Effects of thyroidectomy on the metabolic clearance rate of prolactin and prolactin release in the rat.
The effects of thyroidectomy on both the secretion of rat prolactin (PRL) in vivo and the release of PRL from rat anterior pituitary glands (Aps) in vitro in the absence of ovarian steroids were studied. Rats were ovariectomized (Ovx) 42 days after thyroidectomy or sham-thyroidectomy. On day 15 following ovariectomy the rats were either decapitated for examining the in vitro release of PRL from AP or anesthetized for measuring the metabolic clearance rate (MCR) of rat PRL. After decapitation, blood samples were collected and APs were incubated with or without the extract of rat medial basal hypothalamus (rHE) at 37 degrees C for 4 h. The MCR of iodinated rat PRL was determined by a single injection method. Blood samples were collected by heart puncture at frequent intervals. Serum PRL concentrations of decapitated thyroidectomized-ovariectomized (TX-Ovx) rats were 56% lower than those found in Ovx rats. Thyroidectomy in Ovx rats resulted in a significant reduction of the spontaneous release of PRL from AP. The rHE decreased PRL levels in the medium after incubation with APs from sham Tx rats, but not those from Tx rats. MCR of PRL was reduced in Ovx rats by thyroidectomy. These results indicate that thyroidectomy reduces the spontaneous release of rat PRL by AP and secretion rate of rat PRL in the absence of ovarian steroids.
Pu
H F
HF
Department of Biology, Fu-Jen University, Taipei, Taiwan, Republic of China.
Yang
M Y
MY
Wang
S W
SW
Kao
Y C
YC
Jeng
F S
FS
Wang
P S
PS
D000818:Animals; D005260:Female; D007031:Hypothalamus / Q000502:physiology; D008297:Male; D008657:Metabolic Clearance Rate; D010052:Ovariectomy; D010903:Pituitary Gland, Anterior / Q000187:drug effects / Q000378:metabolism; D011388:Prolactin / Q000097:blood / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D013965:Thyroidectomy; D013972:Thyrotropin / Q000097:blood / Q000378:metabolism; D014020:Tissue Extracts / Q000494:pharmacology
D014020:Tissue Extracts; D011388:Prolactin; D013972:Thyrotropin