The kinetics of D3-3H metabolism in tropical sprue.

The metabolism of vitamin D3-3H was studied in a small group of controls and subjects with tropical sprue after the oral or intravenous administration of 8 to 10 microCi of D3-3H. The biological half life of D3-3H upon the administration of the isotope by the intravenous route was normal in 2 controls, very low in a subject with tropical sprue who had steatorrhea, and decreased in a subject with tropical sprue who did not present steatorrhea. After the administration of the isotope by the oral route, the biological half life was 35 hours in the control and no radioactivity could be detected in the plasma of the subject with tropical sprue who had steatorrhea. Twenty four hours after the intravenous dose the percentage of radioactivity in the plasma as HCC-3H was two times higher in the tropical sprue subjects than in the controls. When the dose was given orally the net absorption was 50.5% in the subject with tropical sprue and steatorrhea and 86.8% in the subject with tropical sprue who was partially treated. These results showed rapid clearance of the D3-3H in the subject with tropical sprue and steatorrhea indicating depletion of vitamin D stores in the tissues and decrease in the net absorption of the dose when given orally. The presence of a higher percentage of the dose in the plasma as HCC-3H after the intravenous and oral administrations in the tropical sprue subjects when compared to controls indicates that the diseased state does not alter vitamin D3 metabolism.

Factors responsible for weight loss in tropical sprue.

The respective roles of reduced dietary intake and malabsorption in the pathogenesis of weight loss in persons with chronic tropical sprue have been evaluated . Dietary intake was found to be significantly (P less than 0.001) less in a group of 45 patients with tropical sprue, all of whom had anorexia due to deficiency of folate and/or vitamin B12, than in a group of 51 healthy Puerto Ricans. Weight loss was equally prominent in those patients with tropical sprue who had normal absorption of fat and protein as in those who had excessive fecal loss and reduced absorption of these nutrients. Treatment of five sprue patients with folic acid or vitamin B12 for 2 weeks resulted in improved appetite and increased in dietary intake with weight gain in the absence of significant improvement in intestinal absorption. Treatment with oral tetracycline for a similar period of time in five other patients was not associated with vitamin repletion, return of appetite or weight gain. These observations indicate that reduced dietary intake resulting from anorexia caused by vitamin deficiency is a significant, and sometimes the most important, factor in the pathogenesis of weight loss in persons with chronic tropical sprue.

Jejunal perfusion of simple and conjugated folates in tropical sprue.

Absorption of labeled simple 3',5',9'-(3)H pteroylmonoglutamate, ([(3)H]PG-1) and conjugated pteroyl-mu[(14)C]glutamyl-gamma-hexaglutamate, ([(14)C]PG-7) folates was assessed in six patients with tropical sprue, before and after 6 mo of treatment, utilizing jejunal perfusion and urinary recovery techniques. Degradation products of [(14)C]PG-7 which were produced during perfusion were identified by DEAE-cellulose column chromatography. Jejunal mucosal activities of folate conjugase, lactase, sucrase, and maltase were measured in every patient. Malabsorption of both [(3)H]PG-1 and [(14)C]PG-7 was found in every untreated patient, with significant improvement after therapy. The urinary excretion of (3)H and (14)C paralleled the luminal disappearance of both isotopes. The chromatographic patterns of intraluminal degradation products of [(14)C]PG-7 obtained during perfusion did not differ from those previously found in normal subjects and were similar in studies performed before and after treatment. The activity of folate conjugase was increased in the mucosa of the untreated patients when compared to the post-treatment levels while the activities of mucosal lactase, sucrase, and maltase were originally low and increased significantly after therapy. These observations suggest that folate conjugase originates at a different mucosal locus than the brush border disaccharidases, and are consistent with previous evidence that folate conjugase is an intracellular enzyme. The present studies have demonstrated unequivocal malabsorption of both simple and conjugated folates in tropical sprue. In tropical sprue, folate malabsorption is the reflection of impaired folate transport and not of impaired hydrolysis.

Pteroylglutamic acid malabsorption in tropical sprue.

Pteroylglutamic acid (PGA) absorption was assessed in ten untreated tropical sprue (TS) and eight control subjects utilizing a marker perfusion technique. Physiologic concentrations of the vitamin (25 ng/ml) dissolved in iso-osmotic solutions containing either mannitol of glucose at a concentration of 55.6 mM were perfused on each subject on two consecutive days. A statistically significant difference in PGA absorption between TS and control subjects was obtained only when glucose was present in the perfusate. Thus, unequivocal malabsorption of PGA is demonstrable in all subjects with TS when more refined techniques than the ones applied heretofore are utilized.

Malabsorption of essential amino acids in tropical sprue.

The absorption of seven amino acids from an equimolar mixture containing each of the eight essential amino acids in a concentration of 20 mM was evaluated using a marker perfusion technique in 9 patients with untreated tropical sprue and in 6 healthy Puerto Rican control subjects. The rate of absorption of from two to six of the amino acids tested was lower in 7 of the patients than in the control subjects. The absorption of isoleucine, leucine, valine, and threonine was significantly lower in the group of sprue patients than in the control subjects. Treatment of 4 patients with oral tetracycline for 2 weeks was associated with return of amino acid absorption to normal in the 3 persons who had improved intestinal function, as tested by other parameters. More prolonged treatment was required for normalization of amino acid absorption in the 4th patient. These observations indicate that the absorption of certain essential amino acids is reduced in some patients with untreated tropical sprue.

Release of vitamin B12--binding protein by human leukocytes in vitro.

Human granulocytes (G) contain a vitamin B(12)-binding protein (B(12)BP). There is evidence that chronic myelogenous leukemia leukocytes (CMLL) may synthesize B(12)BP. Our prior studies suggested that intact, living intravascular G synthesize and release such protein into extracellular compartments in vivo. In the present study, CMLL were incubated in Trisbuffered Hank's basal salt solution (pH 7.2) containing 0.1% human serum albumin to study release of B(12)BP into the medium. B(12)BP was released continuously and in increasing amounts over a 5 hr period at 37 degrees C; this release was inhibited almost completely when the cells were incubated at 4 degrees C and by about half as much in the presence of N-ethylmaleimide (1 mmole/liter). Cycloheximide (50 mug/ml) had no effect on the release of B(12)BP but significantly inhibited incorporation of leucine-(3)H into leukocyte protein. G incubated with 20 mg/ml of compound 48/80, an experimental histamine-releasing agent, had a 6-fold increase in release of B(12)BP over a 2 hr period. Subcellular fractionation studies of human granulocytes demonstrate that most of the B(12)BP is associated with the granular (20,000 g) layer with an excellent correlation observed between its subcellular distribution and that of acid phosphatase.These findings suggest that the release of B(12)BP from G is mediated by an active process and provide further evidence that granulocytes are secretory as well as phagocytic cells.