Search

The influence of dioxane and ethanol on the rate of hydrolysis of p-nitrophenyl phosphate in the presence of an intestinal alcaline phosphatase can be interpreted as a dielectric constant effect, at high substrate concentration. The dielectric constant effect is a function of the pH of the medium and is maximum around pH 9.4 at 25 °C and pH 9.0 at 15 °C. An interpretation suggesting that the change in diameter of the enzyme molecule becoming an activated complex is minimum at a pH of maximum activity is proposed. The same model can take into account the influence of the ionic strength on the same reaction.

Changes induced in measurements of endogenous carbon monoxide (CO) production by blood in the lumen of the gut were studied in five normal volunteers. The study was undertaken because exogenous heme is absorbed by intestinal mucosal cells where the porphyrin ring is split with the release of CO that could contribute to blood CO levels and lead to a fallacious diagnosis of hemolytic disease. Volunteers who consumed 200 ml of their own blood doubled their endogenous production of CO (0.69 versus 0.34 µmoles/kg/hr). This suggested that at least 3% of the ingested heme was degraded and recovered as CO within 2 1/2 hr. Measurements of serum bilirubin also showed a significant increase after ingestion of blood. These data indicate that blood in the gastrointestinal tract can interfere with quantification of heme and bilirubin turnover from measurements of either endogenous CO production or bilirubin and suggest that this might occur with the ingestion of meat.

Changes induced in measurements of endogenous carbon monoxide (CO) production by blood in the lumen of the gut were studied in five normal volunteers. The study was undertaken because exogenous heme is absorbed by intestinal mucosal cells where the porphyrin ring is split with the release of CO that could contribute to blood CO levels and lead to a fallacious diagnosis of hemolytic disease. Volunteers who consumed 200 ml of their own blood doubled their endogenous production of CO (0.69 versus 0.34 mumoles/kg/hr). This suggested that at least 3% of the ingested heme was degraded and recovered as CO within 2 1/2 hr. Measurements of serum bilirubin also showed a significant increase after ingestion of blood. These data indicate that blood in the gastrointestinal tract can interfere with quantification of heme and bilirubin turnover from measurements of either endogenous CO production or bilirubin and suggest that this might occur with the ingestion of meat.

The life-span of the red blood cell (RBC) is difficult to estimate clinically, as hemolysis may exist in the presence of normal levels of hemoglobin and bilirubin, as well as normal reticulocyte counts. Clinically useful methods for quantification of the RBC life-span include isotope methods and measurement of endogenous carbon monoxide production. Chromium 51 is the isotope most widely used but has the disadvantage of requiring blood sampling for 30 days. Measurement of endogenous carbon monoxide production has the advantage of sensitivity to low-grade hemolysis and requires only three hours of the patient's time. It is potentially useful for demonstrating changing levels of hemolysis related to drug therapy or autoimmune states.(JAMA 230:1304-1305, 1974)

To the Editor.—Methyldopa is a widely used and effective antihypertensive agent. Although several side effects have been noted, emphasis has been on the ability of this drug to cause a positive direct Coombs reaction and, occasionally, hemolytic disease.1,2 The "lupus cell" phenomenom and clinical syndromes consistent with systemic lupus erythematosus have been reported.1,3 Less frequently reported is the association of methyldopa with hepatitis. This letter describes such a case.Report of a Case.—A 56-year-old white woman, seen in August 1970, complained of chest discomfort and blurred vision. Elevations of blood pressure had been noted in the past, but evaluation had failed to reveal a cause. The patient had a complex past history including a right radical mastectomy in 1944 for intraductal carcinoma, a left simple mastectomy in 1957 for fibrocystic disease, and a hemiglossectomy and right radical neck dissection for squamous cell carcinoma of the tongue