Partial characterization of a thyrotropin releasing hormone-sensitive glycosyl-phosphatidylinositol in pituitary lactotrophes.
Metabolic labelling experiments performed with cultured pituitary lactotrophes revealed the presence of a glycosyl-phosphatidylinositol (GPtdIns) structurally related to GPtdIns lipids isolated from other cell types as demonstrated by: (i) metabolic incorporation of [3H]galactose, [3H]glucosamine and [3H]inositol into the polar inositolphosphoglycan moiety (InsPG) and [3H]myristate and [3H]palmitate into the diacylglycerol (DAG) backbone of GPtdIns; (ii) sensitivity of the [3H]labelled GPtdIns to nitrous acid deamination and; (iii) sensitivity of GPtdIns to phosphatidylinositol (PtdIns)-specific phospholipase C (PLC) hydrolysis. In cultured pituitary cells labelled to isotopic steady state with 10 microCi/ml of [3H]glucosamine, treatment with hypothalamic TRH (10(-6) M) induced a rapid and transient hydrolysis (ca. 50%) of the labelled GPtdIns. Moreover, as demonstrated in [3H]inositol labelled cells, treatment with thyrotropin releasing hormone (TRH) elicited the cleavage of [3H]GPtdIns in a similar manner, and this effect was followed by the phosphoinositide (PtdIns, PtdInsP and PtdInsP2) hydrolysis 30 s later. These results suggest that the phosphodiesterase cleavage of GPtdIns could be an early event implicated in TRH action in pituitary lactotrophes.
Benítez
L
L
Departamento de Endocrinología Celular y Molecular, Universidad de Las Palmas de Gran Canaria, Las Palmas, Spain.
Fanjul
L F
LF
Ruiz de Galarreta
C M
CM
Quintana Aguiar
J
J
González Reyes
J
J
Hernández
I
I
Santana Delgado
P
P
Cabrera Oliva
J
J
Alonso Solís
R
R
Estévez Rosas
F
F
D000818:Animals; D005227:Fatty Acids / Q000378:metabolism; D005260:Female; D017261:Glycosylphosphatidylinositols / Q000032:analysis* / Q000737:chemistry / Q000378:metabolism; D010903:Pituitary Gland, Anterior / Q000737:chemistry* / Q000187:drug effects; D051381:Rats; D017207:Rats, Sprague-Dawley; D013973:Thyrotropin-Releasing Hormone / Q000494:pharmacology*; D013997:Time Factors
D005227:Fatty Acids; D017261:Glycosylphosphatidylinositols; D013973:Thyrotropin-Releasing Hormone