Fate of Circulating Serotonin in the Hemolymph of the Crayfish, Orconectes limosus

Abstract

The fate of injected [¹⁴C]serotonin (0.1 μCi/1.6nmol per animal) was investigated in the crayfish Orconectes limosus after injection. Specific radioactivities reached highest values in the green gland, followed by intestine, gills, nervous tissue and digestive gland. Label accumulation was lowest in the tail muscle.

Cold serotonin injected into the hemolymph (50 nmol/100 g wet wt) was cleared with a mean half life of 12.9 +/- 2.6 min (15°C; N = 5). By HPLC separation of hemolymph samples taken at intervals after the injection of [¹⁴C]serotonin, the formation of a metabolic product could be demonstrated. The formation of the metabolite was not, however, detectable by native fluorescence, suggesting the metabolic breakdown of the indole ring. The combined amounts of acid soluble radioactivity recovered from hemolymph, green gland, digestive gland and intestine yielded 80-100%, 50-70% and 30-50% of the injected dose after 7 min, 1 h, and 4 h, respectively. Since other tissues did not account for the balance and less than 5% of the injected label had been excreted into the medium after 4 h the results suggest the gradual incorporation of the metabolites into the tissues