Determination of haemolymph protein in Manila clam (Ruditapes philippinarum) by Lowry's method

Haemolymph protein of Manila clam (Ruditapes philippinarum) was assayed with Lowry's method. Comparison was made between different approaches of coping with the interference by Mg²⁺ and Ca²⁺. The method of Bensadoun and Weinstein and double-precipitation of protein with 6-7.5% TCA were both effective. Incorporating interfering substances in the reagent blank and protein standards also helped to correct the interference. The absorbances of 0.3 M and 1.0 M NaOH-pretreated haemolymph samples were 1.7 ± 0.12 and 2.12 ± 0.20 (mean ± SD, N = 20) times higher than that without NaOH pretreatment. Pretreatment of protein standards (BSA) with NaOH did not have obvious effects on their absorbance.