Photodynamic modulation by Victoria Blue BO of phenylephrine-induced calcium oscillations in freshly isolated rat hepatocytes.

The adrenergic agonist phenylephrine (PE) induced typical [Ca2+]i oscillations in freshly isolated rat hepatocytes, and the photodynamic effect of Victoria Blue BO on induced calcium oscillations was investigated. PE induced calcium oscillations disappeared after Victoria Blue BO photodynamic action (in 20 out of 26 experiments), or were present with a decreased amplitude (in 1 out of 26 experiments) or frequency (in 5 out of 26 experiments). After VBBO photodynamic action, the basal calcium level remained at pre-stimulatory level. In comparison, after treatment with the mitochondrial uncoupler CCCP. calcium oscillations disappeared in all experiments, with a significant increase in basal [Ca2+]i. After washing out of CCCP, basal [Ca2+]i returned to pre-stimulation level and calcium oscillations recovered. The photodynamically-induced blockade of calcium oscillations was irreversible, and this effect was present independent of the time interval between VBBO incubation and light illumination. Calcium oscillation blockade was not seen with VBBO in the dark at the concentration used, nor was it seen with light illumination alone. Taken together. it is concluded that VBBO photodynamic action could irreversibly block calcium oscillations in rat hepatocytes, possibly due to blockade of mitochondrion calcium release.