Inhibition of plasma membrane Сa(2+),Mg(2+)-АТРase by сalixarene sulfonylamidines. Structure-activity relationship

Abstract

Previously we have already shown that tetrasulfonylamidinecalixarene C-90 inhibited plasma membrane Са2+,Mg2+-АТРаse of smooth muscle cells selectively to other ATPases of plasma membrane. To inhance the inhibitory effect of calixarenes several alkoxycalixarene sulfonylamidines structurally similar to calixa­rene C-90 were synthesized and their effects on the mentioned enzyme activity, the level of cytoplasmic Ca2+ concentration and hydrodynamic diameter of isolated smooth muscle cells were checked. It was shown that sulfonylamidino groups are crucial for Са2+,Mg2+-АТРаse inhibition, the efficiency of inhibition depends on their quantity and spatial orientation at the upper rim of calixarene macrocycle. Introduction of phenyl or tert-butyl groups into the upper rim and of long alkyl chains into the lower rim led to only slightl increase of inhibition efficiency. The inhibitory effect of studied calixarenes on Са2+,Mg2+-АТРаse correlated with effects on cytosolic Ca2+ concentration and hydrodynamic diameter of smooth muscle cells. The obtained results are important for creation of more effective and selective inhibitors of plasma membrane Са2+,Mg2+-АТРаse as regulators of smooth muscle contractility. Keywords: calixa­rene sulfonylamidines, intracellular Ca(2+) concentration, plasma membrane Са(2+);Mg(2+)-АТРаse, smooth muscle