Early effects of PRL on ion conductances in CHO cells expressing PRL receptor
Prevarskaya, N.; Skryma, R.; Vacher, P.; Daniel, N.; Bignon, C.; Djiane, J.; Dufy, B.
American Journal of Physiology 267(2 Pt 1): C554-C562
1994
ISSN/ISBN: 0002-9513 PMID: 7521130 Document Number: 425382
Chinese hamster ovary (CHO-K1) cells were stably, transfected with prolactin (PRL) receptor cDNA. These cells (CHO-E32) expressed the long form of functional PRL receptor. Using microfluorimetric and patch-clamp techniques, we have investigated the effects of PRL on intracellular Ca-2+ concentration ((Ca-2+)-i) and membrane ion conductances. Exposure of CHO-E32 cells to 5 nM PRL resulted in an increase in (Ca-2+)-i. Two types of response were observed: 1) a stimulation of Ca-2+ entry and 2) an intracellular Ca-2+ mobilization. As PRL inhibited voltage-activated Ca-2+ current, the PRL-induced Ca-2+ increase does not involve voltage-activated Ca-2+ channels. PRL also increased a charybdotoxin-sensitive Ca-2+-dependent K+ conductance. Simultaneous measurements showed that PRL hyperpolarized the membrane potential before increasing intracellular Ca-2+ levels. In voltage clamp, hyperpolarizing voltage steps were associated with increased Ca-2+ concentrations, whereas depolarizing voltage steps decreased (Ca-2+)-i. Cell-free patch-clamp experiments showed that PRL directly stimulates K+ channel activity. Our results suggest the existence of a regulatory complex involving a protein kinase tightly associated with the Ca-2+-activated K+ channels and that PRL stimulates these channels by means of the activation of protein kinase. The resulting hyperpolarization stimulates Ca-2+ entry, probably through voltage-insensitive nonspecific channels.