Farnesenic Acid Stimulation of Juvenile Hormone Biosynthesis as an Experimental Probe in Corpus Allatum Physiology

Abstract

Recent publications from our laboratories have indicated some experimental applications of short-term radiochemical procedures in vitro to the investigation of the temporal patterns of endocrine activity in the corpus allatum (CA) of adult female insects from two different species (Tobe and Pratt, 1975a; Weaver et al., 1975). These assays have relied upon the specific incorporation from the S-methyl group of (methyl-¹⁴C)-methionine into the methyl ester of known juvenile hormones, which lent itself to the estimation of rates of synthesis and release of C₁₆JH (JH III) by isolated glands incubated in defined tissue culture medium for 3 hr followed by chromatography and radiochemical quantitation. It has been previously reported that the addition of 2E,6E farnesenic acid to the incubation medium frequently stimulates the production of JH III by corpora allata (CA) from adult females of both Schistocerca gregaria and Periplaneta americana (Pratt and Tobe, 1974; Pratt and Weaver, 1974). It was proposed that farnesenic acid was esterified to methyl farnesoate and subsequently epoxidized at the 10,11 double bond to yield JH III (Pratt and Tobe, 1974). Detailed investigations with glands from S. gregaria showed that at optimal concentrations of farnesenic acid (20 μM), the rates of JH synthesis could be increased by up to 200-fold, and that these stimulated rates were constant over a 4 hr incubation period (Tobe and Pratt, 1974a).