The role of signal transducing guanine-nucleotide binding proteins (G-proteins) in α1-receptor mediated smooth muscle contractions was investigated in human hyperplastic prostatic tissue. The selective α1-receptor agonist phenylephrine (PE) evoked dose dependent contractions antagonized by the α1-receptor blockers prazosin (EC50 10 nM) and YM 617 (EC50 3 nM). Application of nifedipine (1–10,000 nM), a blocker of voltage-dependentl-type Ca2--channels (VDCC), inhibited the PE evoked contraction up to 65.4%. Pretreating the tissue strips with pertussis toxin (PTX, exotoxin from Bordetella pertussis; 5–25 μg/ml), inactivating a subpopulation of G-proteins, inhibited the PE induced contractions up to 73.9%. PTX pretreatment had no effect on contractions elicited by 125 mMK-. Application of nifedipine to PTX pretreated tissue led to an additional inhibition of 13.7%. Our findings demonstrate the involvement of PTX-sensitive G-proteins in the signal transduction pathway of α1-receptor induced contractions of prostatic smooth muscle. The remaining contractility of PTX pretreated tissue suggests additional participation of PTX insensitive mechanisms in α1-receptor mediated prostatic smooth muscle contractions.
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Drescher, P., Eckert, R.E. & Madsen, P.O. G-Proteins in alpha1-adrenoceptor mediated prostatic smooth muscle contraction. Urol. Res. 22, 143–146 (1994). https://doi.org/10.1007/BF00571840
- pertussis toxin