sup>45</sup> MOVEMENTS IN INTESTINAL SMOOTH MUSCLE
DP  - 1969 Sep 01
TA  - Journal of Pharmacology and Experimental Therapeutics
PG  - 46--55
VI  - 169
IP  - 1
4099  - http://jpet.aspetjournals.org/content/169/1/46.short
4100  - http://jpet.aspetjournals.org/content/169/1/46.full
SO  - J Pharmacol Exp Ther1969 Sep 01; 169
AB  - In the longitudinal smooth muscle layer isolated from guinea-pig ileum, 1.8 mM lanthanum ion (La+++) inhibited both resting tone and contractions induced by either acetyicholine or 80 mM potassium ion. The equilibrated tissue space occupied by nonradioactive Ca++ or by Ca45 was reduced by La+++. Efflux of Ca45 was transiently increased by La+++ only in muscles not previously exposed to Ca++-containing solutions during washout. The actions of La+++ upon muscle contraction and Ca45 movements resembled those observed with high concentrations of Ca++. Increasing the proportion of bound Ca45 by incubating muscles in solutions containing Ca45 but no added Ca++ resulted in an increased inhibition of Ca45 uptake by La+++. Under these conditions, La+++ blocked a Ca++-induced shift of Ca45 from the slow to the fast washout component. La+++ also prevented a transient ethylenediamine tetraacetic acid-induced increase in Ca45 efflux. Thus, La+++ appears to replace Ca++ at superficial binding sites, to decrease the mobility of Ca++ located at other less superficial membrane sites and to prevent uptake of Ca45 to various cellular sites. Ca++ movements and Ca++ binding sites important for muscle contraction apparently involve different but interdependent cellular compartments which can be altered either directly or indirectly by La+++. © 1969, by The Williams & Wilkins Company