Abstract

In the rat heart the actin-bound nucleotide contained both ATP and ADP. The ratio of bound ATP to bound ADP depended on the functional state of the heart; it was higher in hearts stopped reversibly in diastole (low Ca(2+), high Mg(2+), or high K(+)), than in stimulated (inotropic agents or pacing) hearts. Immunoblotting and gel electrophoresis showed the existence of G-actin (30% of total actin) in the cytoplasm of the heart. Pure actin was isolated from rat hearts: in G-actin the bound nucleotide readily exchanged with ATP or ADP, and in F-actin the bound nucleotide did not exchange with ATP or ADP. The free and bound nucleotides were separated in the intact heart by extraction with 75% methanol at -15 degrees C. In rat hearts perfused with (32)P-labeled orthophosphate the actin-bound nucleotide rapidly exchanged with the cytoplasmic ATP. The full exchange of the bound ATP was immediate, whereas the full exchange of the bound ADP was slower. The full exchange of the bound ATP was independent of the heartbeat frequency, whereas the full exchange of the bound ADP was frequency dependent. The data suggest that the transformation of actin monomer-ATP to actin polymer-ADP is a part of the normal contraction-relaxation cycle of the rat heart.

Talk to us

Join us for a 30 min session where you can share your feedback and ask us any queries you have

Schedule a call

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.