Intestinal alkaline phosphatase in patients with chronic renal failure.

Because of the suggestion that intestinal alkaline phosphatase was elevated in the serum of patients with chronic renal failure, we studied the serum of 42 patients undergoing hemodialysis with elevated enzyme activity. Using a sensitive and specific electroimmunoassay for the intestinal isoenzyme, 26 of 42 serum samples were positive, compared with 3 of 25 samples obtained from hospitalized patients with elevated phosphatase activity. The fractional amount of this isoenzyme was also higher, ranging from 1.5% to 41% of the total serum phosphatase, compared with 0.1%-1.2% in control sera. Kidneys removed during transplantation or postmortem contained a membranous phosphatase with immunologic activity identical to the intestinal isoenzyme in 5 of 6 patients. This enzyme accounted for 8%-21% of the total kidney phosphatase activity. By morphology the immunoreaction was localized to the apical membranes of the collecting tubules. Thus, the kidney is the likely source of the observed increase in serum intestinal-type phosphatase activity noted in patients with chronic renal failure. An elevation in the intestinal isoenzyme rather than the presence of early metabolic bone disease or hepatic disease should be considered in renal failure patients with mildly elevated (up to 50% over normal) total serum alkaline phosphatase.

Quantitation of human intestinal and liver/bone alkaline phosphatase in serum by rocket electroimmunoassay.

The separation and quantitation of the various human serum alkaline phosphatases has been largely by indirect and/or imprecise methods. A rocket electroimmunoassay method has been developed for the quantitation of the alkaline phosphatases, which uses enzymatic activity to detect the rocket and bromochloroindolylphosphate as substrate. The assay for intestinal phosphatase requires only one-dimensional electrophoresis, since the antibody to the intestinal enzyme does not cross-react with the other phosphatases. Both liver and bone enzymes give a line of identity when tested against antibody directed against the liver phosphatases, and these phosphatases require separation first by acrylamide gel electrophoresis before quantitation by crossed immunoelectrophoresis. Liver/bone enzyme levels in serum are easily detected within the linear range of the assay without concentration of the serum. The assay is 10-fold more sensitive than quantitation by acrylamide gel electrophoresis. The inability to detect circulating intestinal alkaline phosphatase in the serum of most fasting hospitalized patients has been documented by this sensitive assay, and the predominance of the liver isoenzyme has been confirmed. The assay should prove useful for determining the tissue of origin of serum alkaline phosphatases, and in providing quantitative data for physiological studies. It is not adaptable for automation and will not prove useful in the routine clinical laboratory.

Successful maintenance of suckling rat ileum in organ culture.

Ileum from rats 4, 9, 11, 12, and 15 days old can best be maintained for 24 hours in a system using Hanks' Balanced Salt Solution without fetal calf serum, at 25 degrees C and 21% O2. Suckling rat duodenum and jejunum were difficult to maintain well for 24 hours in this system or a variety of other systems that were tried. A temperature of 37 degrees C hastened deterioration of duodenum, jejunum or ileum. With ileum, 3H-thymidine and 14C-leucine were increasingly incorporated into DNA and protein over the 24-hour period. Light microscopy, as well as scanning and transmission electron microscopy, showed very good preservation of the ileum after 24 hours. The addition to the medium of hydrocortisone, 1 micron, and thyroxine, 0.01 micron, alone or in combination, did not change DNA or protein synthesis, or morphology, possibly because of the relatively short (24 hour) time period. Our organ culture system emphasizes the differences between suckling rat ileum and the rest of the intestine, and provides a new tool for evaluating, over a 24-hour period, the developing rat small intestine.