Biologically active concentrations of potently vasoactive and platelet-active adenine nucleotides are generated in plasma by a variety of pathophysiological mechanisms. Although there is evidence that ATP and ADP are inactivated by endothelial ectonucleotidases, there has been little attempt to study the metabolic routes of their catabolism in blood or to assess the contribution of this process to their clearance in vivo. Therefore, we have studied the rates and patterns of catabolism of ATP, ADP, and AMP in whole blood, plasma, and isolated blood cells. Rates of degradation of each nucleotide in cell-free plasma ranged from 0.07-0.32 nmol/min/ml with 1 microM substrates to 1.1-3.6 nmol/min/ml with 100 microM substrates. The pattern of catabolism indicated that sequential dephosphorylation from ATP----ADP----AMP----adenosine occurs. In whole blood, the pattern was similar although ATP and ADP (but not AMP) breakdown was more rapid. This was due to leukocyte ectonucleotidase activity. The use of selective inhibitors demonstrated that catabolism was not due to nonspecific phosphatase activity and that plasma 5'-nucleotidase is distinct from ATPase or ADPase. In leukocytes, ATPase and ADPase activities were distinguishable, and each contributed substantially to the rates of catabolism in whole blood. Leukocyte 5'-nucleotidase did not measurably contribute to AMP dephosphorylation in blood. By comparison, ecto-ATPase and ecto-ADPase activities on cultured human umbilical vein endothelial cells were similar to those on leukocytes while endothelial 5'-nucleotidase per 10(6) cells was equivalent to the soluble activity in 1 ml of blood or plasma.(ABSTRACT TRUNCATED AT 250 WORDS)

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This study on human neutrophils was conducted to measure the kinetics of degranulation of the different cytoplasmic granules into phagocytic vacuoles, and to relate the timing of these events to the burst of respiration that accompanies phagocytosis by these cells . Purified neutrophils were incubated with latex particles opsonized with human immunoglobulin (Ig)G, and phagocytosis was stopped at timed intervals . The cells were examined by electron microscopy to document the sequence of degranulation of the cytoplasmic granules . The azurophil granules and lysosomes were identified by histochemical staining for peroxidase and acid phosphatase, respectively . Phagocytic vacuoles were separated from cell homogenates by floatation on sucrose gradients and assayed for contained lactoferrin, myeloperoxidase, and acid hydrolases. The conclusions drawn from the biochemical and morphological studies were in agreement and indicated : particle uptake and vacuole closure can be completed within 20 s ; both the specific and azurophil granules fuse with the phagocytic vacuole much earlier than is generally appreciated, with half-saturation times of 39 s (99% confidence limits, 15-72) ; oxygen consumption has kinetics similar to those of the fusion of these granules with the phagosome; degranulation of the acid hydrolases ,ß-glucuronidase, N-acetyl-ß-glucosaminidase (biochemical assays), and acid phosphatase (biochemical assay and electron microscopic cytochemistry) have kinetics of degranulation that are similar to each other but totally different from and much slower than that of myeloperoxidase with half-saturation times of between: 354 and 682 s (99% confidence limits, 246-883) . This suggests that the acid hydrolases are not colocated with myeloperoxidase in the azurophil granule but are contained in distinct lysosomes, or "tertiary granules."Phagocytosis by polymorphonuclear leukocytes is membrane which surrounds the engulfed particle, accomplished by an invagination of the plasma finally forming the limiting wall of the phagocytic J . CELL BIOLOGY

cells. Analysis of T cells infiltrating the lungs revealed only small increases in CD8؉ but not CD4 ؉ T-cell numbers in hdIVIg-treated mice. The mechanism of action of hdIVIg against tuberculosis in mice remains to be determined. Nevertheless, since hdIVIg is already widely used clinically, the magnitude and long duration of the therapeutic effect seen here suggest that IVIg, or components of it, may find ready application as an adjunct to therapy of human tuberculosis.

1. After decreasing muscle ATP by a 2 min period of intense exercise, we have studied purine metabolism by using high-pressure liquid chromatography. 2. A major increase in hypoxanthine concentration in plasma and urine was found with increases in xanthine and, in plasma, inosine. Erythrocyte hypoxanthine rose with the level in plasma, but there was no corresponding rise in IMP, the first intracellular metabolite of hypoxanthine. No rises in uridine or urate were found in plasma. 3. Plasma adenosine did not rise and fall significantly after exercise, but a small rise and fall in adenine nucleotide concentrations in plasma was found. 4. Running, swimming and games, which tended to be at the weekend, were associated with a rise in hypoxanthine and xanthine excretion; exercise was probably the cause of the higher excretion during the day than at night. Such activities do not produce changes in concentrations of ATP in muscle, although turnover must rise. 5. The results are consistent with widespread purine exchange between tissues and a 'circulating hypoxanthine pool'.