Cardiac preload and venous return in swimming sea bass (Dicentrarchus labraxL.)

Abstract

SUMMARY Cardiac preload (central venous pressure, Pcv), mean circulatory filling pressure (MCFP), dorsal aortic blood pressure(Pda) and relative cardiac output(Q̇) were measured in sea bass(Dicentrarchus labrax) at rest and while swimming at 1 and 2 BL s-1. MCFP, an index of venous capacitance and the upstream venous pressure driving the return of venous blood to the heart, was measured as the plateau in Pcv during ventral aortic occlusion. Compared with resting values, swimming at 1 and 2 BLs-1 increased Q̇ (by 15±1.5 and 38±6.5%, respectively), Pcv (from 0.11±0.01 kPa to 0.12±0.01 and 0.16±0.02 kPa,respectively), MCFP (from 0.27±0.02 kPa to 0.31±0.02 and 0.40±0.04 kPa, respectively) and the calculated pressure gradient for venous return (ΔPv, from 0.16±0.01 kPa to 0.18±0.02 and 0.24±0.02 kPa, respectively), but not Pda. In spite of an increased preload, the increase in Q̇ was exclusively mediated by an increased heart rate (fh, from 80±4 beats min-1 to 88±4 and 103±3 beats min-1,respectively), and stroke volume (Vs) remained unchanged. Prazosin treatment (1 mg kg-1Mb) abolished pressure and flow changes during swimming at 1 BL s-1, but not 2 BL s-1, indicating that other control systems besides an α-adrenoceptor control are involved. This study is the first to address the control of venous capacitance in swimming fish. It questions the generality that increased Q̇ during swimming is regulated primarily through Vs and shows that an increased cardiac filling pressure does not necessarily lead to an increased Vs in fish, but may instead compensate for a reduced cardiac filling time.

Autoregulation of cardiac output is overcome by adrenergic stimulation in the anaconda heart

“…Pertinent to our study, whilst noradrenaline increased cardiac output, it decreased preload pressure. This contrasts with the in vivo situation, wherein alpha-adrenoceptormediated venoconstriction increases central venous pressure and promotes filling of the heart in snakes (Skals et al, 2006) and other vertebrates (Sandblom et al, 2005). Whilst stroke volume was maintained by noradrenaline under steady-state conditions, at a given preload pressure it was increased.…”

“…In most vertebrates, with the exception of some fish (Farrell, 1991), periods of heightened activity are accompanied by increased heart rate, whilst stroke volume changes only modestly (Bevegård and Shepherd, 1967;Secor et al, 2000;Sandblom et al, 2005).…”

“…Sandblom et al, 2005;Skals et al, 2005Skals et al, , 2006Enok et al, 2016). By mobilizing blood from the veins, preload pressure may be maintained, or even increased, despite the increased heart rate during activity (Sandblom et al, 2005;Skals et al, 2006).…”

Growth and hematology of pacu subjected to sustained swimming and fed different protein levels

“…These adaptions result in faster growth, better feed conversion ratios, increased survival rates, and decreased aggressive behavior (Moraes et al, 2009;Hackbarth, 2010). Sustained swimming also acts on blood flow, blood capillary diameter, and heart beating frequency (Sandblom et al, 2005).…”

Intermittent sustained swimming in 'matrinxã' Brycon amazonicus (Bryconidae: Bryconinae): hematological and metabolic responses

“…As fish is submitted to sustained swimming under moderate intensities some useful metabolic changes have been observed such as a shift of protein to lipid and carbohydrate catabolism to fill usual energetic demands (Moyes & West, 1995;Davison, 1997;Wood, 2001;Richards et al, 2002;Hackbarth & Moraes, 2006;Moraes et al, 2009). In addition, sustained swimming may result in changes of hemodynamic parameters such as blood flow, blood capillar diameter and beating frequency (Sandblom et al, 2005;Dunmall & Schreer, 2003;Altimiras & Larsen, 2000). However, the authors do not know upon any experimental assay with intermittent sustained swimming (ISS) in fish.…”