Stimulation by a TRH precursor, TRH-Gly, of TSH and PRL secretion in rats: effect of starvation.
The hypophysial activities of a possible direct precursor of thyrotropin (TSH)-releasing hormone (TRH), TRH-Gly, were evaluated in estrogen, progesterone-primed rats under urethane anesthesia. Intravenous administration of TRH-Gly in doses of 2-200 micrograms caused a significant and dose-dependent increase in blood TSH and prolactin (PRL). The stimulatory activity of TRH-Gly was 170 to 400-times less potent than that of TRH. The lower potency was confirmed by the action of TRH-Gly on the anterior pituitary cells in vitro. In starved rats, TRH-Gly apparently stimulated TSH and PRL secretion in a dose-dependent manner, and the stimulatory activity increased in starved rats as compared to normal controls. TRH-Gly did not affect [3H-MeHis]TRH binding in pituitary plasma membranes. These data imply that large amounts of TRH-Gly may have significant biological activities and these are potentiated in the starved condition.
Mori
M
M
First Department of Internal Medicine, Gumma University, School of Medicine, Maebashi, Japan.
Murakami
M
M
Iriuchijima
T
T
Miyashita
K
K
Satoh
T
T
Monden
T
T
Michimata
T
T
Kobayashi
I
I
Kobayashi
S
S
D000818:Animals; D002851:Chromatography, High Pressure Liquid; D008297:Male; D010903:Pituitary Gland, Anterior / Q000166:cytology / Q000378:metabolism; D011355:Prodrugs / Q000494:pharmacology*; D011388:Prolactin / Q000097:blood / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D013217:Starvation / Q000097:blood / Q000378:metabolism*; D013972:Thyrotropin / Q000097:blood / Q000378:metabolism*; D013973:Thyrotropin-Releasing Hormone / Q000494:pharmacology
D011355:Prodrugs; D013973:Thyrotropin-Releasing Hormone; D011388:Prolactin; D013972:Thyrotropin