Membrane dynamics in the malpighian tubules of the house cricket, acheta domesticus

Abstract

In Acheta domesticus, the Malpighian tubules (Mt) are composed of three morphologically distinct regions (proximal, mid and distal), each consisting of a single cell type. The bulk of the Mt is composed of the midtubule, which shows the greatest response to corticotropin releasing factor-related diuretic peptides (CRF-DP). We know from previous laboratory studies that the second messenger cAMP and its analog dibutyryl cAMP (db-cAMP) cause an approximate doubling in the secretion rate and that this is accompanied by notable ultrastructural changes in the midtubule, especially membrane reorganization in the basal area and extensive vesiculation of the cytoplasm. In this study, we examined the morphological changes in membranes both at the cell surface and internally. By enzymatically removing the basal lamina, we examined the increase in spacing between infolded membranes initiated by db-cAMP stimulation. To examine the intracellular membranes, we used a technique developed for use in invertebrate tissues. This allowed the removal of the cytoplasm for high resolution scanning electron microscopy (HR-SEM) while maintaining the integrity of the lipid constituents of the cell. By using HR-SEM and confocal laser scanning microscopy (CLSM), we gained a unique three-dimensional perspective of the complexity of the internal membrane system of the A. domesticus Mt in both the unstimulated and db-cAMP-stimulated states.