Differences between Male and Female Rats

The relative importance of aand /?-adrenergic pathways and of their respective intracellular mediators, calcium and CAMP, in the stimulation of phosphorylase a induced by catecholamines was studied in hepatocytes isolated from mature male and female rats. The fractional efflux of 46Ca was used as an index of intracellular calcium activity, Our results show that, in females: 1) the activation of phosphorylase a induced by lo-’ to M epinephrine correlates with a rise in cellular C A M P as well as with an increase in 46Ca fractional efflux, 2) both aand 8-agonists stimulate phosphorylase, 3) neither anor &antagonists effectively block the rise in phosphorylase caused by epinephrine, and 4) propranolol suppresses the rise in CAMP while phenoxybenzamine blocks the rise in calcium efflux. On the other hand, we found that in the male: 1) phosphorylase a activity is exclusively correlated with a rise in fractional calcium efflux, 2) epinephrine (IO-’ to lo” M) does not increase CAMP and it causes a greater rise in calcium efflux than in the female at all concentrations, 3) phenylephrine increases calcium efflux and phosphorylase activity without affecting CAMP, 4) phenoxybenzamine totally blocks epinephrine action, and 5) 8-agonists and p-antagonists are without effects. We conclude that, in females, epinephrine utilizes both aand 8-adrenergic pathways which activate phosphorylase by calcium or CAMP, respectively, while, in adult male rats, epinephrine increases phosphorylase a activity by an a-mediated, calcium-dependent and CAMPindependent pathway.