Synergistic activation of salmon cardiac function by endothelin and β-adrenergic stimulation

Abstract

The aim was to find out the effects of endothelin-1 (ET-1) in salmon (Salmo salar) cardiac contractile and endocrine function and its possible interaction with beta-adrenergic regulation. We found that ET-1 has a positive inotropic effect in salmon heart. ET-1 (30 nM) increased the contraction amplitude 17+/-4.7% compared with the basal level. beta-Adrenergic activation (isoprenaline, 100 nM) increased contraction amplitude 30+/-13.1%, but it did not affect the contractile response to ET-1. ET-1 (10 nM) stimulated the secretion of salmon cardiac natriuretic peptide (sCP) from isolated salmon ventricle (3.3+/-0.14-fold compared with control) but did not have any effect on ventricular sCP mRNA. Isoprenaline alone (0.1-1,000 nM) did not stimulate sCP release, but ET-1 (10 nM) together with isoprenaline (0.1 nM) caused a significantly greater increase of sCP release than ET-1 alone (5.4+/-0.07 vs. 3.3+/-0.14 times increase compared with control). The effects on the contractile and secretory function could be inhibited by a selective ETA-receptor antagonist BQ-610 (1 microM), whereas ETB-receptor blockage (by 100 nM BQ-788) enhanced the secretory response. Thus ET-1 is a phylogenetically conserved regulator of cardiac function, which has synergistic action with beta-adrenergic stimulation. The modulatory effects of ET-1 may therefore be especially important in situations with high beta-adrenergic tone.

The effect of adrenaline on the temperature dependency of cardiac action potentials in pink salmon Oncorhynchus gorbuscha

“…Therefore, frequency effects on APD tend to offset AD effects in ventricular tissue, an interaction that was not resolved in the present study. In addition, AD reduced the length of myocardial contraction in Atlantic salmon Salmo salar L. 1758 (Vierimaa et al , 2006), but a chronotropic effect of AD was absent and an inotropic effect was small for sea bass Dicentrarchus labrax (L. 1758) (Farrell et al , 2007) and two icefish species Chaenocephalus aceratus (Lönnberg 1906) and Notothenia coriiceps Richardson 1844 (Skov et al , 2008). Thus, the wide diversity of cardiac adrenergic response among fishes suggests that it may be an important target for natural selection, especially with respect to temperature challenges.…”