Measurement of CA2+ transients using simultaneous dual-emission microspectrofluorimetry and electrophysiology in individual pituitary cells.

Cytosolic free calcium concentration, [Ca2+]i, was monitored in individual pituitary GH3B6 cells, loaded with the fluorescent Ca2+ indicator indo 1 either by internal perfusion through a patch clamp pipette or by exposure to indo 1 acetoxymethyl ester, with the use of a dual-emission apparatus for microspectrofluorimetry. This system was sensitive enough to allow on-line monitoring of [Ca2+]i (from the ratio of fluorescent intensities) which could be combined simultaneously with whole-cell patch clamp recordings. The following situations were examined: (a) [Ca2+]i oscillations due to action potential firing, and (b) rapid transient elevations of [Ca2+]i triggered by voltage-dependent Ca2+ current. The results indicate that monitoring of [Ca2+]i at the single cell level with indo 1 provides a powerful means to study the [Ca2+]i regulation in pituitary cells, which should be applicable to many other cell types.