Platelet Aggregometry - Dose-related Responses to Arachidonic Acid in Childhood Nephrotic Syndrome

Camel platelet aggregation responses and the antiplatelet effect of camel urine: comparison between black and white camels

Human black and white-skinned races exhibited differences in platelet aggregation. However, no similar differences were described on white and black camels. This study aims to find out whether black and white camel skin color is associated with differences in camel platelet aggregation responses or the platelet inhibitory activity of their urine. Platelet aggregometry was undertaken in black and white camels, in response to adenosine diphosphate (ADP), Arachidonic acid (AA), Epinephrine (EPN), collagen, and Ristocetin. Platelet aggregometry was also done in human PRP after the addition of raw and serially diluted (1:2, 1:4 and 1:8) white and black camel urines. In black camels, platelet aggregation in response to ADP, AA, EPN and Collagen were slightly higher than in white camels. The addition of raw camel urine collected from mixed population of black and white camels to human platelets resulted in inhibition of platelet aggregation. Serial dilutions of camel urine (1:2, 1:4, 1:8) resulted initially in loss of the inhibitory action followed by enhancement of human platelet aggregation responses to ADP and AA. The neat and serially diluted white camel urines caused more inhibition of the human platelet aggregation responses than the black camel urines. This study uncovered a new biological feature in the camels. The camel skin color seems to be associated with different platelet aggregation responses as well as different antiplatelet activity of the camel urine; white camel urine was found to cause more platelet inhibition than black camel urine.

Characterization of the aggregation responses of camel platelets

BACKGROUND

Despite evidence of active hemostasis, camel platelets barely respond to common aggregating agents at standard doses used for human platelet aggregation.

OBJECTIVES

The purpose of the study was to find out whether camel platelets can be activated by high doses or combinations of aggregation agonists, and to characterize the receptor that mediates the aggregation response to adenosine diphosphate (ADP), the most potent agonist for camel platelets known so far.

METHODS

Aggregation studies were performed with platelet-rich plasma (PRP) in response to multiple doses or combinations of ADP, epinephrine (EPN), collagen, and arachidonic acid (AA). Aggregation responses to ADP were performed before and after the addition of the ADP receptor (P2Y12) antagonist Clopidogrel.

RESULTS

Camel platelets responded to ADP at doses higher than the standard dose for human platelets, and to combinations of EPN and other agonists, while no aggregation was elicited with EPN or AA alone. Clopidogrel blocked the ADP-induced aggregation responses in a dose-dependent fashion in vitro.

CONCLUSIONS

Camel platelet aggregation can be activated by increasing the dose of some agonists such as ADP, but not AA or EPN. Irreversible aggregation of camel platelets could also be triggered by a combination of EPN and ADP, and collagen and AA. Inhibition with clopidogrel suggests that camel platelets express the ADP receptor, P2Y12. Understanding platelet function in camels will add to the understanding of platelet function in health and disease.

Plasma albumin and platelet function: relevance to atherogenesis and thrombosis

Two papers published in this journal(1,2) during the past year remind us that plasma albumin concentrations can influence platelet function. These publications, together with epidemiological evidence showing that low plasma concentrations of albumin predict mortality from cardiovascular disease(3,4) have prompted this review.

Tissue factor pathway inhibitor in childhood nephrotic syndrome

It is now recognised that the extrinsic tissue factor pathway is the main trigger to the coagulation system in vivo. Its main inhibitor, tissue factor pathway inhibitor (TFPI), has never been studied in childhood nephrotic syndrome. The aim of the study was to monitor the level of TFPI in childhood nephrotic syndrome. One hundred and thirty-nine nephrotic children were classified into the following groups: group 1 (n=25), in relapse and receiving no treatment; group 2 (n=37), in relapse but receiving steroid treatment; group 3 (n= 45), in early remission and on steroids; group 4 (n=24), in established remission and receiving no steroids; group 5 (n=8), steroid-resistant. The controls (n=84) were healthy and age-matched. There was significant elevation of total TFPI levels in groups 1 and 2 and 3; levels were comparable to those of the healthy controls in group 4. The highest levels of total TFPI were recorded in group 5. Like total TFPI, the levels of the free form of TFPI showed a statistically significant increase in groups 1, 2, 3 and 4, when compared with levels in healthy controls. The highest levels of free TFPI were recorded group 5. We concluded that the elevated levels of both the total and free TFPI in various phases of nephrotic syndrome add another natural anticoagulant mechanism, which will attenuate the hypercoagulability of childhood nephrotic syndrome.