Multiple symmetric lipomatosis has been proposed to be associated with impaired
catecholamine-responsiveness of hypertrophic adipose tissue at the level of
beta-adrenergic receptors or
adenylate cyclase respectively. We have studied the regulation of the
adenylate cyclase by
guanine nucleotides and
adrenaline in 5 subjects suffering from multiple encapsulated
lipomata. In the presence of
GTP (0.1 mmol/l) basal
adenylate cyclase activity averaged 0.5 +/- 0.3 nmol cAMP/mg
protein/10 minutes in normal adipose tissue and 1.0 +/- 0.4 nmol cAMP/mg
protein/10 minutes in hypertrophic adipose tissue respectively. The synthetic
GTP-analogue
GMP(PNP) (0.1 mmol/l) increased non-stimulated activity by about 100% in both tissues.
Adrenaline (1 mumol/l-1 mmol/l) caused a dose-dependent increase of enzymic activity in both tissues which had a maximum of 130% above basal levels in the presence of
GTP and of 300% in the presence of
GMP(PNP) respectively. In one of the six subjects suffering from gluteal
lipomata normal adipose tissue was obtained from the gluteal as well as the abdominal region on two occasions. Maximally effective concentrations of
adrenaline (1 mmol/l) induced a 3-fold increase of enzymic activity in abdominal membranes compared with about a 1.7- and 1.75-fold increase in normal and lipomatous tissue from the gluteal region. The results show that encapsulated
lipomata contain a normally reactive
adenylate cyclase system.