Phosphate in Lobster Nerve. 20

Abstract

The nerves of the large claws and walking legs of the lobster {Homarus americanus) with or without the abdominal ganglion chain were carefully dissected into iced mortars. They were ground and analyzed, either at once or after standing for 1/2 to 3 hours in closed vessels in moist oxygen or nitrogen at 23-25°C. In a few cases companion analyses were run on nerves resting or stimulated in oxygen, stimulation being continued with fairly strong induction shocks at 100 per second for half an hour. The method of analysis was essentially that described by Fiske and Subbarow 1 , involving extraction with 10% iced trichloracetic acid, part of the filtrate being used to determine total acid-soluble phosphorus after ashing with sulphuric and nitric acids, the larger portion being neutralized and treated with calcium chloride-calcium hydroxide precipitant. After centrifuging and washing, the inorganic phosphate remained in the precipitate. Phosphagen was determined in the clear solution after reacidification with hydrochloric acid and standing at room temperature for 2 days, according to Meyerhof 2 . Phosphate was finally estimated in each fraction by the Fiske-Subbarow method, using a total volume of 15 cc. and comparing with a phosphate standard of 8.0 mg. % strength.

The rate of hydrolysis of the phosphagen compound, as tested with acid for different time intervals, clearly showed it to be of the arginine phosphate rather than the creatin phosphate type, which is in conformity with the difference in muscle phosphagens in vertebrates and crustaceans. The usual controls of the adequacy of separation and determination demonstrated the validity of our procedure.