Actinomycin D affects thyrotropin-releasing hormone-induced heterogeneous forms of glycosylated thyroid-stimulating hormone in rat anterior pituitary.
Actinomycin D and cycloheximide were used to clarify the tight relationship between protein synthesis and heterogeneous carbohydrate synthesis of rat pituitary thyroid-stimulating hormone (TSH) under thyrotropin-releasing hormone (TRH) stimulation in vitro. Rat anterior pituitaries were incubated with [3H]glucosamine in the presence of TRH, cycloheximide and actinomycin D at 37 degrees C for 3 and 6 h. The TSH fraction of pituitary homogenates was obtained using affinity chromatography coupled with anti-TSH globulin, and was analyzed by isoelectric focusing. Anterior pituitary in the presence of TRH showed heterogeneous components of [3H]glucosamine-labeled TSH with 6 different isoelectric points (components I-VI). Radioactivities of the components increased with the incubation period. Cycloheximide changed these heterogeneous components. Actinomycin D also caused a striking change in the heterogeneity of pituitary [3H]glucosamine-labeled TSH: components I and II decreased and components III and IV increased as compared to the control group after a 6-hour incubation. The present study implies that actinomycin D affects the TRH-induced heterogeneous components of pituitary TSH glycosylation. The data indicate that messenger RNA is essential for the normal processing of carbohydrate synthesis of pituitary TSH.
Mori
M
M
First Department of Internal Medicine, Gunma University, School of Medicine, Maebashi, Japan.
Michimata
T
T
Yamaguchi
M
M
Yamada
M
M
Iriuchijima
T
T
Kobayashi
S
S
D000818:Animals; D003513:Cycloheximide / Q000494:pharmacology; D003609:Dactinomycin / Q000494:pharmacology*; D006031:Glycosylation; D007525:Isoelectric Focusing; D008297:Male; D010903:Pituitary Gland, Anterior / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D013972:Thyrotropin / Q000096:biosynthesis*; D013973:Thyrotropin-Releasing Hormone / Q000494:pharmacology*
D003609:Dactinomycin; D013973:Thyrotropin-Releasing Hormone; D013972:Thyrotropin; D003513:Cycloheximide