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 III 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 III, 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 III-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 III 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 G(s)-protein coupled receptor.
Pszczolkowski
Maciej A
MA
Department of Entomology, 123 Waters Hall, Kansas State University, Manhattan, 66506, USA. pszcz@ksu.edu
Peterson
Ashley
A
Srinivasan
Asoka
A
Ramaswamy
Sonny B
SB
D000067956:Adenylyl Cyclase Inhibitors; D000818:Animals; D005260:Female; D019204:GTP-Binding Proteins / Q000819:agonists / Q000037:antagonists & inhibitors; D007605:Juvenile Hormones / Q000502:physiology*; D009036:Moths / Q000502:physiology*; D009865:Oocytes / Q000648:ultrastructure; D010053:Ovary / Q000187:drug effects / Q000502:physiology; D012717:Sesquiterpenes / Q000378:metabolism; D015398:Signal Transduction; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism
D000067956:Adenylyl Cyclase Inhibitors; D007605:Juvenile Hormones; D012717:Sesquiterpenes; C008442:juvenile hormone I; C036585:juvenile hormone III; D019204:GTP-Binding Proteins; D000254:Sodium-Potassium-Exchanging ATPase