Multiple cytosolic calcium signals and membrane electrical events evoked in single arginine vasopressin-stimulated corticotrophs

• Published in: The Journal of biological chemistry 1993-10, Vol.268 (30), p.22313-22321
• Main Authors: Corcuff, J.B., Guérineau, N.C., Mariot, P, Lussier, B.T., Mollard, P
• Format: Article
• Language: English
• Subjects: Animals; Arginine Vasopressin; Arginine Vasopressin - pharmacology; Biological and medical sciences; Calcium; Calcium - metabolism; Calcium Channel Blockers; Calcium Channel Blockers - pharmacology; Cell Membrane; Cell Membrane - drug effects; Cell Membrane - physiology; Cell physiology; Cells, Cultured; Cytosol; Cytosol - metabolism; Dose-Response Relationship, Drug; Fundamental and applied biological sciences. Psychology; Ionomycin; Ionomycin - pharmacology; Isradipine; Isradipine - pharmacology; Kinetics; Life Sciences; Male; Membrane Potentials; Membrane Potentials - drug effects; Membrane Potentials - physiology; Molecular and cellular biology; Pituitary Gland; Pituitary Gland - drug effects; Pituitary Gland - physiology; Rats; Rats, Sprague-Dawley; Signal transduction; Sodium Channel Blockers; Tetrodotoxin; Tetrodotoxin - pharmacology; Time Factors
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1016/S0021-9258(18)41530-X

The action of arginine vasopressin (AVP) on cytosolic free Ca2+ concentration ([Ca2+]i) was investigated in single rat pituitary corticotrophs using indo-1 microfluorimetry, in part in combination with the monitoring of membrane electrical events with the perforated patch-clamp technique. In corticotrophs showing the series of short-lived [Ca2+]i rises (transient pattern) in response to corticotropin-releasing factor, 100 nM AVP evoked either the transient pattern or a [Ca2+]i spike followed by a sustained plateau (spike/plateau pattern). Not all corticotrophs responded to changes in AVP concentration in the same manner. Some cells exhibited a concentration-dependent increase in [Ca2+]i transient activity, whereas others showing the spike/plateau at high AVP concentrations responded to low agonist concentrations by two [Ca2+]i responses: a slow rising step or two to three sinusoidal-like oscillations. Combined [Ca2+]i and patch-clamp recordings as well as manipulation of extracellular Ca2+ showed that both transient pattern and the plateau of spike/plateau response depended on Ca2+ entry mainly through voltage-gated, dihydropyridine-sensitive Ca2+ channels. By contrast, step, oscillations, and spike were due to Ca2+ release from internal stores. These Ca(2+)-mobilizing responses caused the activation of Ca(2+)-activated, apamin-sensitive K+ channels, which led to a membrane hyperpolarization. These results reveal cell-specific [Ca2+]i signals and associated electrical events in individual AVP-stimulated corticotrophs.