Bicarbonate overproduction

Human carbonic anhydrase II (HCAII) is present in the nonpigmented epithelial cells of the eye, where it catalyzes the reversible, zinc-assisted hydration of carbon dioxide to generate bicarbonate. Overproduction of bicarbonate results in increased intraocular pressure, which ultimately can produce optic nerve damage and blindness. Accordingly, HCAII inhibitors are used to treat diseases associated with high intraocular pressure, such as glaucoma, because they inhibit bicarbonate production and thereby decrease sodium and fluid secretion into the eye. 

Metabolic acidosis An acid-base disorder caused by overproduction or accumulation of acid (often lactic acid see lactic acidosis) or a deficit of base (i.e., bicarbonate). 

Several relatively common disorders result in aldosterone secretion abnormalities and aberrations of electrolyte status. In Addison s disease, the adrenal cortex is often destroyed through autoimmune processes. One of the effects is a lack of aldosterone secretion and decreased Na+ retention by the patient. In a typical Addison s disease patient, serum [Na+] and [CL] are 128 and 96 meq/L, respectively (see Table 16.2 for normal values). Potassium levels are elevated, 6 meq/L or higher, because the Na+ reabsorption system of the kidney, which is under aldosterone control, moves K+ into the urine just as it moves Na+ back into plasma. Thus, if more Na+ is excreted, more K+ is reabsorbed. Bicarbonate remains relatively normal. The opposite situation prevails in Cushing s disease, however, in which an overproduction of adrenocorticosteroids, especially cortisol, is present. Glucocorticoids have mild mineralocorticoid activities, but ACTH also increases aldosterone secretion. This may be caused by an oversecretion of ACTH by a tumor or by adrenal hyperplasia or tumors. Serum sodium in Cushing s disease is slightly elevated, [K+] is below normal (hypokalemia), and metabolic alkalosis is present. The patient is usually hypertensive. A more severe electrolyte abnormality is seen in Conn s syndrome or primary aldosteronism, usually caused by an adrenal tumor. Increased blood aldosterone levels result in the urinary loss of K+ and H+, retention of Na+ (hypernatremia), alkalosis, and profound hypertension. 

The reported pKi values range from 3.9 to 5.7 (21,48). For our considerations it is essential that the pK value of uric acid is lower than that of bicarbonate, the latter being 6.1. All acids with a pK value of less than 6.1 are able to release carbon dioxide from bicarbonate. Our gasometric measurements showed a slow but clear release of carbon dioxide after addition of uric acid to sodium bicarbonate. A prolonged overproduction of acids (even weak acids such as uric acid inevitably impairs the alkali reserve if this is not compensated for. 

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See also in sourсe #XX -- [ ]

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