Induction of platelet activation by cobra venom factor from Naja naja atra in rat

AIM

To study the effects of cobra venom factor (CVF) on platelets of rat platelet rich plasma (PRP) and to elucidate its cellular mechanism.

METHODS

PRP was used to measure platelet aggregation and ATP-release simultaneously; prothrombinase, intracellular free calcium, and cAMP were assayed using chromogenic substrate, fluorophor Fura-2, and RIA respectively.

RESULTS

From 19.5 nmol.L-1 to 617 nmol.L-1 CVF induced platelet aggregation and ATP release concentration-dependently. The ATP release induced by CVF 195 nmol.L-1 was independent of aggregation and was much weaker than that induced by thrombin 1 U/ml. CVF 195 nmol.L-1 increased the prothrombinase activity on platelet surface in a time-dependent manner. SZ-1, SZ-21, and SZ-22, which are monoclonal antibodies against glycoproteins I b/IX, IIIa, and IIb located on platelet membranes, inhibited CVF-induced platelet aggregation. CVF 195 nmol.L-1 also elevated moderately intracellular free calcium ion from (141 +/- 46) to (240 +/- 64) nmol.L-1 in Fura-2 AM loaded platelets, and decreased intracellular cAMP.

CONCLUSION

Complement activator CVF induced platelet aggregation and ATP release, and increased prothrombinase activity on platelet surface. These actions were dependent on fibrinogen receptors on the platelet surface, elevation in intracellular free calcium ion, and reduction in cAMP.

Vertical transmission of human immunodeficiency virus type 1: frequency and correlation of transmission (review)

Child bearing age women constitute the fastest growing subset of the human immunodeficiency virus (HIV) infected population. Consistent with this fact is the increasing number of HIV infected children. Vertical transmission from mother to child is the most common route of infection. Because of the nature of the virus, it is difficult to determine the timing of infection. There are three time periods during which infection can occur: prenatally, perinatally, or postnatally. Evidence for each is presented within this review.