PERFUSION-INDUCED CHANGES IN CARDIAC CONTRACTILITY DEPEND ON CAPILLARY PERFUSION

Citation
Ma. Dijkman et al., PERFUSION-INDUCED CHANGES IN CARDIAC CONTRACTILITY DEPEND ON CAPILLARY PERFUSION, American journal of physiology. Heart and circulatory physiology, 43(2), 1998, pp. 405-410
Citations number
14
Categorie Soggetti
Physiology
ISSN journal
03636135
Volume
43
Issue
2
Year of publication
1998
Pages
405 - 410
Database
ISI
SICI code
0363-6135(1998)43:2<405:PCICCD>2.0.ZU;2-E
Abstract
The perfusion-induced increase in cardiac contractility (Gregg phenome non) is especially found in heart preparations that lack adequate coro nary autoregulation and thus protection of changes in capillary pressu re. We determined in the isolated perfused papillary muscle of the rat whether cardiac muscle contractility is related to capillary perfusio n. Oxygen availability of this muscle is independent of internal perfu sion, and perfusion may be varied or even stopped without loss of func tion. Muscles contracted isometrically at 27 degrees C (n = 7). During the control state stepwise increases in perfusion pressure resulted i n all muscles in a significant increase in active tension. Muscle diam eter always increased with increased perfusion pressure, but muscle se gment length was unaffected. Capillary perfusion was then obstructed b y plastic microspheres (15 mu m). Flow, at a perfusion pressure of 66. 6 +/- 26.2 cmH(2)O, reduced from 17.6 +/- 5.4 mu l/min in the control state to 3.2 +/- 1.3 mu l/min after microspheres. Active tension devel oped by the muscle in the unperfused condition before microspheres and after microspheres did not differ significantly (-12.8 +/- 29.4% chan ge). After microspheres similar perfusion pressure steps as in control never resulted in an increase in active tension. Even at the two high est perfusion pressures (89.1 +/- 28.4 and 106.5 +/- 31.7 cmH(2)O) tha t were applied a significant decrease in active tension was found. We conclude that the Gregg phenomenon is related to capillary perfusion.