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Vol. 42 No. 2, 2003
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 Hsieh1, Ying-Ru Chen2, Err-Lieh Hsu1 and Rong Kou2,*
1Department of Entomology, National Taiwan University, Taipei, Taiwan 106
2Institute of Zoology, Academia Sinica, Taipei, Taiwan 115
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.
Key words: Mythimna loreyi, Calcium channel antagonist, Corpora allata, Juvenile hormone acid, Intracellular calcium concentration.
*Correspondence: Tel: 886-2-27899541. Fax: 886-2-27858059. E-mail: kourong@gate.sinica.edu.tw
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