Platelet aggregation and platelet function analyzer 100 (PFA-100) closure time in camels—a comparative study with humans

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.

ADP-induced platelet aggregation after addition of tramadol in vitro in fed and fasted horses plasma

Adenosine diphosphate (ADP)-induced platelet aggregation in fed and fasted horses after addition of tramadol hydrochloride was evaluated in vitro. On 10 horses citrated blood samples were collected 2h after feeding (fed animals) and 21 h after feeding (fasted animals). Final concentrations of ADP 1 and 0.5 μM, and tramadol hydrochloride (1, 15, 30, 45 and 60 min after the addition of tramadol) were used to determine the maximum degree and initial velocity of platelet aggregation. Repeated measures multifactor analysis of variance (MANOVA) was used to evaluate the effect of feeding/fasting condition, ADP concentration and addition of tramadol. Findings showed statistical differences (P≤0.05) on studied parameters after addition of tramadol to different ADP concentrations in fed and fasted horses. The clinical relevance of these results is that tramadol provides many advantages as a therapeutic option; in fact, it is an inexpensive and a relatively new analgesic in equine veterinary medicine. Further investigations would be appropriate to compare the effects of different opioids but also using different concentrations of tramadol associated with other drugs in order to have substances which can regulate the functional activity of the platelets and to extend the knowledges on equine platelet aggregation.

Effects of hydrocortisone and aminophylline on the aggregation of equine platelets in vitro

The purpose of this study was to evaluate in vitro the effects of hydrocortisone and aminophylline on adenosine diphosphate (ADP)-induced platelet aggregation in horses. Blood samples from 30 healthy Thoroughbred horses were collected by via jugular venipuncture to assess platelet aggregation. Platelet-rich and platelet-poor plasma were prepared from all samples by centrifugation and divided into three different aliquots. In the first aliquot, platelet aggregation was measured after platelet activation with 1 µM and 0.5 µM ADP (Group A). In the other two aliquots, the effect of a 10 min preincubation with hydrocortisone (Group B) or aminophylline (Group C) on ADP-induced aggregation at final ADP concentrations of 1 µM and 0.5 µM was observed. Platelet aggregation, recorded by an aggregometer, was evaluated by measuring the maximum degree of platelet aggregation and the initial velocities of platelet aggregation were obtained. Our results demonstrated the inhibitory effect of hydrocortisone and the induction effect of aminophylline on equine platelet responses in vitro.

The antiplatelet activity of camel urine

BACKGROUND

For centuries, camel urine has been used for medicinal purposes and anecdotally proclaimed as a cure for a wide range of diseases. However, the apparent therapeutic actions of camel urine have yet to be subjected to rigorous scientific scrutiny. Recent preliminary studies from the authors' laboratory have indicated that camel urine possesses potent antiplatelet activity, not found in human or bovine urines, suggesting a possible role for camel urine in inhibiting platelet function. The goal of the current study was to characterize the antiplatelet activity of camel urine against normal human platelets based on agonist-induced aggregation and platelet function analyzer (PFA-100) closure time.

MATERIALS AND METHODS

Urine was collected from healthy virgin, pregnant, and lactating camels aged 2-10 years. Platelet-rich plasma (PRP) was prepared from blood collected from healthy individuals' blood into citrated anticoagulant. Agonist-induced aggregometry using donor PRP and PFA-100 closure times in whole blood were carried out in the presence and absence of added camel urine. The responses of platelets to multiple doses of camel urine were also assessed. The experimental procedure was repeated in human and bovine urines.

RESULTS

Camel urine completely inhibited arachidonic acid (AA) and adnosine diphosphate (ADP)-induced aggregation of human platelets in a dose-dependent manner. PFA-100 closure time using human whole blood was prolonged following the addition of camel urine in a dose-dependent manner. Virgin camel urine was less effective in inhibiting ADP-induced aggregation as compared to urine from lactating and pregnant camels; however, all three showed comparable inhibitory activity. Neither human nor bovine urine exhibited antiplatelet activity.

