Elasmobranch pericardial function. 1. Pericardial pressures are not always negative |
| |
| Authors: | Abel D C Graham J B Lowell W R Shabetai R |
| |
| Institution: | (1) Physiological Research Laboratory, A-004, Scripps Institution of Oceanography, University of California, 92093 San Diego, La Jolla, CA, U.S.A.;(2) Department of Medicine, University of California, San Diego;(3) Medical Service, Veterans Administration Medical Center, 92161 San Diego, CA, U.S.A.;(4) Present address: Department of Biology, College of Charleston, 29424 Charleston, SC |
| |
| Abstract: | Acute studies have led to the generalization that negative pericardial pressure is necessary for optimal cardiac function in elasmobranchs. We chronically instrumented horn sharks with pericardial catheters to test the hypothesis that ejection of pericardial fluid through the pericardioperitoneal canal (PPC) during routine handling could have accounted in part for previous measurements of exclusively negative pressures (–0.3 to –9.1 cm H2O) in elasmobranchs. Maximum and minimum pericardial pressures measured immediately following routine handling (acute pressures) were more negative than those measured in resting horn sharks at intervals from 1 to 27 days following handling (chronic pressures). Chronic pericardial pulse pressure was less than acute. Entirely positive pericardial pressures were observed on occasion. Handling of chronically catheterized horn sharks resulted in ejection of 21 per cent (range=10–26, n=5) of the initial pericardial fluid volume through the PPC and reduced pericardial pressure. Operating pericardial fluid volume of horn sharks averaged 2.0 ml.kg–1 (range=1.6–2.6, n=9). The PPC opened after 4.3±0.2 ml.kg–1 (x±S.E.) of elasmobranch saline had been slowly infused into the pericardium, corresponding to an average pressure of 1.3±0.2 cm H2O (n=10). The presence of the PPC plus a comparatively large pericardial fluid volume allows horn sharks to regulate pericardial pressure. Our analysis of pericardial pulse pressure, which can be an index of cardiac activity, suggests in contrast to previous studies that the elasmobranch heart can have relatively high stroke volumes at pericardial pressures near ambient. Thus, for venous return in resting or even moderately active elasmobranchs, it is more important that pericardial pressure be pulsatile than at a mean level which is negative. |
| |
| Keywords: | elasmobranch heart horn shark pericardioperitoneal canal pericardium pressure-volume |
| 本文献已被 SpringerLink 等数据库收录！ |
|
