Abstract
Fish blood contains nucleated cells termed thrombocytes which are thought to be functionally analogous to mammalian platelets. The present study was undertaken to assess the aggregatory response of peripheral blood thrombocytes from the rainbow trout, Oncorhynchus mykiss. Incubation of Percoll density gradient purified thrombocytes with the thromboxane A2 mimetic, U-46619 (0.03-10 microM), alone or in the presence of human or trout fibrinogen, elicited a dose-dependent aggregatory response. A greater amount of aggregation was observed in the presence of fish, rather than human, fibrinogen (e.g. c 55% compared with 15% maximal aggregation respectively). This response was inhibited by pre-incubation of thrombocytes with the specific thromboxane A2 receptor antagonist, GR32191 (0.01-10 microM) with an IC50 value of 5.7 microM. Ultrastructural and aggregometry studies of thrombocyte aggregation at various time periods (1-12 min) after incubation with U-46619 (0.5 microM) revealed clear differences between the amount and dynamics of thrombocyte clumping in the presence of human, compared with trout, fibrinogen (final concentration 400 micrograms ml-1). Thrombocytes rapidly underwent shape change and aggregation after only 1 min incubation without the initial involvement of any other cell types. The maximum degree of aggregation was achieved after 4-8 min with larger aggregates formed in the presence of trout compared than human fibrinogen. Ultrastructurally, the thrombocytes in these aggregates displayed a number of changes compared with non-stimulated cells, including increased pseudopodial activity, a more pronounced canalicular system and condensation of the nuclear heterochromatin. After 12 min incubation the clumps of thrombocytes showed progressive disaggregatory behaviour, with some cells reverting back to their normal in vivo appearance. Neutrophilic granulocytes, present as contaminants in the thrombocyte suspensions, were occasionally found attached to the thrombocyte aggregates, perhaps suggesting a specific interaction similar to that occurring in mammals. Finally, and also of some significance, was the finding that trout thrombocytes exhibit phagocytic activity in vitro towards cell debris and contaminating bacteria, indicating that this cell type may possess both haemostatic and immunological capacities.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.