Chlorotetracycline fluorescence associated with plasma membranes of cockroach salivary gland cells

The fluorescent compound chlorotetracycline (CTC) enters the cells of the cockroach salivary gland. The acinar peripheral cells and the non-secretory duct cells become preferentially labelled by CTC. Microscopic examination of the intracellular distribution of CTC indicates that this compound labels the highly folded apical plasma membranes of the peripheral cells and the deep infolds of the basal plasma membranes of the non-secretory duct cells. Lanthanum blocks the entry of CTC into all of the gland cells and in this condition the CTC labels the basal surfaces of the acini and ducts. The results of this investigation support the idea that CTC labels calcium ions in the vicinity of plasma membranes.