Recent evidence suggests that endogenous hydrogen sulfide (HS) potentiates the smooth muscle relaxant effect of nitric oxide (NO) in mammals (Hosoki et al. 1997). Whether a similar mechanism exists in invertebrates is unknown. We tested the effects of SNP and HS in combination with acetylcholine (ACh) on the isometric contractile force of body wall circular muscle strips from the marine echiuran worm Urechis caupo. This animal is adapted to moderate HS concentrations, being regularly exposed to 50 μM HS in its natural environment. ACh (100 μM) consistently induced a transient contraction in body wall muscle strips, but application of HS (10-1000 μM) or SNP (10-1000 μM), either alone or in combination, immediately prior to ACh had no relaxant effect (p>0.5). In the absence of ACh, HS alone (100-1000 μM) stimulated a small contraction (half the force of ACh), while SNP alone had no effect. However, the simultaneous addition of 100 μM SNP with HS resulted in a five-fold increase in contraction force compared with that of HS alone (p<0.01), which was then only slightly increased (<50%) by the subsequent addition of ACh. These results indicate invertebrate muscle tissue is sensitive to HS, and that NO (as SNP) potentiates HS, although the concentrations required are higher than in mammals. Unlike mammalian smooth muscle, HS induces contraction of invertebrate muscle. This is particularly intriguing considering U. caupo contains abundant HS-binding molecules and HS-oxidation mechanisms for HS detoxification during HS exposure.
|Original language||English (US)|
|State||Published - Mar 20 1998|
All Science Journal Classification (ASJC) codes
- Molecular Biology