Changes in free cytosolic Ca2+ in hepatocytes following alpha 1-adrenergic stimulation. Studies on Quin-2-loaded hepatocytes.
The Ca2+ selective fluorescent indicator, Quin-2, was employed to monitor continuously the concentration of free cytosolic Ca2+ [ Ca2+ ]i in isolated rat hepatocytes. Epinephrine (10(-6) M) and phenylephrine (10(-5) M), acting via alpha 1-adrenergic receptors, increases [ Ca2+ ]i from a basal concentration of approximately 0.2 microM to approximately 0.6 microM. This increase in [ Ca2+ ]i is evident as early as 1 to 1.5 s, the earliest time so far reported for any hepatic alpha 1-adrenergic event. Vasopressin (10(-8) M), after a lag which is 2 to 3 s longer, increases [ Ca2+ ]i to the same extent and at the same rate as the alpha 1-adrenergic agonists. Glucagon (10(-8) M) also increases [ Ca2+ ]i but at a significantly slower rate and only after a lag of about 10 s. All of these agents also induce an increase in the fluorescence of control cells. This Quin-2 independent fluorescence, which is due to an increased reduction of pyridine nucleotides, must be corrected for before the maximum change in [ Ca2+ ]i can be calculated but is sufficiently slow so as not to contribute to the initial rate of increase in the Quin-2-dependent fluorescence.
D000316:Adrenergic alpha-Agonists / Q000494:pharmacology*; D000634:Aminoquinolines; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D003600:Cytosol / Q000378:metabolism; D004837:Epinephrine / Q000494:pharmacology; D005456:Fluorescent Dyes; D066298:In Vitro Techniques; D008099:Liver / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D010646:Phentolamine / Q000494:pharmacology; D010656:Phenylephrine / Q000494:pharmacology; D011433:Propranolol / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D011941:Receptors, Adrenergic / Q000378:metabolism*; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects / Q000378:metabolism*; D014667:Vasopressins / Q000494:pharmacology
D000316:Adrenergic alpha-Agonists; D000634:Aminoquinolines; D005456:Fluorescent Dyes; D011941:Receptors, Adrenergic; D011942:Receptors, Adrenergic, alpha; D014667:Vasopressins; D010656:Phenylephrine; D011433:Propranolol; C035739:Quin2; D002118:Calcium; D004837:Epinephrine; D010646:Phentolamine