Role for calcium in the development of ovarial patency in Heliothis virescens

Insect oocytes sequester nutritive proteins from the hemolymph under the regulation by juvenile hormone (JH), in a process called patency. Here, a pharmacological approach was used to decipher the role for calcium in ovarial patency in the moth, Heliothis virescens. Follicular epithelial cells were exposed in calcium-free or calcium-containing media to JH I, JH II or JH III alone, or in combination with various inhibitors of signal transduction. Protein kinase inhibitors, Na(+)/K(+) -ATPase inhibitor, ouabain, an inhibitor of voltage-dependent calcium channels in plasma membrane, omega-Conotoxin MVII, endoplasmic reticulum (ER) Ca(2+) -ATPase inhibitor, thapsigargin, ER inositol 1,4,5-triphosphate receptor (IP(3)R) inhibitor, 2-ABP and ER ryanodine receptor (RyR) inhibitor, ryanodine, were used. The results of our study suggest that JH II evokes patency via protein kinase C-dependent signaling pathway, and activation of Na(+)/K(+) -ATPase, similar to JH III. Response to JH II and JH III predominantly relies upon external and internal calcium stores, using voltage-dependent calcium channels, IP(3)Rs and RyRs. In contrast, regulation of patency by JH I appears to be largely calcium independent, and the calcium-dependent component of the signaling pathway likely does not use IP(3)Rs, but RyRs only. The JH II, JH III and calcium-dependent component of JH I signaling pathway probably utilize calcium/calmodulin-dependent kinase II for activation of Na(+)/K(+) -ATPase.