Abstract
Saline (0.9% NaCl) is used in clinical and research settings as a vehicle for intravenous drug administration. While saline is a standard control in mouse studies, there are reports of hyperchloremic metabolic acidosis in high doses. It remains unknown if metabolic acidosis occurs in mice and/or if compensatory increases in breathing frequency and tidal volume accompany saline administration. It was hypothesized that saline administration alters blood pH and the pattern of breathing in conscious CD‐1 male mice exposed to air or hypoxia (10% O2, balanced N2). Unrestrained barometric plethysmography was used to quantify breathing frequency (breaths/min; bpm), tidal volume (VT; mL/breath/10 g body weight (BW)), and minute ventilation (VE; mL/min/10 g BW) in two designs: (1) 11‐week‐old mice with no saline exposure (n = 11) compared to mice with 7 days of 0.9% saline administration (intraperitoneal, i.p.; 10 mL/kg body mass; n = 6). and (2) 17‐week‐old mice tested before (PRE) and after 1 day (POST1, n = 6) or 7 days (POST7, n = 5) of saline (i.p.; 10 mL/kg body mass). There were no differences when comparing frequency, VT, or VE between groups for either design with room air or hypoxia exposures. Hypoxia increased frequency, VT, and VE compared to room air. Moreover, conscious blood sampling showed no differences in pH, pa CO 2, paO2, or HCO3− in mice without or with 7 days of saline. These findings reveal no differences in ventilation following 1 and/or 7 days of saline administration in mice. Therefore, the use of 0.9% saline as a control is supported for studies evaluating the control of breathing in mice.
Highlights
Saline (0.9% NaCl) is often implemented as a resuscitation solution and/or conduit for drug administration in the hospital and research setting (Takahara et al 1977; Gainetdinov et al 1999; Gaiardi et al 2001; Waters et al 2001; Hagiwara et al 2008)
Body weight was significantly different between CON and SAL groups at data acquisition (36.8 (1.7) vs. 31.8 (5.8) grams, respectively; P < 0.05), measures were normalized to 10 grams/body weight (10 g/BW) to account for differences in mass
The findings of this study suggest that there is no impact of 1 and/or 7 days of saline administration on patterns of breathing when mice are exposed to either room air or hypoxia
Summary
Saline (0.9% NaCl) is often implemented as a resuscitation solution and/or conduit for drug administration in the hospital and research setting (Takahara et al 1977; Gainetdinov et al 1999; Gaiardi et al 2001; Waters et al 2001; Hagiwara et al 2008). In addition to a treatment option for trauma and surgery patients, saline is used in research for drug delivery and as a vehicle control (Takahara et al 1977; Omigbodun et al 1991; Vezina et al 1999; Gaiardi et al 2001; Chien et al 2012). Physiological Reports published by Wiley Periodicals, Inc. on behalf of The Physiological Society and the American Physiological Society.
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