Elasmobranch pericardial function 2. The influence of pericardial pressure on cardiac stroke volume in horn sharks and blue sharks |
| |
| Authors: | D C Abel W R Lowell J B Graham R Shabetai |
| |
| Institution: | (1) Physiological Research Laboratory, A-004, Scripps Institution of Oceanography, University of California, 92093 San Diego, La Jolla, CA, USA;(2) Department of Medicine, University of California, San Diego;(3) Medical Service, Veterans Administration Medical Center, 92161 San Diego, CA, USA;(4) Present address: Marine Biomedical Research Program, Department of Anatomy and Cell Biology, Medical University of South Carolina, 171 Ashley Ave, 29425 Charleston, SC, USA |
| |
| Abstract: | The importance of negative pericardial pressure to heart function in clasmobranchs has been questioned due to the discovery of positive pericardial pressures in healthy horn sharks (Heterodontus francisci). We therefore implanted electromagnetic flow probes on the ventral aorta of horn sharks and blue sharks (Prionace glauca) and assessed stroke volume and pericardial pressure as pericardial fluid volume (PFV) was varied to test the hypothesis that elasmobranchs are capable of maintaining a relatively large stroke volume at pericardial pressures near and above ambient. Stroke volume was maximum between zero and 25% maximum PFV (maximum PFV: the volume of pericardial fluid required to open the pericardioperitoneal canal), where pericardial pressure was most negative. At 50% maximum PFV (pericardial pressure near or slightly above ambient) stroke volume was 70% and 98% of its maximum in horn sharks and blue sharks, respectively. At a larger PFV, stroke volume declined drastically, reaching zero where both PFV and pericardial pressure were maximum. Thus, at a pericardial pressure apparently associated with resting or mild activity, stroke volume is a relatively large proportion of the apparent maximum. Increased circulatory demands associated with strenuous activity may induce ejection of pericardial fluid through the perieardioperitoneal canal, which then lowers pericardial pressure. The lowered pericardial pressure causes an increase in stroke volume, indicating that control is in part effected by changing pericardial pressure. |
| |
| Keywords: | blue shark elasmobranch heart horn shark pericardioperitoneal canal pericardium pressurevolume stroke volume |
| 本文献已被 SpringerLink 等数据库收录！ |
|
