Zoological Studies

Pharmacological Effects of Calcium Channel Antagonists on Juvenile Hormone Acid Release and Intracellular Calcium Level in the Corpora Allata of Adult Male Mythimna loreyi (Lepidoptera: Noctuidae)

Yi-Chung Hsieh, Ying-Ru Chen, Err-Lieh Hsu and Rong Kou (2003) The pharmacological effects of calcium channel antagonists on the in vitro release of juvenile hormone acids (JHAs) and the intracellular calcium concentration ([Ca²⁺]_i ) in corpora allata (CA) of Mythimna loreyi adult males were investigated in this study. Newly dissected CA were first incubated in medium 199 for 1 h for equilibration, CA were then transferred to fresh medium containing Ca²⁺ channel antagonists for another 3-h incubation. Most antagonists of the voltage-dependent calcium channel (VDCC) subtypes ( L-, N-, P-, Q-, R-, and T-types), at physiological doses, were unable to inhibit JHA release, except for diazoxide. Among the non-specific calcium channel antagonists, cadmium (Cd²⁺), cobalt (Co²⁺), and lanthanum (La³⁺) were effective inhibitors of JHA release. The effects of VDCC antagonists (i.e., diazoxide and verapamil) and non-specific calcium channel antagonists on [Ca²⁺]_i were also measured in individual CA cells with Fura-2. Excised glands were first loaded with 20 µM fura-2/AM in lepidopteran saline for 45 min at 28°C in the dark. After hydrolysis, the [Ca²⁺]_i was observed for 30 min. Diazoxide (10-4 M) initially caused a significant depression of [Ca²⁺]_i , which then gradually increased to a normal level. Among the non-specific calcium channel antagonists, both Cd²⁺ and La³⁺ caused a significant depression of [Ca²⁺]_i . Our results suggest the possible existence of some kind of calcium channel in the plasma membrane of CA cells.