Amyotrophic lateral sclerosis (ALS) is a chronic neurodegenerative disorder of the motor system in the CNS characterized by motor neuron death in the spinal cord, brain stem and cortex. Readily available tissues such as fibroblasts from ALS patients can serve as simple model systems to study the molecular mechanisms leading to degenerative disorders. We have used Fura-2 fluorescence microscopy and single-cell imaging to study the spatiotemporal dynamics of intracellular free calcium ([Ca2+]i) in primary cultures of fibroblasts from skin biopsies from ALS and normal subjects. Increases in [Ca2+]i were induced by stimulation with bradykinin (100 nM); neurotensin (50 nM); N-formyl-Met-Leu-Phe (chemotactic peptide) (1 microM); [Arg8]-vasopressin (1 microM) and histamine (10 microM). The levels of [Ca2+]i in 80-120 individual cells per agonist were monitored for 15 min. No significant differences were found in the resting levels of [Ca2+]i in control (102 +/- 4 nM) and ALS (98 +/- 6 nM) fibroblasts and in the maximal [Ca2+]i levels after stimulation with N-formyl-Met-Leu-Phe, [Arg8]-vasopressin, and histamine. Significantly lower [Ca2+]i transients were found in fibroblasts from ALS donors compared to controls when stimulated with neurotensin (p < 0.002) and bradykinin (p < 0.005). The percentage of individual cells reacting to a given agonist (40-100%) was similar in both groups. The molecular basis of the impaired calcium homeostasis in fibroblasts from ALS patients is not known, but a generalized membrane defect can be excluded since the [Ca2+]i responses are defective only when bradykinin or neurotensin are used as agonists.