To investigate the mechanism that the blood coagulation time in stressed fish decreases below normal level, relation between blood coagulation and thrombocyte was studied in carp
Cyprinus carpio (body weight: about 300g). Blood samples were collected from caudal vessels of unanesthetized fish with a syringe tipped with 20-gauge needle.
One m
l of the citrated blood was added with 0.1m
l of adrenaline (1, 10 and 100μM) or noradrenaline (0.3, 3.0 and 30μM) and incubated at 23°C for 10min. Ten and 100μM adrenaline decreased plasma recalcification time (PRT). Noradrenaline had less effect than adrenaline.
When 0.1m
l of the α-adrenergic receptor antagonist: phentolamine (0.1, 1.0, 10 and 100μM) or the β-adrenergic receptor antagonist: propranolol (0.1, 1.0, 10 and 100μM) were added to citrated blood before adding 10μM adrenaline, the effect of 10μM adrenaline was blocked by the phentolamine (1.0, 10 and 100μM) but not by the propranolol. TenμM adrenaline was effective to decrease PRT on thrombocyte-rich plasma, but not on thrombocyte-poor plasma and blood samples from stressed fish.
PRT decreased with the increase of thrombocyte number. Prothrombin time was not affected by these catecholamines.
These results suggest that thrombocyte participates in the intrinsic blood coagulation with the increase of its number and blood catecholamine level, particularly adrenaline, in the blood of stressed fish reacting to the adrenergic α-receptor.
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