Pergamon 0022-1910(95)00011-9 J. Insect Physiol. Vol. 41, No. 8, 117-121, pp. 1995 Copyright 0 1995 Elsevier Science Ltd Printed in Great Britain. All rights reserved 0022-1910195 $9.50 + 0.00 Effects of ATP on the Interaction of Albumin and its C-terminal Amino Acid L-alanine with the “Sugar” Receptor Cell in Protophormia terraenovae (Diptera: Calliphoridae) A. LISCIA,*$ J. G. STOFFOLANO JR,? I. TOMASSINI BARBAROSSA,* P. MURONI,* R. CRNJAR* Received 4 May 1994; revised 28 November 1994 Stimulation with bovine serum albumin (BSA) and its C-terminal amino acid L-alanine evokes spike activity from the “sugar” cell of the labellar chemosensilla in Protophormiu. The presence of ATP in the BSA solution strongly enhances this effect, but is pH-dependent. On the contrary, addition of ATP to the L-alanine solution inhibits the “sugar” cell response regardless of pH. Reception mechanisms for BSA and L-alanine are discussed. Reception Blowflies ATP Albumin Amino acids INTRODUCTION In spite of the quantity and the importance of the investigations conducted on the effects of proteins and amino acids on taste chemosensilla in flies results are not conclusive (Wolbarsht and Hanson, 1967; Shiraishi and Kuwabara, 1970; Goldrich, 1973; Dethier, 1961, 1976; Gritsai, 1978; Shimada and Tanimura, 1981; Shimada et al., 1989; Barton Browne and Kerr, 1985). Recently, Liscia et al. (1995) found that BSA prevailingly stimu- lates the “sugar” receptor cell in Protophormia, in a similar way to that reported by Gritsai (1978) in Musca. In this respect, Becker and Peters (1989) reported that chemosensilla of the cockroach, Periplaneta americana, do not react with albumin, but respond to glc-bovine serum albumin, and this molecule stimulates the sugar receptor cells. As for the hypothesis that BSA stimu- latory effect is due to its terminal amino acids, Liscia et al. (1995) excluded the possibility of an interaction through the N-terminal amino acid (i.e. L-aspartic acid), while suggesting that BSA may exert its effect through its C-terminal amino acid L-alanine. In an attempt to ascertain whether BSA, L-alanine and sucrose interact with the same receptor site in the “sugar” cell and given the modulatory effect of adenosine nucleotides on the responses to salts and sugars (Liscia et al., 1987, *Dipartimento di Biologia Sperimentale, Sezione di Fisiologia Gen- erale, Universita di Cagliari, Viale Poetto 1, I-09126 Italy. tDepartment of Entomology, University of Massachusetts, Amherst, MA 01003, U.S.A. $To whom all correspondence should be addressed. 1989a. b), we analyzed the response to BSA and C-terminal amino acid with and without ATP in solution. MATERIALS AND METHODS its the Adult female blowflies, Protophormia terraenovae, (3-5 days old) were obtained from our colony main- tained under standard conditions. Experiments were made on the “largest” labellar chemosensilla (Wilczek, 1967). The tip-recording method of Hodgson et al. (1955) was used: the indifferent electrode (an Ag/AgCl wire) was inserted in the foramen magnum of an isolated head: the recording electrode was a glass micropipette filled with the test solution, which made contact with an Ag/AgCl wire connected to the input of the preamplifier (WPI 707). Records were displayed on a CR0 oscillo- scope (Tektronix 5100), recorded on magnetic tape and stored on floppy disks for later analysis. Identification of the different spike classes was achieved by means of the S.A.P.I.D. Tools spikes analysis software (Smith et al., 1990) following digitization with a Metrabyte DAS-16 A/D converter at 10,000 points/s for l-s period starting 30 ms after contact with the sensillum. Stimulating solutions The following two sets of solutions were tested: (1) 0.1 mM BSA, 0.1 mM BSA+ 1 mM ATP or 0.1 mM BSA + 1 mM ATP + 1 mM NaHCO,; (2) 1 mM L-alanine, 1 mM L-alanine + 1 mM ATP or 1 mM L-alanine + 1 mM ATP + 1 mM NaHCO,. Preliminary experiments 717