Abstract
The effects of ouabain 5 x 10-5 M, noradrenaline 10-7 M and nifedipine 100 mug/1 on the contractile force of the isolated rat left atrium were tested and compared at varying concentrations of calcium in the Ringer solution. The effect of ouabain was small, developed slowly and almost independently of the calcium concentration. Noradrenaline, which increases Ca++ influx during excitation, caused an increase in the contractile force which was complete within 2 min. The percentage as well as the absolute increase in contractile force was pronounced at lower, but small at higher calcium concentrations. Nifedipine, which reduces Ca++ influx during excitation, caused a decrease in contractile force which was complete within 2-4 min. The nifedipine-induced depression in contractile force decreased with a rise in the calcium concentration. It is assumed that the ouabain-induced increase in contractile force in the rat, is not mediated by an increase in the magnitude of the inward calcium current, and other modes of action for the inotropic effect of glycosides are discussed.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
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.