Abstract
The adenyl cyclase activity was studied in subcellular preparations (crude membranes:
20,000 × g pellet) of rat, human and ovine adrenals.
In the three species a stimulation by fluoride, ACTH, EDTA and EGTA was found. But
EGTA and EDTA appear to act through different mechanisms. Exogenous calcium inhibits
the basal enzyme activity, but the stimulation induced by ACTH is retained. There
are two pools of endogenous calcium, one inhibits the basal activity of adenyl cyclase,
the other is essential for the stimulation induced by ACTH. Simultaneous examination
of the different factors stimulating adenyl cyclase indicated at least two pools of
enzyme molecules, one stimulated by ACTH, a second by prostaglandins, and possibly
a third by EDTA and EGTA. Sodium fluoride appeared to stimulate a pool common to the
first two pools.
Every tested factor affects maximum velocity of the enzyme without any significant
change of the affinity of ATP for adenyl cyclase.
Key words
Adrenal - Adenyl Cyclase - Prostaglandins - ACTH - EGTA - Calcium
