Sustained oscillations in extracellular free Ca2+ were shown to occur on addition of vasopressin, phenylephrine or angiotensin II in isolated rat liver perfused with low (10 microM)-Ca2+ medium. The amplitude and frequency of oscillation depend on hormone concentration. In contrast, Ca2+ releases on addition of ATP, t-butyl hydroperoxide or arachidonate do not exhibit oscillatory behaviour. The vasopressin-induced oscillations were suppressed by glucagon and dibutyryl 3′,5′-cyclic AMP, but not by dibutyryl 3′,5′-cyclic GMP. These observations in the extracellular space complement observations by Woods, Cuthbertson & Cobbold [(1986) Nature (London) 319, 600-602] on oscillations in intracellular free Ca2+ in single liver cells.
