Presentation of an experimental method to induce in vitro ("organ chambers") respiratory acidosis and its effect on vascular reactivity

Abstract

PURPOSE:To create in vitro a model to generate acidosis by CO 2 bubbling "organ chambers", which would be useful for researchers that aim to study the effects of acid-base disturbs on the endothelium-dependent vascular reactivity. METHODS:Eighteen male Wistar rats (230-280g) were housed, before the experiments, under standard laboratory conditions (12h light/ dark cycle at 21°C), with free access to food and water. The protocol for promoting in vitro respiratory acidosis was carried out by bubbling increased concentrations of CO 2 . The target was to achieve an ideal way to decrease the pH gradually to a value of approximately 6.6.It was used, initially, a gas blender varying concentrations of the carbogenic mixture (95% O 2 + 5% CO 2 ) and pure CO 2 .RESULTS: 1) 100% CO 2 , pH variation very fast, pH minimum 6.0; 2) 90%CO 2 pH variation bit slower, pH minimum6.31; 3) 70%CO 2 , pH variation slower, pH minimum 6.32; 4) 50% CO 2 , pH variation slower, pH minimum 6:42; 5) 40 %CO 2 , Adequate record, pH minimum 6.61, and; 6) 30 %CO 2 could not reach values below pH minimum 7.03. Based on these data the gas mixture (O 2 60% + CO 2 40%) was adopted, CONCLUSION: This gas mixture (O 2 60% + CO 2 40%) was effective in inducing respiratory acidosis at a speed that made, possible the recording of isometric force.

Considerations about an experimental model of chronic metabolic acidosis in rats

“…Another study from our research group aimed to study the in vitro vascular responses induced by hypercapnic extracellular acidification (AH), as well as the endothelium-dependent mechanisms that are involved in the responses. It has been concluded that: 1) AH causes endothelium-dependent relaxation; 2) Indomethacin failed to block this relaxation, but the limitation of the method does not allow discarding some prostanoid paper; 3) Relaxation of the HA vessel is mediated via cGMP/NO and; 4) Hyperpolarization occurs by the action of the potassium channels SKCa, KATP, and Kv, without depending on BKCa channels (Nadai et al, 2014).…”

Efeito da acidose metabólica crônica sobre a reatividade da aorta torácica de ratos

“…Esses estudos adotaram modelo experimental in vivo e in vitro de distúrbios metabólicos e respiratórios e, os resultados tem permitido uma melhor compreensão sobre a influência do pH sobre a função vascular: 1) a acidificação extracelular induzida com HCl em aorta torácica de rato causou relaxamento dependente do pH nos anéis com endotélio intacto e anéis aórticos sem endotélio pré-contraídos com Phe; 2) a acidose metabólica in vitro induzida por borbulhamento de concentações aumentadas de CO 2 possibilitou o registro de forças isométricas; 3) a acidose metabólica aguda, in vivo, potencializa a resposta vasodilatadora da ACh e promove aumento nos níveis de NO. (Celotto et al 2011;Nadai et al 2014;Celotto et al 2016).…”