Tyrosine and phenylalanine concentrations in haemolymph and tissues of the American cockroach, Periplaneta americana, during metamorphosis

Phenylalanine and tyrosine concentrations were measured in the haemolymph, fat body, and abdominal integument of the American cockroach, Periplaneta americana, during the pre- and post-ecdysial periods of cuticle formation and sclerotization.Gas-liquid chromatography of trimethylsilyl derivatives of phenylalanine, tyrosine, and their metabolites provided a very sensitive and rapid method for determining those amino acids in small haemolymph and tissue samples.Haemolymph tyrosine increased in two stages: initially near apolysis and 16 to 25 hr pre-ecdysis, reaching its highest concentration at ecdysis (3·5 μg tyrosine/mg haemolymph). During that time, total haemolymph tyrosine increased by approximately 700 μg/insect. Fat body and abdominal integument began to accumulate tyrosine near apolysis. Fat body tyrosine peaked between ecdysis and 3·3 hr post-ecdysis whereas abdominal integument tyrosine peaked at ecdysis. Maximum concentrations were 6·0 μg and 4·1 μg tyrosine/mg wet wt. of tissue, respectively. Between ecdysis and 24 hr post-ecdysis, the period of maximum sclerotization, total tyrosine in haemolymph and fat body decreased by approximately 600 μg and 420 μg/insect, respectively. Phenylalanine concentrations did not change significantly in the haemolymph, fat body, or abdominal integument during the pre- and post-ecdysial periods.The cockroach apparently does not store free phenylalanine or tyrosine in the fat body during larval development as compared to tyrosine storage in some Diptera. The rapid increase of haemolymph, fat body, and integument tyrosine just prior to ecdysis suggests another form of storage for this important amino acid.