A major physiological function of SRIF is to inhibit GH release. SRIF inhibits GH release by activating the receptor subtype sstr2 to inhibit Ca2+ conductance and Ca2+ influx in somatotrophs. This coupling is maintained following continued activation of the receptor, which may explain the resistance of SRIF's inhibition of GH to desensitization. Synthetic peptide analogs of SRIF, such as octreotide and MK 678, are effective inhibitors of GH release. Development of nonpeptide analogs could serve as better drugs than the peptides and be effective inhibitors of hyper GH release, as occurs in acromegaly. Development of sstr2 antagonists could be useful to facilitate GH release, which could prove useful in the treatment of aging and diseases in which muscle mass is lost. Structure function analysis of sstr2 has revealed selective domains of the receptor critical for agonist binding. Such information will be useful in the design and development of new SRIF drugs.
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