Expression of Muscarinic M sub 3 -Receptors Coupled to Inositol Phospholipid Hydrolysis in Human Detrusor Cultured Smooth Muscle Cells

Authors:
  • BCBoselli C
    Boselli C
  • GSGovoni S
    Govoni S
  • VDVicini D
    Vicini D
  • LCLanni C
    Lanni C
  • RMRacchi M
    Racchi M
  • DGD’agostino G
    D’agostino G
  • MKMarsh K
    Marsh K
  • HDHarriss D
    Harriss D
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Abstract
Purpose: To investigate the effect of muscarinic receptor agonists and antagonists on the accumulation of inositol phosphates in cultures of human detrusor smooth muscle cells. Materials and Methods: Primary explant culture was used to derive smooth muscle cell lines from small bladder biopsies. The cells were loaded with [sup 3 H]-myoinositol, stimulated with muscarinic agonists, and the accumulation of [sup 3 H]-inositol phosphates was measured by liquid scintillation counting. Results: Carbachol (EC 50 8.3 micromolar), methacholine (EC 50, 7.5 micromolar), oxotremorine (EC 50 2.5 micromolar) and pilocarpine (EC sub 50 8.3 micromolar) produced concentration-dependent rises in the accumulation of total [sup 3 H]-inositol phosphates. M 1 (pirenzepine), M sub 2 (methoctramine) and M 3 (4-DAMP and pf-HHSiD) muscarinic receptor antagonists significantly antagonized the response induced by a submaximal concentration of carbachol (100 micromolar). The apparent pA 2 values were atropine (9.4), 4-DAMP (9.2), pfHHSid (7.4), pirenzepine (6.9) and methoctramine (6.3). Conclusions: These results indicate that human detrusor smooth muscle cells in culture express M 3 muscarinic receptors which are linked to phosphoinositide hydrolysis.

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