@entity597 conjugation limits fluctuations in free XXXX in phaeochromocytoma.

@entity1 @entity935 @entity1425 @entity5 @entity7910 @entity2661 @entity1063 @entity597
More than 80% of total @entity1063 (NA) and @entity1425 (A) and nearly 100% of @entity935 (DA) circulate in blood as @entity7910 , and it has been proposed that @entity597 conjugation contributes to the inactivation of @entity2661 (CA). @entity597 conjugation rapidly responds to changes in sympathetic activity and may buffer the haemodynamic and metabolic consequences of wide fluctuations in CA release in phaeochromocytoma. This hypothesis was tested in seven @entity1 with phaeochromocytoma by consecutive measurements of plasma-free and conjugated NA, under resting conditions, before operation and at least 4 weeks after @entity5 removal. Free and total (free + @entity7910 ) NA were markedly elevated before compared with 1-4 months after surgery. Similar elevations were seen in free and total A and free DA. Before surgery consecutive measurements of total NA, 5 min apart, were markedly different (17 +/- 4.1 and 13.7 +/- 4.4 ng/ml, respectively), whereas only small differences in free NA levels were present (4.1 +/- 1.5 and 4.3 +/- 1.8 ng/ml). These differences between total and free levels were also apparent for A and DA, but to a lesser degree. In three @entity1 , fluctuations in total NA concentration greater than 12 ng/ml were associated with either no change (one @entity1 ) or changes of 0.6 and 2.8 ng/ml in free levels for the other two @entity1 , respectively. Mean blood pressure (BP) varied less than 8 mmHg in these @entity1 . These findings suggest that @entity597 conjugation is a dynamic process which may limit wide fluctuations in free CA concentration during episodic secretory activity in phaeochromocytoma.
