Monensin influences basal and human growth hormone-releasing hormone 44-induced release of stored and new rat growth hormone and prolactin.
When previous data suggested a growth hormone-releasing factor (GRF)-sensitive branch in intracellular hormone processing, the monensin-sensitive Golgi apparatus seemed a likely candidate. We examined monensin's effect on basal and GRF-stimulated release of newly synthesized and stored rat growth hormone (rGH) and rat prolactin (rPRL). 14C-Pre-labeled, perifused rat pituitary fragments were exposed to [3H]leucine in 0-10 microM monensin; a pulse of 3 nM GRF assessed subsequent secretory responsivity. Monensin dose-dependently reduced basal release of stored [14C]rGH and [14C]rPRL. GRF-stimulated release of stored [14C]hormone was doubled after 0.03 microM and 0.1 microM monensin; higher concentrations diminished stored hormone release. Low concentrations of monensin accelerated basal (0.03 microM and 0.1 microM) and GRF-stimulated (0.03 microM) [3H]rGH and [3H]rPRL release without altering recovery; higher monensin concentrations (greater than or equal to 1 microM) reduced basal, and abolished GRF-stimulated, new hormone release and reduced total [3H]rGH and [3H]rPRL recovery. These data are consistent with a GRF-sensitive and monensin-influenced branch in intracellular hormone processing that regulates the fraction of new hormone exiting the cell without prior immersion in storage compartments.
Farmer
P K
PK
Department of Medicine, Medical College of Georgia, Augusta 30912.
Tyler
J M
JM
Stachura
M E
ME
D000818:Animals; D002250:Carbon Radioisotopes; D013006:Growth Hormone / Q000378:metabolism*; D013007:Growth Hormone-Releasing Hormone / Q000494:pharmacology*; D066298:In Vitro Techniques; D008297:Male; D008985:Monensin / Q000494:pharmacology*; D010903:Pituitary Gland, Anterior / Q000187:drug effects / Q000378:metabolism*; D011233:Precipitin Tests; D011388:Prolactin / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains
D002250:Carbon Radioisotopes; D011388:Prolactin; D013006:Growth Hormone; D013007:Growth Hormone-Releasing Hormone; D008985:Monensin