Biol Pharm Bull 1999 Dec 01;2212:1279-83. doi: 10.1248/bpb.22.1279.

The inhibitory effect of the toxic fraction from sea urchin (Toxopneustes pileolus) venom on 45Ca2+ uptake in crude synaptosome fraction from chick brain.

???displayArticle.abstract???
The effects of toxic peaks (P-I, P-II and P-III eluted from Sephadex G-200 column) from the sea urchin Toxopneustes pileolus on time-dependent 45Ca2+ uptake in chick P2 fraction (crude synaptosome fraction) were studied under physiological ionic conditions. Time-dependent 45Ca2+ uptake was inhibited by P-II and P-III, but not by P-I. P-II had the greatest inhibitory effect. The inhibitory effect of P-II was not due to the inhibition of 45Ca2+ binding on P2 fraction, because P-II did not affect 45Ca2+ binding in osmotic-shocked P2 fraction. P-II did not affect KCl-stimulated 45Ca2+ uptake in P2 fraction, (Ca(2+)-Mg2+)-ATPase activity in the synaptic plasma membrane (SPM) fraction, or (Na(+)-K+)-ATPase and Mg(2+)-ATPase activities in osmotically-shocked P2 fraction. In contrast, the Na+/Ca2+ exchanger blocker 2'',4''-dichlorobenzamil (DCB; 100 microM), with a poor specificity, inhibited not only time-dependent 45Ca2+ uptake but also KCl-stimulated 45Ca2+ uptake, (Ca(2+)-Mg2+)-ATPase, Mg(2+)-ATPase and (Na(+)-K+)-ATPase. Involvement of Na(+)-Ca2+ exchanger in the time-dependent 45Ca2+ uptake was ruled out, since it was not inhibited by replacement of Na+ with Li+ in reaction medium. These results suggested that the inhibition by P-II on time-dependent 45Ca2+ uptake appeared to be more specific than the commercially available Na+/Ca2+ exchanger blocker DCB, although the mechanism is not clear yet.

???displayArticle.pubmedLink??? 10746155
???displayArticle.link??? Biol Pharm Bull


Genes referenced: LOC100887844 LOC581395