OPC-28326, a selective femoral vasodilator, is an alpha2C-adrenoceptor-selective antagonist.

OPC-28326 has been reported to selectively increase femoral blood flow in open-chest dogs and autoperfused canine femoral artery preparations. Preliminary data indicated that OPC-28326 has a high affinity at the alpha2-adrenoceptor. In the present study, we tested OPC-28326 in isoflurane anesthetized rats at a dose of 3 mg/kg of body weight, given intraduodenally. OPC-28326 significantly increased femoral blood flow, by 44.7 +/- 13.8%, 45 min after drug administration, whereas carotid blood flow increased by only 3.6 +/- 5.5% (n = 6). Chinese hamster ovary cell lines overexpressing rat alpha2D-, alpha2B-, or alpha2C-adrenoceptor were established. These cells also coexpress luciferase, driven by cAMP elevation. In radioligand binding assays using cell membrane preparations, OPC-28326 dose dependently competed with [3H]RX821002 binding, with calculated K(i) values of 3840 +/- 887, 633 +/- 46, and 13.7 +/- 1.9 nM on alpha2D-, alpha2B-, and alpha2C-adrenoceptor, respectively. A similar affinity and rank order of potency were also found for OPC-28326 on the alpha2-subtypes using epinephrine as agonist in luciferase assays. No agonistic effect of OPC-28326 was detected on any of the alpha2-adrenoceptors. Finally, in situ hybridization performed on skeletal muscle tissue sections collected from rat hind limb (musculus gastrocnemius) demonstrated a high level expression of alpha2C in the vascular tissues. Thus, the abundance of alpha2C in the skeletal muscle may account for the selective effect of OPC-28326 in increasing femoral blood flow.

Interaction between GPIbalpha and FcgammaIIA receptor in human platelets.

Glycoprotein (GP) Ib (alpha and beta) in platelets forms a noncovalent hetero-oligomeric complex with GPIX and GPV and serves as a receptor for von Willebrand factor (vWF), which mediates the initial adhesion of platelets to the subendothelium after vascular damage and also plays a role in thrombin-induced platelet activation. We investigated the interaction between GPIbalpha and FcgammaIIA receptor using a yeast two-hybrid system and mutagenesis, and we identified residues R542G543R544 in GPIbalpha and D298D299D300 in FcgammaIIA receptor as the primary interaction sites. These results further confirmed the interaction between GPIbalpha and FcgammaIIA receptor and support the hypothesis that the signal transduction of GPIb-IX-V that leads to platelet activation may be partially mediated through FcgammaIIA receptor.

An anti-platelet agent, OPC-29030, inhibits translocation of 12-lipoxygenase and 12-hydroxyeicosatetraenoic acid production in human platelets.

1. In human platelets, arachidonic acid is mainly metabolized by the two enzyme systems; cyclo-oxygenase and 12-lipoxygenase. Cyclo-oxygenase produces prostaglandin H(2) which is further converted to thromboxane B(2). 12-Lipoxygenase synthesizes 12(S)-hydroperoxyeicosatetraenoic acid which is reduced to 12(S)-hydroxyeicosatetraenoic acid (12(S)-HETE). 2. An anti-platelet compound, OPC-29030, dose-dependently inhibited 12(S)-HETE production with an IC(50) of 0.06+/-0.01 microM, but not synthesis of thromboxane B(2) in human platelets. Although the compound suppressed 12(S)-HETE production in human platelets, cytosolic 12-lipoxygenase activity was not inhibited up to 10 microM. Essentially identical data were obtained with a 12-lipoxygenase of human erythroleukaemia cells which had megakaryocyte/platelet-like properties. 3. OPC-29030 also suppressed production of 5(S)-HETE, a 5-lipoxygenase product, in rat basophilic leukaemia cells without inhibiting enzyme activity. It has been shown that 5-lipoxygenase binds to membrane 5-lipoxygenase-activating protein (FLAP) to produce 5(S)-HETE, and thus FLAP inhibitor suppresses cellular 5(S)-HETE production. 4. A FLAP inhibitor, L-655,238, suppressed platelet 12(S)-HETE production, but had no effect on the 12-lipoxygenase activity. 5. Western blot analysis showed that platelet 12-lipoxygenase translocated from cytosol to membranes upon thrombin stimulation, and OPC-29030 suppressed this process in a dose-dependent manner. 6. These results suggest that the 12-lipoxygenase of human platelets binds to FLAP or a similar protein, and OPC-29030 suppresses 12(S)-HETE production by inhibiting a certain step of the 12-lipoxygenase translocation.

Possible involvement of calpain in the growth of estrogen receptor positive breast cancer cells.

Calpain (Ca2(+)-activated neutral protease, EC 3.4.22.17) has been reported to hydrolyze the estrogen receptor (ER). However, there has been no report available regarding the role of calpain in the growth of breast cancer cells. To investigate the role of calpain in the growth of various breast cancer cell lines, we employed a synthetic peptide, calpeptin, which is a cell permeable specific inhibitor of calpain. Calpeptin inhibited the cell growth of ER positive breast cancer cells, such as MCF-7, T-47D, and ZR-75-1 in a dose dependent manner in the presence of E2. However, the growth of ER negative breast cancer cells, MDA-MB-231, was not inhibited by calpeptin. It is suggested that calpain plays an important role in the growth of ER positive breast cancer cells.

Phyllodes tumor in epileptics: a report of two cases.

Phyllodes tumor is an uncommon breast neoplasm characterized by a proliferation of both stromal and epithelial elements. In 1989, two young patients with phyllodes tumors were referred to our surgical department because of the detection of breast lumps. Interestingly, both patients also had epilepsy and had been taking anticonvulsants. An analytical case control study revealed that no significant difference between the control group and phyllodes group was found for various categories. In addition, no anticonvulsant medication had been prescribed in either the control group or the phyllodes group except for these two cases. We herein report two cases of phyllodes tumors occurring in two young epileptic patients.

The involvement of protein phosphatases in platelet activation.

Protein phosphatase (PP) activities have long been known in platelets, but their physiological roles in platelet reactions are not well understood. Since the discovery of the okadaic acid (OA) class of compounds, potent and cell-permeable PP 1/2A inhibitors, evidence for the active involvement of PP1/2A in platelet reactions has rapidly accumulated. This article reviews the possible involvement of PP1/2A in platelet function by focusing on the effects of OA class compounds on agonist-induced platelet reactions.

Revascularization of the occluded donor artery of a femorofemoral crossover by axillary bypass.

In patients over 70 years of age with disabling leg ischaemia, femorofemoral crossover bypass with an externally supported polytetrafluoroethylene (PTFE) graft is the treatment of choice for unilateral occlusion of the iliac artery. Over a 6-year period, 18 elderly patients underwent femorofemoral bypass, six of whom had received percutaneous transluminal angioplasty before surgery for stenosis of the contralateral external iliac artery (donor artery). Symptoms of ischaemia recurred in three patients because of deterioration of the donor iliac artery more than 2 years after surgery, although all three grafts were well visualized by angiography. Revascularization was attempted in these three patients by an axillary bypass. Disabling symptoms of ischaemia were completely relieved by this procedure, although two patients underwent reoperation 9 and 16 months after the axillary bypass respectively. All three patients are now free from symptoms of ischaemia. It is concluded that: deterioration of the donor iliac artery after femorofemoral bypass does occur, although it has been considered unlikely because of decreased peripheral resistance; in spite of complete occlusion of the donor artery, grafts remain patent, proving the excellent antithrombogenic activity of externally supported PTFE; and revascularization using additional axillary bypass is a feasible procedure in such cases.