M, S Nilsson and BO Lund. 1998. Interactions between Methylsulfonyl
PCBs and the Glucocorticoid Receptor. Environmental Health Perspectives.
this paper Johansson et al., are exploring why populations
of gray seals and harbor seals in the Baltic Sea are suffering from
claw deformities, adrenocortical hyperplasia and uterine lesions
suspected to be the result of disruption of glucocorticoid homeostasis.
They find that two common PCB metabolites interact with the glucocorticoid
receptor, but that a third PCB metabolite does not.
humans, excessive production of glucocorticoids can result in obesity,
protein wasting, immunosuppression, insulin resistence (that can
lead to diabetes), osteoporosis, growth retardation and hypertension.
A deficiency of glucocorticoids can result in gastrointestinal problems,
weight loss, mental confusion, hypoglycemia, hypotension and increased
their experiments they examined competition for binding with the
glucocorticoid receptor between the PCBs and dexamethasone, a drug
known to act as a competitive antagonist for the glucocorticoid
receptor. The two active metabolites were MeSO2-CB149 and 3-MeSO2-CB101,
both methylsulphone PCBs. MeSO2-CB149 competed for binding with
dexamethasone with an affinity 10 times lower than 3- MeSO2-CB149.
et al. also note that although these methylsulphonyl PCBs
are two of the most abundant pollutants in Sweden and Canadian biota,
little research has been done to examine their biological effects.
study is significant for two reasons:
It demonstrates the ability of environmental chemicals to interfere
with yet another hormone system, the human cortisol signalling
system, via interference with the glucocorticoid receptor.
The study examines three methysulphonyl PCB metabolites and reports
different binding affinities in two and no binding affinity in
the third. This highlights the complexity of the interaction of
environmental chemicals with the endocrine system. Two chemicals
may be metabolites of the same compound, but due to slight differences
in chemical structure, have significantly different binding affinities
to a hormone receptor.