Enhanced phosphatidylinositol labelling in rat parotid fragments exposed to α-adrenergic stimulation

Abstract

1. Adrenergic agonists provoke a marked increase in labelling of phosphatidylinositol in fragments of rat parotid gland. 2. Adrenaline and phenylephrine (an adrenergic α-agonist) are effective stimulants, but isoprenaline (an adrenergic β-agonist) is relatively ineffective. 3. The response evoked by phenylephrine or adrenaline is prevented by prior incubation of the tissue with phenoxybenzamine (an α-receptor blocking agent), but not by prior incubation with pindolol (a β-receptor blocking agent). 4. Adrenergic stimulation of phosphatidylinositol metabolism in parotid gland is therefore mediated through α-receptors, in common with the adrenaline-induced K+ efflux. It is not linked to enzyme secretion, which is triggered by stimulation of β-receptors. 5. It is suggested that the stimulation of phospholipid metabolism that occurs in several other tissues in the presence of adrenaline or noradrenaline may also involve α-receptors.