Does ammonia trigger hyperventilation in the elasmobranch, Squalus acanthias suckleyi?

Abstract

We examined the ventilatory response of the spiny dogfish, to elevated internal or environmental ammonia. Sharks were injected via arterial catheters with ammonia solutions or their Na salt equivalents sufficient to increase plasma total ammonia concentration [TAmm]a by 3-5 fold from 145±21μM to 447±150μM using NH4HCO3 and a maximum of 766±100μM using (NH4)2SO4. (NH4)2SO4 caused a small increase in ventilation frequency (+14%) and a large increase in amplitude (+69%), while Na2SO4 did not. However, CO2 partial pressure (PaCO2) also increased and arterial pHa and plasma bicarbonate concentration ([HCO3(-)]a) decreased. NH4HCO3 caused a smaller increase in plasma ammonia resulting in a smaller but significant, short lived increases in ventilation frequency (+6%) and amplitude (36%), together with a rise in PaCO2 and [HCO3(-)]a. Injection with NaHCO3 which increased pHa and [HCO3(-)]a did not change ventilation. Plasma ammonia concentration correlated significantly with ventilation amplitude, while ventilation frequency showed a (negative) correlation with pHa. Exposure to high environmental ammonia (1500μM NH4HCO3) did not induce changes in ventilation until plasma [TAmm]a increased and ventilation amplitude (but not frequency) increased in parallel. We conclude that internal ammonia stimulates ventilation in spiny dogfish, especially amplitude or stroke volume, while environmental ammonia only stimulates ventilation after ammonia diffuses into the bloodstream.

Ventilatory sensitivity to ammonia in the Pacific hagfish (Eptatretus stoutii), a representative of the oldest extant connection to the ancestral vertebrates

“…In our previous studies on responses to HEA in seawater fish, we had found that NH 4 HCO 3 was preferable to NH 4 Cl because, unlike the latter, it did not acidify the water (Wood and Nawata, 2011;Nawata et al, 2015;De Boeck and Wood, 2015). However, these studies had involved concentrations only up to 1.5 mmol l −1 , whereas in the present study we were using much higher concentrations, so we thought it prudent to investigate both salts.…”

Insights into the control and consequences of breathing adjustments in fishes-from larvae to adults

“…Owing to the limited data available on mechanisms of ammonia sensing, the following discussion focuses on the ventilatory effects of changes in environmental O 2 and CO 2 levels. However, readers interested in the ventilatory effects of the third respiratory gas, NH 3 , are directed to the following publications ( Zhang and Wood, 2009 ; Zhang et al, 2011 ; Zhang et al, 2013 ; De Boeck and Wood, 2015 ; Zhang et al, 2015 ; Eom et al, 2019 ; Eom et al, 2020 ; Eom and Wood, 2021 ; Porteus et al, 2021 ).…”

The sensing of respiratory gases in fish: Mechanisms and signalling pathways

“…At such times fish are known to hyperventilate to repay the O 2 deficit incurred during exercise or to offset the depressant effects of the post-prandial alkaline tide (Wood et al, 2005) on ventilation (Zhang et al, 2014). For these reasons and given the previously observed hyperventilatory effects of intra-arterial injection of NH 4 HCO 3 in trout (Mckenzie et al, 1993) and the known stimulatory effect of ammonia on central chemoreceptors in mammals (Wichser and Kazemi, 1974), Wood and colleagues in a series of papers tested the idea that ammonia is a specific ventilatory stimulant in rainbow trout (Zhang et al, 2014(Zhang et al, , 2013(Zhang et al, , 2011Zhang and Wood, 2009) and dogfish, Squalus acanthias (De Boeck and Wood, 2015). When taken together, the results of these studies provide compelling evidence that ammonia is a specific ventilatory stimulant in trout and dogfish likely via its combined interactions with peripheral (Zhang et al, 2011) and central (Zhang et al, 2013) chemoreceptors.…”