Calcium channels and basal prolactin secretion in single male rat lactotropes.
Ba2+ currents through voltage-dependent Ca channels and basal prolactin secretion were measured in single, cultured lactotropes by the combined use of whole cell patch-clamp recording and the reverse hemolytic plaque assay. Measurements of plaque area, a cumulative index of the relative amount of prolactin released by a cell per unit time, indicate that lactotropes can be grouped in two main subpopulations that differ in basal secretory activity: small-plaque (SP) cells and large-plaque (LP) cells. Analysis of Ba2+ currents indicates that both SP and LP lactotropes express two types of Ca channels: low-threshold, inactivating, slowly deactivating (SD) channels and high-threshold, noninactivating, fast deactivating (FD) channels. Ba2+ current amplitude is smaller in SP cells than in LP cells. Plaque area, and thus prolactin release, is positively correlated with the density of Ba2+ current through FD channels, but not with that through SD channels. The results suggest that the surface density of functional FD Ca channels in the plasma membrane is a major factor that determines the rate of basal prolactin secretion in single lactotropes.
Cota
G
G
Department of Physiology, Biophysics, and Neurosciences, Centro de Investigacion y de Estudios, Avanzados, Mexico City, Mexico.
Hiriart
M
M
Horta
J
J
Torres-Escalante
J L
JL
D000818:Animals; D015220:Calcium Channels / Q000502:physiology*; D002462:Cell Membrane / Q000502:physiology; D004594:Electrophysiology / Q000379:methods; D006462:Hemolytic Plaque Technique; D066298:In Vitro Techniques; D007700:Kinetics; D008297:Male; D008564:Membrane Potentials; D010903:Pituitary Gland, Anterior / Q000166:cytology / Q000378:metabolism / Q000502:physiology*; D011388:Prolactin / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D013997:Time Factors
D015220:Calcium Channels; D011388:Prolactin