Pharmacological analysis of ovarial patency in Heliothis virescens

The insect oocyte sequesters nutritive proteins during patency, which is facilitated as a result of intercellular spaces occurring between follicular epithelial cells under the influence of juvenile hormone (JH). Patency was analyzed in the moth, Heliothis virescens, using a pharmacological approach, in which we used different JH homologues and chemicals that specifically target elements of two second-messenger pathways in vertebrates, the cAMP-dependent and inositol triphosphate/diacylglycerol signaling pathways. JH I and JH Ill evoked dose-dependent patency in H. virescens oocyte follicles, which was suppressed by the Na/K-ATPase inhibitor, ouabain. Patency was observed in follicular epithelial cells treated with either protein kinase C activator, PDBu, or protein kinase A activator, 8-Br-cAMP, by itself. The protein kinase C inhibitor, H-7, preferentially suppressed patency evoked by JH 111, whereas the protein kinase A inhibitor, H89, preferentially suppressed that evoked by JH I. Additionally, patency was triggered by the adenylate cyclase activator, NKH 477, or peptide Gs-protein activator, cholera toxin, alone. Patency evoked by JH I was suppressed by the adenylate cyclase inhibitor, SQ 22,536, and GPAnt-2, a peptide antagonistic to Gs proteins that stimulates adenylate cyclase. Neither of these latter inhibitors, however, affected JH Ill-evoked patency. These results suggest that, in the process of patency in H. virescens ovarial follicles, JH I predominantly signals via the cAMP-dependent second messenger system, whereas JH Ill acts via the inositol triphosphate/diacylglycerol signaling pathway. Moreover, stimulation of patency by cholera toxin alone and inhibition of JH I-evoked patency by GPAnt-2, strongly suggest that JH I acts on the follicular epithelial cells via activation of G-protein, and-possibly-via Gs-protein coupled receptor. (c) 2005 Elsevier Ltd. All rights reserved.