Abstract
Adenlyate cyclase activity in rat adipocyte membranes was studied with special reference
to the effects of adrenalectomy and administration of cortisone acetate in vivo. The
lipolytic hormones ACTH, PTH and noradrenaline were used as stimulators.
Adrenalectomy was accompanied by an increased formation rate of cyclic AMP during
basal conditions, which was maintained even seven days after operation. The response
to hormonal stimulation, measured as the ratio between stimulated and basal values,
was unchanged one day after adrenalectomy but hampered one week postoperatively.
Subcutaneous injection of high doses of cortisone acetate was not accompanied by any
changes in cyclic AMP formation rate under basal conditions or in the responsiveness
to hormonal activation.
Membranes from adrenal deficient or cortisone injected rats exhibited the same sensitivity
to calcium inhibition as the controls. EGTA increased adenylate cyclase activity similarly
in membranes from cortisone treated and sham-operated rats. Membranes from adrenalectomized
animals were only slightly stimulated by calcium deprivation.
It was concluded that glucocorticoid hormones per se do not affect cyclic AMP formation
rates basally or during hormonal activation. However, adipocyte membranes from steroid
deficient rats have a diminished capacity to bind calcium, which secondarily will
affect basal as well as hormonally activated adenylate cyclase activity.
Key words
Adenylate Cyclase - Cyclic AMP - Adrenalectomy - Cortisone - Calcium
