Effects of hydrogen sulphide on Ca2+ signalling in endothelial and smooth muscle cells

In the vascular system, ATP-sensitive K + -channels are a major target for H 2 S but recently evidence has accumulated that Na + - and Ca 2+ -permeable channels as well as intracellular Ca 2+ stores are also modulated by H 2 S. In this study we investigated the effect of H 2 S on Ca 2+ signalling on cultured endothelial and smooth muscle cells. Experiments were performed with endothelial cells isolated from porcine aorta (PAECs) and smooth muscle cells (SMCs) isolated from rat aorta and trachea. Activity of endothelial nitric oxide synthase (eNOS) was determined as conversion of incorporated L-[ 3 H]-arginine into L-[ 3 H]-citrulline. The intracellular free Ca 2+ concentration was measured with FURA-2. Incubation of PAECs with the H 2 S donors NaHS and GYY4137 markedly diminished both the release of Ca 2+ from intracellular stores and Ca 2+ entry elicited by receptor agonists such as ATP and histamine. As a consequence, the stimulatory effect of these agonists on NO formation was strongly diminished. In contrast to its inhibitory effect on ATP-induced Ca 2+ release and entry, H 2 S stimulated Ca 2+ influx from the extracellular space, but the resulting increase in intracellular free Ca 2+ concentration was not sufficient to affect endothelial NO formation. Inhibition of Ca 2+ release by H 2 S was not a peculiarity of endothelial cells but also occured in smooth muscle cells. Interestingly, similar to H 2 S, thiol-reducing agents such as DTT also inhibited ATP-induced store-operated Ca 2+ release in PAECs.