A low molecular weight antiplasmin of human blood platelets

SummaryHuman blood platelets are aggregated by the basic polymers polylysine and DEAE- dextran. Under certain conditions a second phase of aggregation, concomitant with the release reaction, is elicited. The presence of ADP, calcium ions and a plasmatic cofactor within the primary aggregates are necessary for the induction of the release reaction. These experiments demonstrate that cell contact per se does not lead to a release reaction ; in order to become effective it must take place in the presence of ADP.

Download Full-text

Chromatographic Isolation of the LDH-Isoenzymes of Human Blood Platelets and an Investigation of Their Enzyme Kinetics

Thrombosis and Haemostasis ◽

10.1055/s-0038-1651273 ◽

1968 ◽

Vol 20 (03/04) ◽

pp. 301-313 ◽

Cited By ~ 2

Author(s):

W Schneider ◽

K Schumacher ◽

B Thiede ◽

R Gross

Keyword(s):

Human Blood ◽

Blood Platelets ◽

Deae Cellulose ◽

Order Reaction ◽

Kinetic Properties ◽

Ldh Isoenzymes ◽

Kinetic Investigations ◽

Substrate Concentrations ◽

Chromatographic Isolation ◽

Human Blood Platelets

SummaryThe LDH-isoenzymes of human blood platelets show a distinct predominance of the isoenzymes 2 and 3 upon chromatography on DEAE-cellulose. Small amounts of LDH-1 are also present, while only traces of LDH-4 and -5 can be detected.Enzyme kinetic investigations of the principal isoenzymes LDH-1, -2 and -3 clearly show that the differences in inhibition constants with pyruvate as substrate which are demonstrable at 25° largely disappear at 37°. On the other hand, the differences among the isoenzymes in their affinity for pyruvate and lactate as substrate as well as in with respect to the optimal substrate concentrations of pyruvate are more marked at 37° than at 25°. Also, the type of inhibition found with lactate as substrate is increasingly the expression of a higher order reaction in going from LDH-1 to LDH-3. A dependence of the LDH distribution pattern upon the metabolism of the cell is discussed. A comparison of our results with thrombocytes with those of other workers with erythrocytes and leucocytes makes it unlikely that the LDH pattern is directly dependent upon the existence of an oxidative metabolism. Rather, the redox potential of the cell could be of importance for the nature of the pattern of isoenzymes and for their differing kinetic properties.

Download Full-text

Interaction of Vasopressin with Human Blood Platelets: Dependency on Mg2+

Thrombosis and Haemostasis ◽

10.1055/s-0038-1661662 ◽

1986 ◽

Vol 56 (03) ◽

pp. 260-262 ◽

Cited By ~ 6

Author(s):

Isabella Roos ◽

Fabrizia Ferracin ◽

Alfred Pletscher

Keyword(s):

Phosphatidic Acid ◽

Human Blood ◽

Arginine Vasopressin ◽

Specific Binding ◽

Blood Platelets ◽

Bivalent Cations ◽

Platelet Membranes ◽

Maximal Rise ◽

Human Blood Platelets ◽

Stimulation Of

SummaryArginine-vasopressin (AVP) in the presence of Mg2+ but not in the absence of bivalent cations led to accumulation of [32P]-phosphatidic acid ([32P]-PA) in human blood platelets. Mg2+ also enhanced the specific binding of [3H]-AVP to intact platelets. The concentrations of the cation which enabled AVP to cause half maximal rise of [32P]-PA and those inducing half maximal [3H]-AVP-binding were of the same order. It is concluded that the stimulation of phosphatidyl inositide breakdown by AVP in presence of Mg2+ is at least partially due to a Mg2+-induced enhancement of specific AVP-binding to the platelet membranes.

Download Full-text