Effects of endothelin-3 on the isolated guinea-pig ileum: role of Na+ ions and endothelin receptor subtypes

Endothelin (16–21): biphasic effect and no desensitization on the guinea‐pig isolated ileum

“…(2) The Na+-dependence of the effect of endothelin (16)(17)(18)(19)(20)(21) was similar to that observed for the cases of endothelin-1 (Miasiro & Paiva, 1990), endothelin-3 (Miasiro & Paiva, 1992) and sarafotoxins (unpublished data). However, repeated application of endothelin (16-21) did not induce desensitization of the preparation, in contrast to the desensitization induced by endothelin-I and endothelin-3, which was not reversed even after a 3 h resting period (Miasiro & Paiva, 1990;1992).…”

“…Isometric recordings showed that in low-Na+ (80 mM) medium both components of the response induced by endothelin (16-21) were greatly reduced (Figure 4) as was previously observed with endothelin-I (Figure 4; Miasiro & Paiva, 1990) and endothelin-3 (Miasiro & Paiva, 1992). Effect of endothelin (16-21) on tissues desensitized to endothelin-J and endothelin-3…”

“…By studying cross-tachyphylaxis between these two isopeptides, it was concluded that there are at least two subtypes of endothelin receptors in the guinea-pig ileum: one selective for endothelin-1 and another one which is non-selective (Miasiro & Paiva, 1992). To investigate whether or not the responses to endothelin (16-21) could interact with one of these receptor subtypes, we studied the possibility of cross-tachyphylaxis between endothelin-I or endothelin-3 and the hexapeptide.…”

“…We have investigated the effect of endothelin-1 (Miasiro & Paiva, 1990) and endothelin-3 (Miasiro & Paiva, 1992) on the guinea-pig ileum and observed that both peptides induced a direct biphasic effect (relaxation followed by contraction). In this tissue, the responses to endothelin-1 and endothelin-3 were characterized by a homologous desensitization (tachyphylaxis), and were markedly dependent on the Na+ gradient across the smooth muscle cell membrane (Miasiro & Paiva, 1990;1992).…”

Effects of endothelins on mechanical activity and inositol phosphate production in pregnant rat myometrium

“…In some strips, ET-3 at low concentrations produced a slight relaxation in our studies. Concerning this relaxant effect, Miasiro and Paiva [14] and Moritoki et al [15] demonstrated that ET-3 induced a relaxation followed by contraction in isolated guinea pig ileum and rat thoracic aorta, respectively. The mechanism of this relaxation is unknown.…”