Release of stored, pre-labeled growth hormone and prolactin from perifused rat pituitary: Effect of human pancreatic growth hormone-releasing factor-44

M. E. Stachura, J. M. Tyler, P. G. Kent, P. K. Farmer

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Abstract

Human pancreatic growth hormone-releasing factor-44 (hpGRF-44) differentially stimulates release of stored and newly synthesized rGH without altering rGH synthesis over 3 h in static in vitro incubation; hpGRF-44 also stimulates release of stored, but not newly synthesized, rPRL. To study the time course of pre-labeled, stored hormone release without pharmacologically interrupting synthesis, the current experiments were performed in perifusion. Fifteen minute pulses of 0.1 to 10 nM hpGRF-44 stimulated stored [3H]rGH release (to 890% of base); 1.0 to 10 nM hpGRF-44 stimulated stored [3H]rPRL release (to 440% of base). Pulses of 0.1 to 1.0 mM (Bu)2 cAMP also stimulated release of [3H]rGH (to 570% of base) and [3H]rPRL (to 410% of base). However, peak [3H]rGH and [3H]rPRL responses to hpGRF-44 required 10 min, while peak responses to (Bu)2 cAMP required 25 min. Continuous hpGRF-44 stimulated an initial surge of stored [3H]rGH release which was not sustained; the diminishing release was not explained by hpGRF-44 degradation. Total radioimmunoassayable (RIA) hormone release roughly paralleled release of stored immunoprecipitable (IPn) hormone. Conclusions: in pituitary perifusion, hpGRF-44 stimulates release of both stored rGH and rPRL as shown in static incubation, but (i) the response is biphasic: in itialrapid release is followed by a progressively lesser response; and (ii) the response isboth more acute and less well sustained than that resulting from exposure to (Bu), cAMP.

Original languageEnglish (US)
Pages (from-to)171-191
Number of pages21
JournalEndocrine Research
Volume12
Issue number2
DOIs
StatePublished - Jan 1 1986

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Growth Hormone-Releasing Hormone
Prolactin
Growth Hormone
Hormones

ASJC Scopus subject areas

  • Endocrinology

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Release of stored, pre-labeled growth hormone and prolactin from perifused rat pituitary : Effect of human pancreatic growth hormone-releasing factor-44. / Stachura, M. E.; Tyler, J. M.; Kent, P. G.; Farmer, P. K.

In: Endocrine Research, Vol. 12, No. 2, 01.01.1986, p. 171-191.

Research output: Contribution to journalArticle

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abstract = "Human pancreatic growth hormone-releasing factor-44 (hpGRF-44) differentially stimulates release of stored and newly synthesized rGH without altering rGH synthesis over 3 h in static in vitro incubation; hpGRF-44 also stimulates release of stored, but not newly synthesized, rPRL. To study the time course of pre-labeled, stored hormone release without pharmacologically interrupting synthesis, the current experiments were performed in perifusion. Fifteen minute pulses of 0.1 to 10 nM hpGRF-44 stimulated stored [3H]rGH release (to 890{\%} of base); 1.0 to 10 nM hpGRF-44 stimulated stored [3H]rPRL release (to 440{\%} of base). Pulses of 0.1 to 1.0 mM (Bu)2 cAMP also stimulated release of [3H]rGH (to 570{\%} of base) and [3H]rPRL (to 410{\%} of base). However, peak [3H]rGH and [3H]rPRL responses to hpGRF-44 required 10 min, while peak responses to (Bu)2 cAMP required 25 min. Continuous hpGRF-44 stimulated an initial surge of stored [3H]rGH release which was not sustained; the diminishing release was not explained by hpGRF-44 degradation. Total radioimmunoassayable (RIA) hormone release roughly paralleled release of stored immunoprecipitable (IPn) hormone. Conclusions: in pituitary perifusion, hpGRF-44 stimulates release of both stored rGH and rPRL as shown in static incubation, but (i) the response is biphasic: in itialrapid release is followed by a progressively lesser response; and (ii) the response isboth more acute and less well sustained than that resulting from exposure to (Bu), cAMP.",
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