[The mechanism of beta-receptor desensitization in human myometrial culture cell].
Beta-adrenoceptor desensitization is considered to be primarily due to phosphorylation of receptors by protein kinase A (PKA) and beta-adrenaline receptor kinase (beta-ARK) and sequestration of receptors themselves. But in the human uterine muscle, the desensitization mechanism has been evaluated only as a phenomenon, and there are few studies on its mechanism. We evaluated cAMP production by beta-agonist and changes in the number of beta-receptors in cultured human myometrial cells. Uterine muscle cell were obtained from patients with benign disease before menopause and cultured. 1) At the confluent stage, dl-Isoproterenol Hydrochloride (ISP) was added under various conditions, and the intracellular cAMP concentration was determined by EIA. 2) After the addition of ISP (10(-6) M), plates were incubated at 37 degrees C, and beta-AR on the cell membrane surface (S beta-AR) and total beta-AR (T beta-AR) was measured in a binding assay with 125I-pindolol. The production of cAMP dose-dependently increased 30 minutes after the addition of ISP at 10(-6) M or higher, but rapidly decreased thereafter. T beta-AR was similar in the cells treated with ISP (10(-6) M) and the untreated cells. On the other hand, S beta-AR decreased by about 50% in the ISP treated cells. These result suggest the desensitization of beta-AR in human uterine muscle, and the involvement of the sequestration mechanism as its cause.
Okamura
Y
Y
Department of Obstetrics and Gynecology, Nara Medical University.
Oku
M
M
Fujii
E
E
Otsuki
T
T
Adachi
S
S
Morimoto
K
K
D002478:Cells, Cultured; D000242:Cyclic AMP / Q000096:biosynthesis; D005260:Female; D006801:Humans; D007545:Isoproterenol / Q000494:pharmacology; D009215:Myometrium / Q000166:cytology / Q000378:metabolism*; D010766:Phosphorylation; D011943:Receptors, Adrenergic, beta / Q000187:drug effects / Q000378:metabolism*
D011943:Receptors, Adrenergic, beta; D000242:Cyclic AMP; D007545:Isoproterenol