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 language | English (US) |
---|---|
Pages (from-to) | 171-191 |
Number of pages | 21 |
Journal | Endocrine Research |
Volume | 12 |
Issue number | 2 |
DOIs | |
State | Published - 1986 |
ASJC Scopus subject areas
- Endocrinology