CONCLUSIONS

Camel urine has potent antiplatelet activity against ADP-induced (clopidogrel-like) and AA-induced (aspirin-like) platelet aggregation; neither human nor bovine urine exhibited such properties. These novel results provide the first scientific evidence of the mechanism of the presumed therapeutic properties of camel urine.

Protein expression in platelets from six species that differ in their open canalicular system

Platelets contain an invaginated, tubular membranous structure called the surface-connected open canalicular system (SCCS or OCS), which is contiguous with the plasma membrane and serves as a site for granule fusion and as a reservoir of membrane for platelet spreading. According to ultrastructural studies, platelets from some species lack OCS. In an attempt to correlate biochemical and functional attributes with the presence of an OCS, platelets from human, mouse and dog (OCS(+)), and from cow, camel and horse (OCS(-)) were analysed for differential protein expression and aggregation in response to thrombin. Among the 18 different cytoskeletal and regulatory proteins examined, five (Rac1, RhoA, Ras, calmodulin and Src) were expressed at higher levels in OCS(+) platelets (p < 0.05). Given the role of Arf6 in the formation of tubular invaginations in nucleated cells, the levels of Arf6-GTP were analysed in OCS(+) and OCS(-) platelets. There was no significant correlation between the presence of OCS and total Arf6 or Arf6-GTP levels. Comparison of platelet aggregation between different species suggests that OCS(-) platelets have delayed responses. This comparison of platelets from six different species, which differ in their OCS, shows the differential expression of known signaling components and foreshadows future studies focusing on OCS formation and function.

Haemostatic changes in laparoscopic cholecystectomy: a comparison between upper and lower limb measurements

BACKGROUND

The use of pnuemoperitonium to create the working environment for laproscopic cholecystectomy results in an increase in intraabdominal pressure, which exceeds the pressure of the venous-return from the legs. The resulting venous stasis may increase the risk of thrombosis formation and deep vein thrombosis in the lower limbs. However, there is no information as to whether the venous stasis will also exacerbate the coagulabililty of blood flowing out of the lower limbs.

AIM

The aim of the study is to find evidence of haemostatic activation in the blood draining the lower limbs, which experience venous stasis as a result of the laparoscopic cholecystectomy (LC) procedure.

MATERIALS AND METHODS

In this study, we prospectively studied 25 patients who underwent LC for uncomplicated cholelithiasis; 20 were female and 5 were male, aged between 17 to 65 years. LC was carried out according to a standard procedure. After general anesthesia, the patients were laid in a 30 degrees anti-Trendelenburg position, and pnuemoperitonium was maintained during the procedure with abdominal pressure of 12 mm Hg. The mean operating time was 55 minutes (range 25 to 118 min).Blood samples were collected simultaneously from the antecubetal fossa (the upper limb) and the dorsum of the foot (the lower limb), on 4 different occasions: i. preoperative; ii. after the induction of anesthesia, and before the inflation of the abdomen; iii. at the end of surgery, before deflation of the abdomen, and iv. 24 hours after surgery. LABORATORY ASSAYS: Prothrombin time, activated partial thromboplastin time, thrombin time, and plasma fibrinogen, Plasma Protein S (total and free), Protein C, Antithrombin, tissue plasminogen activator, and plasminogen activator inhibitor (PAI-I). Platelet function was assessed by the platelet function analyser (PFA100).

RESULTS

No significant differences were noted in all measured haemostatic parameters, including PFA100 closure times, when comparing the measurements that were taken simultaneously in the upper and lower limbs' blood. Plasma fibrinogen increased significantly 24 hours after surgery, and antithrombin levels dropped slightly, immediately after surgery, but recovered preoperative levels 24 hours after surgery. Coagulation inhibitors (total and free protein S and protein C), and fibrinolytic parameters did not show any significant fluctuations throughout the study intervals.

CONCLUSION

The finding of this study is of no significant activation of coagulation in the blood flowing out of the lower limbs at the time of venous stasis, adds to the criteria of safety of the current surgical procedure used in LC, including reverse Trendelenburg position and pneumoperitoneum that unavoidably produce significant stasis in the lower limbs.