Localisation of potassium pumps inDrosophilaovarian follicles

Abstract

SummaryIt has been shown previously that, inDrosophilaoogenesis, potassium ions are important for bioelectric phenomena as well as for other physiological and development processes. In the present study we determined the spatial distribution and activity of the (Na+, K+)-pump and of ouabain-insensitive K+pumps in plasma membranes of vitellogenic ovarian follicles (stage 10). We used that light micorscopic anthroylouabain method as well as the cytochemical lead and cerium precipitation methods in combination with electron spectroscopic imaging (ESI) and elelctronm energy-loss spectroscopy (EELS). (Na+, K+)-ATPase activity was predominantly observed on the oolemma as well as on the membranes of the columnar follicle cells covering the oocyte, whereas on the membranes of the nurse cells and of the squamous follicle cells covering the nurse cells the activity was vary low. The highset activity of the (Na+K+)-pump was found at the anterior and posterior ends of the oocute, and this on the oolemma as well as on the membranes of the follicle cells located here. Strong activity of ouabain-insensitive K+-pumps was observed on most of the oolemma (except at the anterior of the oocyte) and on the membranes of some nurse cells located next to the oocyte, whereas less activity was found on the other nurse cell membranes and on the membranes of all follicle cells. The suitability of the differnet methods nurse cell membranes and on the membrances of all follicle cells. The suitability of th different methods used for determining the localisation as well as the activity of K+-pumps is discussed. We further discuss the nature of the ouabain-insensitive K+pumps and the relevance of the observed distribution of K+-pumps for K+uptake, extrafollicular ionic current flow intercelluar signalling and other developmental processes inDrosophilaoogenesis.