Inhibitory activity of the peptides derived from buffalo prolactin on angiogenesis.

The peptide fragments obtained by cathepsin digestion of purified buffalo prolactin (buPRL) monomer have been characterized using SDS-PAGE and FPLC with regard to size and pI. Their antiangiogenic activity was tested in chick embryo chorioallantoic membrane (CAM) assay and the human endothelial cells wound healing assay. Antiangiogenic activity was observed in cathepsin-cleaved fragments from buPRL. Further, a peptide sequence 45A- 46Q-47G-48K-49G-50F-51I-52T-53M-54A-55L-56N-57S-58C, which matched with human somatostatin (hSST), a known antiangiogenic factor, was located in the second loop between the first and second α-helices in the threedimensional structure of buPRL, obtained by homology modelling. The synthetic peptide matching with SST sequence was found to exhibit antiangiogenic activity in both in vitro and ex vivo assays. It was also observed that all the peptides related to buPRL could antagonize the vascular endothelial growth factor (VEGF) and bradykinin (BK)- dependent production of endothelial nitric oxide (NO), which is a pre-requisite for endothelial tube formation. It is concluded therefore that an internal sequence in buPRL and peptide fragments derived from cathepsin-digested buPRL exhibit antiangiogenic activities.

Production of antibodies specific to human chorionic gonadotropin in mice immunized against its chemical analogs.

Mice immunized against DS5-hCG-β and DS6-hCG-β, chemical analogs of β- subunit of human choriogonadotropin (hCG-β) in which 5 and 6 disulphide bonds respectively were reduced and alkylated, were found to produce antibodies specific to hCG without significant crossreactivity with human lutropin (hLH) as tested in a radioimmunoassay. In contrast, mice immunized against the native hCG-β subunit produced hLH crossreacting antibodies. While the anti-DS5, DS6-hCG-β serum was capable of selectively blocking the binding of [125I]-hCG to rat testicular LH/hCG receptors, it failed to inhibit the binding of [125I]-hLH to the same receptors. The radioimmunoassay for hCG using the mouse anti-DS5, DS6-hCG-β serum was not as sensitive as that employing rabbit anti- DS5, DS6-hCG-β serum. The minimal detection limit was 5 ng/ml for the mouse antibody as compared to 1 ng/ml for the rabbit antibody.