Cardiovascular changes and physiological response during nitrite exposure in rainbow trout

• Published in: Journal of fish biology 2001-07, Vol.59 (1), p.13-27
• Main Authors: Aggergaard, S, Jensen, F B
• Format: Article
• Language: English
• Subjects: Oncorhynchus mykiss
• ISSN: 0022-1112; 1095-8649
• DOI: 10.1006/jfbi.2001.1590

Nitrite-exposed (1 m ) rainbow trout Oncorhynchus mykiss fell into two distinct groups with regard to susceptibility and physiological response. Group 1 accumulated nitrite in plasma to a concentration of 2.9 m within 24 h and died before 48 h. Group 2 survived for 96-144 h, and the accumulation of nitrite was slower, levelling off at a concentrationc . 2.3 m at 72 h. Methaemoglobin (metHb) formation was faster in group 1 than in group 2, but both groups had a metHb fraction c. 70% before dying. The extracellular electrolyte balance was perturbed significantly only in group 1, where plasma [Cl super(-)] decreased and plasma [K super(+)] increased. Heart rate increased rapidly, more in group 1 than in group 2. The tachycardia occurred before any significant changes in metHb or [K super(+)] had developed, suggesting that it was due to nitrite-induced vasodilation, possibly via nitric oxide generated from nitrite, that was countered by an increased cardiac pumping to re-establish blood pressure. Arterial blood pressure and pulse pressure were accordingly kept reasonably constant. Heart rate variability was significantly depressed in group 1. The ventilation rate was significantly increased fter 9 h of nitrite exposure in group 1, while the ventilation in group 2 did not increase significantly before 21 h. The data reveal that nitrite has substantial influence on the cardio-respiratory function in fishes. Copyright 2001 The Fisheries Society of the British Isles