Abstract
1. The K + -induced contracture consists of a phasic and a sustained component. Both were eliminated in Ca 2+ -free saline, but the sustained component recovered on the addition of Ca 2+ to the muscle. 2. Procaine mainly inhibited the phasic component. 3. Unlike the sustained component, the phasic component was inhibited by nifedipine in a concentration dependent manner. 4. Divalent cations such as Mn 2+ , Co 2+ and Ni 2+ markedly increased the sustained component at low concentrations, but decreased it at high concentrations. The cations also modified the phasic component differentially, but to a lesser extent. High concentration abolished the phasic component. 5. Ouabain markedly enhanced the sustained component. 6. Caffeine contracture was a phasic type. Its duration and amplitude were augmented by pre-soaking the muscle in Na + -reduced salines. Immediate pre-treatment with caffeine eliminated the phasic component of the 160mM K + -induced contracture. 7. These results suggest that a Na-Ca exchange mechanism may play a role in excitation-contraction coupling in insect muscle. Calcium ions flowing into the cell upon membrane depolarization may specifically activate the phasic component by way of a calcium-induced calcium releasing mechanism.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
More From: Comparative Biochemistry and Physiology Part C: Pharmacology, Toxicology and Endocrinology
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.