Burmese Russell's viper venom causes hormone release from rat pituitary cells in vitro

Acute and chronic hypopituitarism is associated with severe envenoming by the Burmese Russell's viper. We have demonstrated that in vitro, Burmese Russell's viper venom (0.1-10 micrograms/ml) causes a dose-dependent release of GH, TSH and ACTH from dispersed rat anterior pituitary cells in culture. At 10 micrograms/ml, venom causes a significant increase in the release of GH (344%, P less than 0.001), TSH (168%, P less than 0.005) and ACTH (greater than 700%, P less than 0.001). We have also shown that the component (or components) responsible for this stimulatory effect is stable to heat (60 degrees C, 1 h) and mild trypsinization. Repeated addition of venom (1 microgram/ml) to pituitary cells in a perifusion column system demonstrated attenuation of GH release. This reduced response was not due to depletion of the GH pool since the pituitary cells were subsequently able to respond to both GH-releasing factor (GRF) stimulation and KCl depolarization. Somatostatin in a dose which abolished GRF-stimulated GH release failed to affect venom-stimulated GH release, implying that venom acts in a cyclic AMP-independent manner. We conclude that Burmese Russell's viper venom has direct effects on pituitary hormone release in vitro. Whether these effects contribute to its known actions in vivo on the function of the pituitary remains to be established.