Atrial natriuretic factor does not affect basal, forskolin- and CRF-stimulated adenylate cyclase activity, cAMP formation or ACTH secretion, but does stimulate cGMP synthesis in anterior pituitary.

The report that ANF inhibits basal and CRF-stimulated adenylate cyclase activity in anterior pituitary homogenates suggested that the atrial peptide could inhibit ACTH secretion. This possibility was investigated in the ACTH-secreting AtT-20 mouse pituitary tumor cell line as well as homogenates or primary cell cultures from rat anterior hypophysis. ANF (up to 5 X 10(-7) M) was found to be completely ineffective in stimulating basal, CRF- and/or forskolin-stimulated adenylate cyclase activity, cAMP accumulation and ACTH secretion. Similarly, ANF had no effect on spontaneous or GRF-induced GH release from cells in primary culture. ANF receptors, however, are present in AtT-20 cells and anterior pituitary cells as evidenced by the ability of the peptide to stimulate intracellular cGMP accumulation. The data, therefore, suggests that ANF does not have a negative modulatory action on the secretory function of anterior pituitary. The role of cGMP in any other action(s) of ANF remains unknown.