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L M Greenbaum

Publications and source records attributed to L M Greenbaum.

61 records · Page 4Linked to original sources
PubMed1969

PMN-kinin and kinin metabolizing enzymes in normal and malignant leucocytes.

1. Studies have been carried out on the kinin-forming and kinin destroying activity of rabbit macrophages obtained from the lung before and after BCG injection and from the peritoneal cavity following mineral oil injection. A similar study was carried out with L-1210 leukaemic cells obtained from the peritoneal cavity of mice.2. The macrophages and leukaemic cells contain enzymes that form kinins from purified kininogen substrates at acid pH. The kinin-forming activity is not limited to the lysosomal fraction of the cell since it is found in extralysosomal compartments. Delta-guanidovaleryl benzyl ester partially inhibits the kinin-forming activity. Trasylol does not inhibit the kinin-forming activity of these cells, but does inhibit the kininases of these cells. The lack of effectiveness of this agent as a general anti-inflammatory agent is thus explained.3. The kininases of the normal and malignant cells are also inhibited by chloromethyl ketones such as tosyl-lysine chloromethyl ketone (TLCK) and tosyl-phenylalanine-chloromethyl ketone (TPCK) as well as by copper salts. Hydroxyquinoline has no inhibitory action on these cells, indicating that they differ from the plasma kininases.4. Investigation of the kinins produced by enzymes in rabbit and human polymorphonuclear (PMN) cells has demonstrated the formation of a kinin that differs from bradykinin and other known mammalian kinins in its pharmacological properties, molecular weight, and amino-terminal end group. This peptide has been named PMN-kinin.5. Overall, the investigation has demonstrated the importance of white cells in contributing to the formation and destruction of "extra-plasma" sources of kinins by enzymes which differ from plasma enzymes. Anti-inflammatory agents may have different actions on these cell enzymes from those on plasma enzymes.

Animals↗
PubMedDate not supplied

The effects of pathophysiologic state on the metabolism of vasoactive peptides by mammalian lung.

The pulmonary circulation plays a major role in the metabolism of angiotensin I (AI) and bradykinin through the activity of endothelial cell membrane-bound dipeptidylcarboxypeptidase, converting enzyme of kininase II. This report describes studies which investigate the effects of hypoxia on the function of converting enzyme in vivo in dogs and in endothelial cells in culture. Pulmonary converting enzyme function was assessed by both a blood pressure response technique and radioimmunoassay of bradykinin. Conversion of AI in vivo is decreased during acute alveolar hypoxia. At a PaO2 of 30 mmHg, conversion of AI is decreased to one-half control values. This decrease in AI conversion could not be related to hemodynamic factors in the pulmonary vasculature induced by hypoxia. Clearance of bradykinin by lung converting enzyme decreased from 96% at PaO2 levels above 95 torr to 0% below 26 torr. Hypoxic inhibition of enzyme activity was rapid in onset (less than 2 min), was closely correlated with PaO2 (r = 0.92, p less than 0.001) and reversible within 2 min after return to room air breathing. Converting enzyme activity of the systemic vascular bed also is inhibited by hypoxia. Converting enzyme activity also was studied by adding bradykinin or AI to endothelial cells in culture flasks and measuring residual peptide over time by radioimmunoassay. Hypoxia rapidly (less than 2 min) decreased enzyme activity and room air restored it rapidly. There was no enzyme activity below a PO2 of 30 mmHg. Hypoxia does not affect the activity of purified converting enzyme free of the endothelial cell. Metabolic and respiratory acidosis, as well as metabolic and respiratory alkalosis, had no significant effect on converting enzyme function in vivo in intact animals. While converting enzyme is resistant to a number of pathophysiological insults, it is extraordinarily responsive to acute hypoxia which may have important implications for systemic vasomotor control in conditions associated with clinical hypoxia and hypoxemia.

Acid-Base Equilibrium↗