Pathways of alpha 1-adrenergic action: comparison with V1-vasopressin and A1-angiotensin.

The relation between the induction of phosphatidylinositol labelling and ureagenesis by epinephrine (alpha 1-adrenergic action), vasopressin, and angiotensin II was studied in liver cells. It was observed that the alpha 1-adrenergic activation consistently induced a greater stimulation of ureagenesis than the vasopressor peptides. In contrast, vasopressin stimulated phosphatidylinositol labelling to a much greater extent than epinephrine or angiotension II. We suggest that in addition to phosphoinositide turnover, alpha 1-adrenergic action involves other factor(s) in its mechanism of signal transduction.