title: Voltage-dependent calcium channels in the corpora allata of the adult male loreyi leafworm, Mythimna loreyi.
abstract: In the corpora allata (CA) of the adult male loreyi leafworm, Mythimna loreyi, juvenile hormone acid (JHA) biosynthesis and release show a dose dependence on extracellular Ca(2+) concentration. Maxima are obtained with Ca(2+) concentrations of 2-10 mM, and synthesis and release are significantly inhibited under a Ca(2+)-free condition. The Ca(2+)-free inhibition of JHA release can be reversed by returning the glands to medium at 5 mM Ca(2+). The cytosolic free Ca(2+) concentration ([Ca(2+)](i)), which was measured with fura-2, in individual CA cells also shows a dose dependence on extracellular Ca(2+) concentration, with significant [Ca(2+)](i) depression being observed in the absence of extracellular Ca(2+). High K(+) significantly increases the JHA release and causes a transient [Ca(2+)](i) increase within seconds in CA cells. High-K(+)-stimulated JHA release is partially inhibited by the benzothiazepine (BTZ)-, dihydropyridine (DHP)- and phenylalkylamine (PAA)-sensitive L-type voltage-dependent calcium channel (VDCC) antagonists diltiazem, nifedipine and verapamil, respectively; by the N- and P/Q-type VDCC antagonist omega-conotoxin (omega-CgTx) MVIIC; and by the T-type VDCC antagonist amiloride. The N-type antagonist omega-CgTx GVIA is the most potent in inhibiting the high-K(+)-stimulated JHA release. No inhibitory effect is shown by the P-type antagonist omega-agatoxin TK (omega-Aga TK). The high-K(+)-induced transient [Ca(2+)](i) increase is largely inhibited by the L-type antagonists (diltiazem, nifedipine, verapamil), by the N- and P/Q-type antagonist omega-CgTx MVIIC and by the T-type antagonist amiloride, and is totally inhibited by the N-type antagonist omega-CgTx GVIA. No inhibitory effect is shown by the P-type antagonist omega-Aga TK. We hypothesize that L-type, N-type and T-type VDCCs may be involved to different degrees in the high-K(+)-stimulated JHA release and transient [Ca(2+)](i) increase in the individual CA cells of the adult male M. loreyi, and that the N-type VDCCs may play important roles in these cellular events.
authors.affiliation: Department of Entomology, National Taiwan University, Taipei, Taiwan, ROC.
authors.forename: Yi-Chun
authors.initials: YC
authors.lastname: Hsieh
authors.forename: En-Cheng
authors.initials: EC
authors.lastname: Yang
authors.forename: Err-Lieh
authors.initials: EL
authors.lastname: Hsu
authors.forename: Yien-Shing
authors.initials: YS
authors.lastname: Chow
authors.forename: Rong
authors.initials: R
authors.lastname: Kou
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000378:metabolism*; D020746:Calcium Channels, L-Type / Q000378:metabolism; D020864:Calcium Channels, N-Type / Q000378:metabolism; D020865:Calcium Channels, P-Type / Q000378:metabolism; D020907:Calcium Channels, Q-Type / Q000378:metabolism; D020747:Calcium Channels, T-Type / Q000378:metabolism; D003335:Corpora Allata / Q000187:drug effects / Q000378:metabolism*; D004553:Electric Conductivity; D005260:Female; D007605:Juvenile Hormones / Q000096:biosynthesis* / Q000378:metabolism; D008297:Male; D009036:Moths / Q000187:drug effects / Q000378:metabolism*; D011188:Potassium
chemical_list: D002121:Calcium Channel Blockers; D015220:Calcium Channels; D020746:Calcium Channels, L-Type; D020864:Calcium Channels, N-Type; D020865:Calcium Channels, P-Type; D020907:Calcium Channels, Q-Type; D020747:Calcium Channels, T-Type; D007605:Juvenile Hormones; D011188:Potassium; D002118:Calcium