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what this all mean??????? figured it would interest some of you!
See : http://news.bmn.com/hmsbeagle/113/notes/feature10
...
Kline and Clevinger found that 50% of the growth hormone present in the
serum of a single donor was bound by the serum prolactin-binding protein
[3]. That this amount would be bound by the prolactin-binding protein might
not have been expected, based on previous investigations of the state in
which growth hormone exists in the circulation: about 45% is bound to growth
hormone-binding protein (the soluble receptor of growth hormone), a few
percent to lower affinity sites and the rest is free [2]. One possibility is
that previous investigations that measured the amount of free growth hormone
underestimated the amount of growth hormone bound to the serum
prolactin-binding protein because of the absence of Zn2+ in those assays,
and that most growth hormone in serum is really bound to proteins, and not
free. Another possibility is that the donor does not have the average
distribution of bound growth hormone; variation among individuals has been
observed [2].
Soluble receptors affect the biological activity of the ligands that they
bind in at least two ways. One is that they prolong the circulation time of
many growth factors and hormones, and therefore provide a more stable pool
of hormone which extends the biological activity. The second effect is that
they reduce the effective concentrations at the membrane receptor by
competing with that receptor for binding to the hormone, which may reduce
the biological activity [1,2]. These two competing effects make it difficult
to predict what the overall physiological effect is in different situations.
The presence of the human prolactin-binding protein will complicate efforts
to understand what occurs with growth hormone, for in the presence of Zn2+,
the extracellular domain of the human prolactin receptor binds human growth
hormone with up to 100-fold higher affinity than human prolactin, and
10-fold higher than human growth hormone binds to the extracellular domain
of its receptor [4]. The serum prolactin-binding protein therefore can be a
potent growth hormone-binding protein. The biological effects of the serum
prolactin-binding protein, whatever they turn out to be, might be as marked
for the biological activities of growth hormone as they are for those of
prolactin.
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See : http://news.bmn.com/hmsbeagle/113/notes/feature10
...
Kline and Clevinger found that 50% of the growth hormone present in the
serum of a single donor was bound by the serum prolactin-binding protein
[3]. That this amount would be bound by the prolactin-binding protein might
not have been expected, based on previous investigations of the state in
which growth hormone exists in the circulation: about 45% is bound to growth
hormone-binding protein (the soluble receptor of growth hormone), a few
percent to lower affinity sites and the rest is free [2]. One possibility is
that previous investigations that measured the amount of free growth hormone
underestimated the amount of growth hormone bound to the serum
prolactin-binding protein because of the absence of Zn2+ in those assays,
and that most growth hormone in serum is really bound to proteins, and not
free. Another possibility is that the donor does not have the average
distribution of bound growth hormone; variation among individuals has been
observed [2].
Soluble receptors affect the biological activity of the ligands that they
bind in at least two ways. One is that they prolong the circulation time of
many growth factors and hormones, and therefore provide a more stable pool
of hormone which extends the biological activity. The second effect is that
they reduce the effective concentrations at the membrane receptor by
competing with that receptor for binding to the hormone, which may reduce
the biological activity [1,2]. These two competing effects make it difficult
to predict what the overall physiological effect is in different situations.
The presence of the human prolactin-binding protein will complicate efforts
to understand what occurs with growth hormone, for in the presence of Zn2+,
the extracellular domain of the human prolactin receptor binds human growth
hormone with up to 100-fold higher affinity than human prolactin, and
10-fold higher than human growth hormone binds to the extracellular domain
of its receptor [4]. The serum prolactin-binding protein therefore can be a
potent growth hormone-binding protein. The biological effects of the serum
prolactin-binding protein, whatever they turn out to be, might be as marked
for the biological activities of growth hormone as they are for those of
prolactin.
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