Ultrastructural cytochemical investigations on adenyl cyclase activity in isoprenaline-treated rat liver

The possibility to demonstrate with cytochemical methods (REIK et al. 1970, HOWELL and WHITFIELD 1972) the activity of adenyl cyclase in rat liver following isoprenaline (IPR) stimulation was evaluated. The drug proved effective as an activator of the enzyme, particularly after in vivo treatment for several days, since it led to the formation of many precipitates which could be ascribed to adenyl cyclase activity, mainly on hepatocyte plasma membranes facing sinusoidal areas. The findings obtained during the experiment, through consistent with the hypothesis of a stimulation of hepatic adenyl cyclase by IPR, pointed out some limitations of the cytochemical techniques now available.