Streptozotocin-induced diabetes in the female rat caused a decrease in the serum level
of somatomedin (Sm), measured by radioreceptor assay. The decrease was reversed by
insulin therapy. In diabetes of varying severity, serum insulin and Sm levels showed
highly significant association up to the insulin concentration (18 μU/ml) corresponding
to normal serum Sm (1 U/ml). Similarly, the hepatic binding of human growth hormone
(hGH) showed highly significant association with serum Sm levels up to the degree
of binding (7 % of tracer) corresponding to normal serum Sm. Binding of hGH to normal
liver was about 12 % of tracer. These results suggest that insulin might regulate
serum Sm via its effect on liver lactogenic receptors, and that about half of these
receptors are “spare”, or in excess of those required to maintain normal serum Sm
levels.
Diabetes
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Insulin
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Somatomedin
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Radioreceptor Assay
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Human Growth Hormone Binding
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Lactogenic Receptors
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Spare Receptors
