**Author details**

736 Lipoproteins – Role in Health and Diseases

involved is as much as 1 ng/ml HATKTAK.

as much as that from fresh platelets.

a high-affinity thrombin receptor on platelets [38-39]. Binding of thrombin with GP-1b

To confirm that LMW activator, HATKTAK, is produced by the platelets, we examined the LMW activator activity in the low-molecular-weight fractions of variously prepared platelet release products. We found that, in the platelet release products prepared using 4x105/l fresh platelets (0.1 unit/ml thrombin in the presence of 4 mEq/l Ca++), the LMW activator

By storage of the platelet-rich plasma, release of LMW activator from platelets induced by thrombin in the presence of Ca++ increased prominently. It was suggested that the concentration of LMW activator released from platelets stored for 120 hours is 10,000 times

One reason for the tremendous increase in LMW activator, HATKTAK, in the released products during storage is probably the loss of the precursor of MAPPs during storage, as shown in a previous report [26]. It is speculated that, in activated fresh platelets, LMW activator (HATKTAK) is produced as much as in stored platelets, but it decreases markedly because precursors of MAPPs remove it in fresh platelets. Another possible reason is that lipoproteins, apolipoproteins or fragments of apolipoproteins might be transported at high levels into platelets from the plasma during storage. In fact, it was shown that the concentrations of Apo CIII and Apo A1 in the platelet lysate increased markedly after storage of platelets in the form of platelet-rich plasma, but this was still too small to explain

Indirect ELISA of the platelet release products using anti-HATKTAK antibody was undertaken to prove the existence of HATKTAK. The results were satisfactory if synthesized pure peptides were used, and it was shown that the anti-HATKTAK rabbit antibody reacted positively to Apo CIII-derived peptides with C-terminal HATKTAK. However, we have not succeeded in establishment of a method to analyze HATKTAK in platelet release products. It is postulated that some substances derived from the platelet release products interfere with the adherence of HATKTAK on the wall of microtiter plate. Therefore, we examined the effect of the antibody on the LMW activator function. It was confirmed that the anti-HATKTAK antibody cancels the activity of the LMW activator in the platelet release products from fresh platelet-rich plasma and that stored for 120 hours. Mass spectrometry study revealed the presence of a substance corresponding to HATKTAK (m/z 756) in the platelet release products from platelets stored for 120 hours. Immunohistochemistry of the blood coagula revealed the existence of platelets with double-positive reaction to anti-HATKTAK and anti-CD61 antibodies. These findings strongly suggest that the LMW

A schematic illustration of the probable mechanism of production and release of MAPPs

At present, the mechanism of how MAPP contributes to neutrophilic phagocytosis enhancement after binding to neutrophils is not known. Because MAPPs possess transferrin molecules and anti-transferrin receptor antibody inhibits the action of MAPPs [28], it is

the observed increase in the effective dilution by as much as 1,000 times.

activator is HATKTAK and is produced and released by platelets.

and HATKTAK by platelets is depicted in Figure 9.

might enhance the trypsin-like activity of thrombin in platelets.

Haruhiko Sakamoto1,\*, Masaki Ueno1, Wu Bin1,2, Yumiko Nagai3, Kouichi Matsumoto1, Takao Yamanaka1,4 and Sumiko Tanaka1 *1Inflammation Pathology, Department of Pathology and Host Defense, Faculty of Medicine, Kagawa University, Kagawa, Japan 2Department of Gynecology and Obstetrics, Second Affiliated Hospital, China Medical University, San Hao Road, Shen Yan, China 3Division of Research Instrument and Equipment, Life Science Research Center, Institute of Research Promotion, Kagawa University, Kagawa, Japan 4Internal Medicine, Minami-Okayama Medical Center, Incorporated Administrative Agency National Hospital Organization, Okayama, Japan* 

<sup>\*</sup> Corresponding Author

### **Acknowledgement**

The authors wish to thank staff and students of the Faculty of Medicine, Kagawa University, for their cooperation in providing their blood for this study.

#### **5. References**


[13] Kirton CM, Nash GB (2000) Activated platelets adherent to an intact endothelial cell monolayer bind flowing neutrophils and enable them to transfer to the endothelial surface. J. lab. clin. med. 136: 303-313.

738 Lipoproteins – Role in Health and Diseases

The authors wish to thank staff and students of the Faculty of Medicine, Kagawa University,

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for their cooperation in providing their blood for this study.

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**Acknowledgement** 

enhancement of O2-

**5. References** 

147-158.

80: 1238-1246.

106: 391-399.

Nephron. 69: 248-252.



**Chapter 32** 
