Veterinary Biochemistry & Metabolism

In metabolic acidosis: 1. Decrease in pH and $[\text{HCO}_3^-]/[\text{H}_2\text{CO}_3]$ ratio occurs (C) $\rightarrow$ 2. Chemoreceptors trigger stimulation of the medullary respiratory center (E) $\rightarrow$ 3. Rapid deep breathing (hyperventilation) blows off $\text{CO}_2$ from extracellular fluid (A) $\rightarrow$ 4. Arterial $\text{pCO}_2$ decreases (D) $\rightarrow$ 5. The $[\text{HCO}_3^-]/[\text{H}_2\text{CO}_3]$ ratio and blood pH are restored towards normal 20:1 ratio (B). Sequence: (C), (E), (A), (D), (B).

Assertion (A) is true: antipyrine (and heavy water, deuterium oxide) is a standard indicator used to measure total body water (TBW). Reason (R) is false: antipyrine easily penetrates and distributes throughout both intracellular fluid (ICF) and extracellular fluid (ECF) because it is lipid-soluble (lipophilic), not hydrophilic. Hence, (A) is true but (R) is false.

In pulmonary capillaries (the Haldane effect), the alveolar environment features low $\text{pCO}_2$ (A) and higher $\text{pO}_2$ (B). Oxygen binding increases hemoglobin's affinity for oxygen (C) and displaces carbamino-bound $\text{CO}_2$ and protons. Low pH would favor $\text{CO}_2$ retention and $\text{O}_2$ release (the Bohr effect in tissues, not lungs). Thus, (A), (B) and (C) only.